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ANTENNA SYSTEMS

Application of FSS Structures to Selectively Control the Propagation of signals into and out of buildings Annex 1: Building design, construction and regulation

M Clift, S Massey

M Shelley

ERA Report 2004-0072 A1 ERA Project 51-CC-12033 FINAL Report

Client : Ofcom Client Reference : AY4464

ERA Report edited and checked by: Approved by:

Martin Shelley Project Manager

Robert Pearson Head of Antenna Systems

March 04Ref. Z:\AS_Projects\Custom Antennas and Consultancy_SW\12033_RA_in_and_out_building_FSS\Reporting\FINAL REPORTING\Annex 1 Building Issues.doc

ERA Report 2004-0072 Annex 1

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Crown copyright 2004. Applications for reproduction should be made to HMSO.

This report has been prepared by ERA Technology Limited and its team for Ofcom under Contract No. AY4464.

DOCUMENT CONTROL

The document may be distributed freely in whole, without alteration, subject to Copyright.

ERA Technology Ltd Cleeve Road Leatherhead Surrey KT22 7SA UK Tel : +44 (0) 1372 367000 Fax: +44 (0) 1372 367099 E-mail: [email protected]

Read more about ERA Technology on our Internet page at: http://www.era.co.uk/


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Contents

Page No.

1. Summary 7

2. Regional distribution of building stock 7

3. Building and Construction Regulations 9 3.1 Building Regulations 9 3.2 The Construction (Design and Management) (CDM) Regulations 1994 23

4. Office building design 25 4.1 Office construction technologies 25 4.2 Building costs 54 4.3 Future trends 56

5. Properties of building materials 60 5.1 Timber products 60 5.2 Glass 62 5.3 Building materials 63 5.4 Summary 63

6. Conclusions 68 6.1 External wall cladding 68 6.2 Structure 70 6.3 Ceilings 70 6.4 Floors 70 6.5 Internal walls 70

7. References 71

8. Acknowledgements 71


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Figure list

Page No.

Figure 1: Shallow floor plate 12 -15 metres 26 Figure 2: Medium depth floor plate 15-20 metres 26 Figure 3: Deep plan floor plate 20 + metres 26 Figure 4: Structural and planning grids [Ref 1] 27 Figure 5: Vertical dimensions 29 Figure 6: Concrete ribbed floor 30 Figure 7: Hollow pot concrete floor 31 Figure 8: Composite concrete and steel floor 31 Figure 9: Concrete columns 32 Figure 10: Concrete beam 32 Figure 11: Flat roof - built up felt on concrete 33 Figure 12: Flat roof - built up felt on steel deck (see also Figure 21 below for composite deck) 33 Figure 13: Flat roof – inverted 34 Figure 14: Pitched roof - metal sandwich system 34 Figure 15: Typical low rise office building (Ref AJPlus) 35 Figure 16: Typical glass-clad building (Ref AJPlus) 36 Figure 17: Typical curtain walling 37 Figure 20: Energy efficient office building 38 Figure 21: External wall of a typical modern office building (Ref AJPlus) 40 Figure 22: Building with cast concrete frame of columns and floor slabs (Ref AJPlus) 41 Figure 23: Building using pre-cast concrete structural panelling system (Ref AJPlus) 42 Figure 24: Load bearing masonry construction 43 Figure 25: Typical three story office building 45 Figure 26: Maximum and minimum storey heights 46 Figure 27: Proprietary external insulation 48 Figure 28: Partial fill Cavity Slab insulation 48 Figure 29: Partial fill insulation – foil faced 49 Figure 30: Full cavity insulation 49 Figure 31: Mineral fibre blown fill 50 Figure 32: Blown polystyrene cavity fill 50 Figure 33: Section through plasterboard partition 51 Figure 34: Plan of plasterboard partition 51 Figure 35: Typical suspended ceiling 52 Figure 36: Typical raised floor detail 53 Figure 37: Double facade of the future 58 Figure 38: Measured dielectric properties of plywood 62 Figure 39: Measured dielectric properties of glass 63 Figure 40: Measured dielectric properties of thermolite block 64 Figure 41: Measured dielectric properties of mortar 65


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Figure 42: Measured dielectric properties of concrete 65 Figure 43: Measured dielectric properties of domestic brick 66 Figure 44: Measured dielectric properties of Rockwool insulation 66 Figure 45: Measured dielectric properties of plasterboard 67 Figure 46: Extent of curtain walling on shallow floor plate 12 -15 metres 68 Figure 47: Extent of curtain walling for medium depth floor plate 15-20 metres 69 Figure 48: Extent of curtain walling for deep plan floor plate 20 + metres 69 Figure 49: Potential Locations of sheet metal in office structures 71

Table list

Page No.

Table 1: Regional Distribution of the Building Stock in England and Wales 1994 7 Table 2: Approved documents 10 Table 3: Schedule 1 of Building Regulations 12 Table 4: Ratio glass to solid 44 Table 5: Office construction costs (source: Building Magazine, February 2003) 54 Table 6: Construction cost elements 55 Table 7: Typical labour and materials breakdown 56 Table 8: NPL data on timber products 61 Table 9: NPL data on glass products 62 Table 10: NPL data on building materials 64 Table 11: Summary of dielectric data 67


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1. Summary

This is Annex 1 to the Final Report provided under Ofcom Contract AY4464, Application of FSS Structures to Selectively Control the Propagation of signals into and out of buildings. It provides background information on the design, construction and regulation of office buildings in the UK.

After a summary of the distribution of building stock in the UK, a detailed appraisal of current building regulations is provided in Section 3. Section 4 describes the most common office building design practices and gives some typical construction costs. The section also identifies trends in building design and the impact that these trends may have on the RF characteristics of the buildings of the future. Section 5 provides details of the electrical properties of many of the key building materials currently used, based on measurements and existing data. Finally, in Section 6, the key features of buildings are considered in the context of allowing or preventing RF propagation.

2. Regional distribution of building stock

Table 1 below provides data on the distribution of building stock in England and Wales, as of 1994. This report is focussed on office buildings.

Table 1: Regional Distribution of the Building Stock in England and Wales 1994

Office Warehouse Factory Total Region County

Number of premises

Area 1,000 m2

Number of Premises

Area 1,000 m2

Number of Premises

Area 1,000 m2

Number of Premises

Area 1,000 m2

Cleveland 2,243 511 2,111 1,402 2,138 1,557 12,364 4,716

Cumbria 2,123 406 2,837 992 3,350 2,228 15,301 4,964

Durham 1,826 311 1,844 1,271 3,351 3,336 13,313 6,113

Northumbria 1,090 171 1,105 644 1,868 1,331 7,255 2,835

Northern

Tyne & Wear

5,486 1,189 3,171 2,215 4,915 4,653 26,272 10,733

Humberside 3,271 582 2,809 2,105 5,320 3,723 21,568 7,913

North Yorkshire

3,509 645 3,512 1,346 4,511 2,653 21,425 6,354

South Yorkshire

4,276 1,004 3,878 3,016 7,071 5,831 28,726 12,571

Yorkshire and Humberside

West Yorkshire

11,005 2,731 10,914 8,015 13,943 14,272 62,183 29,709

Cheshire 4,862 1,068 3,443 2,533 5,083 3,626 23,075 8,780

Greater Manchester

16,002 3,901 11,029 8,692 16,202 15,918 74,696 33,111

Lancashire 4,999 890 5,330 3,560 10,531 8,104 40,211 15,318

North West

Merseyside 5,974 1,341 4,459 2,775 5,554 4,876 33,284 11,485


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Number of premises

Area 1,000 m2

Number of Premises

Area 1,000 m2

Number of Premises

Area 1,000 m2

Number of Premises

Area 1,000 m2

Derby 3,375 595 2,910 1,855 6,846 5,694 22,732 9,411

Leics 4,170 1,050 3,595 3,075 7,969 5,900 25,130 11,444

Lincolnshire 2,307 410 3,242 2,287 6,027 3,095 18,747 6,926

Northants 2,532 652 2,593 3,015 5,025 3,665 15,175 8,050

East Midlands

Nottingham 4,031 924 3,538 2,190 6,391 4,793 24,309 9,464

Hereford & Worcester

3,221 480 2,974 1,544 6,187 3,790 19,089 7,000

Shropshire 1,955 331 1,840 1,082 2,827 2,243 11,121 4,402

Staffordshire 3,654 732 3,730 2,708 6,607 7,242 24,421 12,466

Warwick 2,029 435 1,653 1,281 2,867 2,329 11,352 4,705

West Midlands

West Midlands

11,709 3,058 9,876 7,345 18,102 15,726 67,949 30,604

Cambs 3,814 1,052 3,286 2,204 5,008 2,417 18,018 6,753

Norfolk 3,245 601 4,038 2,344 5,877 2,803 21,753 7,146

East Anglia

Suffolk 3,200 614 2,829 1,609 4,148 2,238 16,463 5,404

Bedfordshire 2,984 702 2,546 1,827 3,050 2,272 13,097 5,629

Berkshire 5,240 2,088 2,223 1,568 3,497 2,057 17,157 7,023

Bucks 3,859 1,172 1 0 5,564 3,800 14,282 5,721

East Sussex 3,405 737 2,291 897 3,407 1,355 19,274 4,497

Essex 6,944 1,427 5,437 3,959 8,673 4,950 36,180 13,171

Greater London

68,564 22,465 27,900 16,119 30,809 12,942 229,850 66,056

Hampshire 7,761 2,108 140 166 11,631 7,057 34,449 11,813

Herts 6,072 1,880 3,188 2,425 4,531 2,950 22,945 9,004

Isle of Wight 408 59 0 0 1,302 577 3,755 914

Kent 7,331 1,364 6,197 3,845 8,178 5,210 38,081 13,122

Oxfordshire 3,294 781 2,075 1,438 2,784 1,460 13,172 4,698

Surrey 6,367 1,891 2,664 1,690 3,675 1,921 23,047 6,965

South East

West Sussex 3,749 936 2,264 1,459 3,655 1,884 17,432 5,517

Avon 5,300 1,518 3,897 2,515 4,368 2,917 24,408 8,920

Cornwall 1,926 254 2,767 633 4,092 1,309 15,804 3,109

Devon 4,659 832 4,940 1,692 5,210 2,790 28,047 7,341

Dorset 3,109 713 995 261 4,942 2,245 17,752 4,687

Gloucs 3,203 727 1,748 906 3,740 2,865 14,334 5,462

Somerset 2,074 309 2,316 955 3,201 1,778 12,634 3,832

South West

Wiltshire 2,745 839 40 32 5,006 3,603 12,801 5,388


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Number of premises

Area 1,000 m2

Number of Premises

Area 1,000 m2

Number of Premises

Area 1,000 m2

Number of Premises

Area 1,000 m2

Clwyd 1,628 272 1,629 1,445 2,733 2,837 10,730 5,165

Dyfed 1,271 174 1,607 580 2,359 957 9,965 2,279

Gwent 1,808 274 1,563 1,019 2,663 2,477 10,812 4,514

Gwynedd 888 152 1,313 679 1,517 764 7,920 2,119

Mid Glamorgan

1,436 256 1,457 562 2,888 2,754 11,263 4,287

Powys 588 79 524 222 1,210 696 3,957 1,174

South Glamorgan

3,206 802 1,449 857 1,640 1,231 11,106 3,800

Wales

West Glamorgan

1,668 242 1,098 517 1,946 1,847 8,617 3,296

ENGLAND AND WALES

277,395 70,736 186,815 119,372 305,989 213,552 1,358,803 497,879

3. Building and Construction Regulations

Two key regulations need to be taken into account when designing and constructing buildings – the Buildings Regulations 2000 and the Construction (Design and Management) Regulations 1994. Both are associated with the health and safety of the users and persons nearby and those who are going to build and maintain the building.

3.1 Building Regulations

3.1.1 Background to the regulations

The Building Regulations are made under powers provided in the Building Act 1984, and apply in England and Wales. The current edition of the regulations is The Building Regulations 2000 (as amended) and the majority of building projects are required to comply with them. They exist to ensure the health and safety of people in and around all types of buildings (i.e. domestic, commercial and industrial). They also provide for energy conservation and for access and facilities for disabled people.

The Building Regulations Division of the Office of the Deputy Prime Minister is responsible for the formulation of the regulations and prioritising and programming reviews of the regulations.

The Building Regulations Advisory Committee (BRAC), which is categorised as an ‘advisory non departmental public body,’ advises the Secretary of State on the exercise of his power to make Building Regulations. In practice, BRAC is consulted on all matters concerned with changes to the Building Regulations, both technical and procedural.


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The main work of BRAC is conducted in five committee meetings per year; while advice on more technical aspects is developed and carried forward through working parties comprising BRAC members, co-opted members where appropriate, and officials of the Building Regulations Division. The main BRAC meetings are attended by observers from other government departments and advisory organisations including the Foundation for the Built Environment, of which BRE is a wholly owned subsidiary. Ideas for new regulations or changes to existing ones are handled by the Building Regulations Division.

Builders, developers and owners are required by law to obtain building control approval; this is an independent check that the Building Regulations have been complied with. There are two types of building control providers, the Local Authority and Approved (private) Inspectors. Practical guidance on ways to comply with the functional requirements in the Building Regulations is contained in a series of Approved Documents.

Each Document contains: • general guidance on the performance expected of materials and building work in order to

comply with each of the requirements of the Building Regulations; • practical examples and solutions on how to achieve compliance for some of the more

common building situations – deemed to satisfy.

The Approved Documents are grouped as follows:

Table 2: Approved documents

Approved Document (AD) Content

Approved Document A Structure

Approved Document B Fire safety

Approved Document C Site preparation and resistance to moisture

Approved Document D Toxic substances

Approved Document E Resistance to passage of sound

Approved Document F Ventilation

Approved Document G Hygiene

Approved Document H Drainage and waste disposal

Approved Document J Combustion appliances and fuel storage systems

Approved Document K Protection from falling collision and impact

Approved Document L1/2 Conservation of fuel and power

Approved Document M Access to and use of buildings

Approved Document N Glazing

Approved Document for Regulation 7

Workmanship


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The guidance in the documents does not amount to a set of statutory requirements and does not have to be followed if the designer or builder wants to carry it out in some other way, providing it can be shown that it still complies with the relevant requirements. The guidance will be taken into account when the Building Control Service is considering whether the plans of the proposed work, or work in progress, comply with particular requirements.

However, there is a legal presumption that, if the guidance has been followed, this is evidence that the work has complied with the Building Regulations. It is the job of the Building Control Service to consider whether the plans and work comply with the relevant requirements in Schedule 1 to the Building Regulations and not whether they necessarily follow the specific guidance or a specific example in an Approved Document.

‘Building Work’ is defined in Regulation 3 of the Building Regulations. The definition means that the following types of work amount to ‘Building Work’:

• erection or extension of a building; • installation or extension of a service or fitting which is controlled under the regulations; • alteration project involving work which will be relevant to the continuing compliance of the

building, service or fitting with the requirements relating to structure, fire, or access and facilities for disabled people;

• insertion of insulation into a cavity wall • underpinning of the foundations of a building.

It is noted that there are currently no regulations covering the RF characteristics of buildings. As stated above, the regulations exist to ensure the health and safety of people in and around all types of buildings. Given this remit, it is believed that a strong argument could be made that access to mobile communications networks while inside buildings, either for use by the general public or by emergency services, could be regarded as a health and safety issue and hence could fall within the general aims of the regulations. Hence, in the future, the development of additional regulations covering this aspect could be foreseen.

3.1.2 Summary of approved documentation

Table 3 provides the wording of the Schedule 1 to the building Regulations 2000 with a brief explanation of each.


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Table 3: Schedule 1 of Building Regulations

Schedule 1 of Building Regulations 2000 - requirements

Explanatory note

Approved Document A - Structure A1 Loading

(1) The building shall be constructed so that the combined dead, imposed and wind loads are sustained and transmitted by it to the ground - (a) safely; and (b) without causing such deflection or deformation of any part of the building, or such movement of the ground, as will impair the stability of any part of another building.

(2) In assessing whether a building complies with sub-paragraph (1) regard shall be had to the imposed and wind loads to which it is likely to be subjected in the ordinary course of its use for the purpose for which it is intended.

This requirement gives basic parameters for the structural design of mainly domestic scale traditionally constructed buildings – ie masonry walls and concrete foundations, timber roofs and floor construction

Section 1 Sizes of structural elements for certain residential buildings and other small buildings of traditional construction

Mainly only relevant to domestic and small scale buildings

Section 2 External wall cladding

This section is primarily concerned with heavy cladding systems such as concrete panels, but some aspects are applicable to lightweight curtain walling. It provides guidance on supporting and fixing of external wall cladding which would present a hazard if it became detached.

It sets out four basic requirements for cladding:

• it must safely support dead, imposed and wind loads and transfer them to the structure

• it should be securely fixed • there should be provision for accommodating differential movement

between the cladding and structure • the cladding and its fixings should be of durable materials - the

fixings need a service life at least equal to the life of the cladding.

It notes that where the wall cladding is required to support other fixtures eg antennae, full account should be taken of the loads and forces arising from them.

Section 3 Re-covering of roofs

This acknowledges the fact that because a new roof covering may be heavier or lighter than the one it is replacing, the supporting roof structure should be inspected to ensure it is capable of sustaining the new load.

Section 4 Codes standards and references for Requirements A1 and A2

This section lists codes, standards and other references for structural design and construction of all buildings. It includes those relevant to loading, structural work for timber, masonry, reinforced, pre-stressed or plain concrete, steel, aluminium, foundations, ground movement and existing buildings.

A2 Ground movement

The building shall be constructed so that ground movement caused by - (a) swelling, shrinkage or freezing of the subsoil; or (b) land-slip or subsidence (other than subsidence arising from shrinkage), in so far as the risk can be reasonably foreseen, will not impair the stability of any part of the building.

(a) Although not directly referenced, this refers to the effect that expansion and construction of subsoil could have on the stability of the structure

(b) In Section 4 Codes standards and references for Requirements A1 and A2, there is also information on a series of reviews and geotechnical conditions carried out under Government sponsorship covering land slip and subsidence.

A3 Disproportionate collapse

The building shall be constructed so that in the event of an accident the building will not suffer collapse to an extent disproportionate to the cause.

This requirement applies only to a building having five or more storeys (each basement level being counted as one storey) excluding a storey within the roof space where the slope of the roof does not exceed 70° to the horizontal.

This sets out how to approach disproportionate collapse such as the accidental removal of a support. The collateral impact should be not be disproportionate – considered to be not more than 15% of the area of a floor or 70 sq m whichever is less.


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Explanatory note

Approved document B - Fire safety

B1 Means of warning and escape

The building shall be designed and constructed so that there are appropriate provisions for the early warning of fire, and appropriate means of escape in case of fire from the building to a place of safety outside the building capable of being safely and effectively used at all material times.

The regulation considers three building types in this section – dwelling houses, flats and maisonettes, and buildings other than dwellings eg office buildings.

Means of escape to a place of safety outside the building is considered under horizontal escape and vertical (staircase) travel to an exit. The regulation makes reference to BS 5588 Fire precautions in the design and construction of buildings.

Most office buildings over one storey high are designed with two or more protected staircases leading directly to the outside. The actual number of stairs is dictated by travel distances, the need to avoid dead ends - where there is only access to one stair which may be blocked - and the number of occupants on a floor.

In an office building, the maximum travel distance where escape is possible in more than one direction is 45 metres although there are some other issues that might reduce this to 30 metres and 18 metres for a single stair situation.

Corridor widths are determined by the number of persons needing to use them and are the minimum width between any fixed obstructions and measured at 1500mm above the floor level. Handrails can protrude by up to 100mm.

Stairway widths are determined by the numbers using them and the floors being served.

The main structure, escape corridors and stairways are protected from fire - see B3.

B2 Internal fire spread (linings)

(1) To inhibit the spread of fire within the building the internal linings shall - (a) adequately resist the spread of flame over their surfaces; and (b) have, if ignited, a rate of heat release which is reasonable in the circumstances.

(2) In this paragraph "internal linings" mean the materials lining any partition, wall, ceiling or other internal structure.

There are three classes of lining materials - 3, 1 and 0, which is the ‘best’ or least combustible. The choice of materials for walls and ceilings can have a significant effect on the spread of fire and its rate of growth – even though they may not be the initial cause of the fire. This is very important in circulation spaces and escape routes where rapid spread could prevent occupiers from escaping.

However the provisions do not generally apply to the finishes of floors and stairs because they are not involved in a fire until it is well under way. In any case the stairway is protected from fire for a given period, therefore until people should have escaped.

Class 0 is appropriate for escape routes. Thin facings (0.5 mm or less) do not generally affect the classifications so walls and ceilings can be papered. Use of thicker laminates needs to be substantiated by tests.

There are two properties of lining material that influence fire spread – the rate of flame spread over the surface when it is subjected to intense radiant heat and the rate at which it gives off heat when burning. Generation of smoke and fumes must also be considered – although not covered by this Regulation.

B3 Internal fire spread (structure)

(1) The building shall be designed and constructed so that, in the event of fire, its stability will be maintained for a reasonable period.

(2) A wall common to two or more buildings shall be designed and constructed so that it adequately resists the spread of fire between those buildings. For the purposes of this sub-paragraph a house in a terrace and a semi-detached house are each to be treated as a separate building.

(1) Under fire conditions, the premature failure and collapse of the structure of a building can be avoided by designing the structural load bearing elements to have a minimum standard of fire resistance, in order to;

• minimise the risk to the occupants, some of whom may have to wait for some time during evacuation - particularly if the building is a large one;

• reduce the risk to fire fighters, on search or rescue operations • reduce the danger to people in the vicinity of the building, from falling

debris or the impact of a collapsing structure on nearby buildings.

Load bearing elements include structural frames, floors and load bearing walls.

The roof and the bottom floor are not normally treated as structure under this regulation. The structure which supports the roof need not be fire resistant - except where it is supporting an external wall.


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Explanatory note

B3 Internal fire spread (structure), continued

Cladding which transmits only self-weight and wind loads may need fire resistance to satisfy the need to prevent spread of fire beyond a boundary.

The structure in an office building would normally have a minimum period of fire resistance of 30, 60, 90 or 120 minutes depending on height.

Compartment walls/floors, which are the fire-resisting walls and floors used to separate one fire compartment from another, are treated as structure for the purpose of this regulation, even though they are not necessarily load bearing – see (3).

(3) To inhibit the spread of fire within the building, it shall be sub-divided with fire-resisting construction to an extent appropriate to the size and intended use of the building.

(3) The spread of fire within a building can be controlled by sub-dividing it into compartments separated from one another by walls and/or floors of fire-resisting construction. This prevents rapid fire spread which could trap occupants of the building; and reduces the chance of fires becoming large.

Openings through compartment walls and floors should be minimised and fitted with fire resistant doors to the same standard.

Holes for services should be: • sealed with eg intumescent sealants, • sleeved or fitted with fire dampers in the case of air ducts, or the services are made from a suitable non-combustible material such as cast iron or steel.

(4) The building shall be designed and constructed so that the unseen spread of fire and smoke within concealed spaces in its structure and fabric is inhibited.

(4) Voids above other spaces in a building, such as above a suspended ceiling, below a raised floor, in a roof space or within a cavity walling/cladding system, can provide a ready route for smoke and flame spread. Cavity barriers are fitted at intervals to restrict the spread. Openings through them should be kept to a minimum and should be treated generally in the same manner as penetrations through compartment walls

B4 External fire spread

(1) The external walls of the building shall adequately resist the spread of fire over the walls and from one building to another, having regard to the height, use and position of the building.

(1) This sets out requirements to restrict the radiant heat of a fire in one building spreading the fire to other buildings nearby. The height of the building and the distance from the boundary dictate the amount of unprotected area of the external wall, such as doors and windows.

There are requirements for restricting the combustibility of external walls to minimise the chances of them being ignited from an outside source and from spreading fire up the external face of the building.

(2) The roof of the building shall adequately resist the spread of fire over the roof and from one building to another, having regard to the use and position of the building.

(2) This sets out rules aiming to prevent fire spreading from one building to another across the roof or from burning material landing on the roof.

B5 Access and facilities for the fire service

(1) The building shall be designed and constructed so as to provide reasonable facilities to assist fire fighters in the protection of life.

(2) Reasonable provision shall be made within the site of the building to enable fire appliances to gain access to the building.

In low rise buildings without deep basements access for fire brigade can be met by a combination of the normal means of escape, and the measures for vehicle access which facilitate ladder access to upper storeys.

In other buildings the problems of reaching the fire, and working inside near the fire, need additional facilities to avoid delay in getting to the seat of the fire and to provide a safe operating base near to it. These additional facilities include fire fighting lifts, fire fighting stairs and fire fighting lobbies, which are combined in a protected shaft.

Approved Document C - Site preparation and resistance to moisture

C1 Preparation of site

The ground to be covered by the building shall be reasonably free from vegetable matter.

Turf and vegetable matter needs to be removed from the ground to be covered by a building to a sufficient depth in order to prevent later growth.

Below ground services such as drainage, gas and water supplies should be strong or flexible enough to cope with roots. Joints should resist penetration by roots.


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Explanatory note

C2 Dangerous and offensive substances

Reasonable precautions shall be taken to avoid danger to health and safety caused by substances found on or in the ground to be covered by the building.

If gaseous or solid contaminants are present they need to be removed, the building sealed from the source, or filling under the building with a material that will not adversely react to the contaminant. Gases such as radon and methane should be vented away from under the building.

C3 Subsoil drainage

Adequate subsoil drainage shall be provided if it is needed to avoid (a) the passage of the ground moisture to the interior of the building; (b) damage to the fabric of the building.

Ground covered by buildings should be drained if the ground water could affect the building fabric. Otherwise the design of the building must be able to prevent ground water from entering the building or passing to materials that would be adversely affected by water.

C4 Resistance to weather and ground moisture

The walls, floors and roof of the building shall adequately resist the passage of moisture to the inside of the building.

Moisture from the ground floor must be stopped from reaching the inside through walls and floors – rising damp. Moisture from rain and snow must be prevented from reaching the inside by the roof and walls – ie rain penetration. Moisture, including water vapour, must not be allowed to damage a material or structure to the point that it would create a danger to health or safety. It must not be allowed to permanently reduce the performance of insulating material.

Approved Document D - Toxic substances

D1 Cavity insulation

If insulating material is inserted into a cavity in a cavity wall reasonable precautions shall be taken to prevent the subsequent permeation of any toxic fumes from that material into any part of the building occupied by people.

This is to ensure that the risk to health of persons in buildings is reduced from formaldehyde fumes given off by urea formaldehyde cavity foam installations.

Approved Document E - Resistance to the passage of sound

E1 Protection against sound from other parts of the building and adjoining buildings

Dwelling-houses, flats and rooms for residential purposes shall be designed and constructed in such a way that they provide reasonable resistance to sound from other parts of the same building and from adjoining buildings.

E2 Protection against sound within a dwelling-house etc.

Dwelling-houses, flats and rooms for residential purposes shall be designed and constructed in such a way that – • internal walls between a bedroom or a room

containing a water closet, and other rooms;and • internal floors, provide reasonable resistance to sound.

E3 Reverberation in the common internal parts of buildings containing flats or rooms for residential purposes

The common internal parts of buildings which contain flats or rooms for residential purposes shall be designed and constructed in such a way as to prevent more reverberation around the common parts than is reasonable.

E4 Acoustic conditions in schools

Each room or other space in a school building shall be designed and constructed in such a way that it has the acoustic conditions and the insulation against disturbance by noise appropriate to its intended use.

For the purposes of this Part - “school” has the same meaning as in section 4 of the Education Act 1996[4]; and “school building” means any building forming a school or part of a school.

Requirement E of the regulations covers resistance to the passage of sound. The requirements of this part only apply to residential buildings (including in this case, hotels and the like) and to schools and not to offices.


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Explanatory note

Approved Document F - Ventilation F1 Means of ventilation There shall be adequate means of ventilation provided for people in the building.

The provisions described in the guidance are aimed at: • extracting water vapour and other pollutants from where they arise in

the building • enabling rapid dilution of damp or polluted air • providing a continuous supply of fresh air to the building by natural means, mechanical ventilation or, in non-domestic buildings, air conditioning systems.

Guidance is given in two sections applying to domestic and non-domestic buildings respectively. The notes that follow concern the non-domestic guidance.

The guidance is presented as a set of recommendations of general application, augmented by particular advice for spaces used for special purposes and for car parks.

In the general recommendations, ventilation parameters are offered according to the purpose of the space: • sizes and design features are given for openable windows and for

ventilators intended for rapid ventilation and background ventilation by natural means;

• extract rates for mechanical ventilators and their controls are described where (in rooms such as kitchens and bathrooms) they are recommended as an additional provision or where they wholly or partially replace the natural ventilation (including where rooms cannot have windows owing to their location)

Particular parameters are given for spaces where people congregate in large numbers. The use of passive stack ventilation is acknowledged in place of some fans.

Where certain specialist activities take place, the document advises that requirement F1 can by complied with by following design guidance in other sources. References are offered for: • workplaces and in particular building services plant rooms • commercial kitchens

There is also special guidance for the ventilation of smoking rooms

ADF cites external references for the design of mechanical ventilation/air conditioning plant, and identifies sources of contamination that designers should seek to avoid when locating air inlets for such systems.

F2 Condensation in roofs Adequate provision shall be made to prevent excessive condensation -

(a) in a roof; or (b) in a roof void above an insulated ceiling.

The aim of the guidance is that condensation should be controlled such that it does not degrade the performance of thermal insulation and the structure.

Guidance is given on the ventilation of the space above the insulation in pitched and flat roofs. Depending on the roof design, this may entail purpose made ventilation openings of specified size at the eaves and at the ridge. For flat roofs (and roofs containing accommodation where the insulation follows the pitch of the roof) minimum heights are specified for the void above the insulation.

Approved Document G - Hygiene G1 Sanitary conveniences and washing facilities

(1) Adequate sanitary conveniences shall be provided in rooms provided for that purpose, or in bathrooms. Any such room or bathroom shall be separated from places where food is prepared.

(2) Adequate washbasins shall be provided in (a) rooms containing water closets; or (b) rooms or spaces adjacent to rooms containing water closets.

Any such room or space shall be separated from places where food is prepared.

The Building Regulations Requirement G1states the need to provide adequate and cleanable sanitary conveniences and their associated washing facilities, supplied with hot and cold water and installed in suitable rooms away from food preparation areas.

The corresponding guidance in ADG describes the minimum facilities to meet the requirement and how they should be accommodated in relation to kitchens etc. It describes in rather general terms the desirable characteristics of fittings - for cleanliness, and the essential features of the water supply and waste discharge.


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Explanatory note

(3) There shall be a suitable installation for the provision of hot and cold water to washbasins provided in accordance with paragraph (2).

(4) Sanitary conveniences and washbasins to which this paragraph applies shall be designed and installed so as to allow effective cleaning.

G2 Bathrooms

A bathroom shall be provided containing either a fixed bath or shower bath, and there shall be a suitable installation for the provision of hot and cold water to the bath or shower bath.

This requirement of the building regulations applies only to dwellings and is not therefore relevant to offices

G3 Hot water storage

A hot water storage system that has a hot water storage vessel which does not incorporate a vent pipe to the atmosphere shall be installed by a person competent to do so, and there shall be precautions -

(a) to prevent the temperature of stored water at any time exceeding 100°C; and (b) to ensure that the hot water discharged from safety devices is safely conveyed to where it is visible but will not cause danger to persons in or about the building.

This requirement concerns the safe installation of unvented hot water storage vessels. Technical guidance on how this can be achieved is offered in ADG in two sections, depending upon the size and power rating of the system.

Systems up to 500 litres and 45kW

Such storage systems are to be approved proprietary units installed by competent persons. They should incorporate on of the measures to prevent overheating of the water as specified in the document. Recommendations are made for the pipework to carry away water discharged by safety systems. Pipe sizes and routes are described. Discharge pipes should be of metal and, although not a specific recommendation, could typically terminate outside of the building.

Systems over 500 litres or over 45kW

It is acknowledged that these will be individually designed systems inappropriate for type approval. Recommendations are given for their design which essentially mirror the guidance for the smaller systems.

Approved Document H - Drainage and waste disposal H1 Foul water drainage

(1) An adequate system of drainage shall be provided to carry foul water from appliances within the building to one of the following, listed in order of priority- • a public sewer; or, where that is not reasonably

practicable, • a private sewer communicating with a public sewer;

or, where that is not reasonably practicable, • either a septic tank which has an appropriate form of

secondary treatment or another wastewater treatment system; or, where that is not reasonably practicable,

• a cesspool.

(2) In this Part “foul water” means waste water which comprises or includes - • waste from a sanitary convenience, bidet or

appliance used for washing receptacles for foul waste; or

• water which has been used for food preparation, cooking or washing.

Much of the guidance in ADH in relation to the Requirement H1 concerns the design and construction of suitable sanitary pipe work in buildings and the drains to which the sanitary pipe work connects, the latter running within the building's grounds and the surrounding lands. The aim is a system which performs at minimal risk of blockage and leakage and which prevents foul air re-entering the building. It is to be ventilated, cleanable and should not increase the susceptibility of the building to flooding.

Design details for the sanitary pipe work include restrictions on the route of the system, suitable pipe diameters and gradients and connection details. Provisions to avoid syphonage are described including ventilation arrangements. Clearances between windows and ventilation openings into the system are specified.


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Explanatory note

H2 Waste water treatment systems and cesspools

(1) Any septic tank and its form of secondary treatment, other wastewater treatment system or cesspool, shall be so sited and constructed that - • it is not prejudicial to the health of any person; • it will not contaminate any watercourse,

underground water or water supply; • there are adequate means of access for emptying and

maintenance; and • where relevant, it will function to a sufficient

standard for the protection of health in the event of a power failure.

(2) Any septic tank, holding tank which is part of a wastewater treatment system or cesspool shall be - • of adequate capacity; • so constructed that it is impermeable to liquids; and • adequately ventilated.

(3) Where a foul water drainage system from a building discharges to a septic tank, wastewater treatment system or cesspool, a durable notice shall be affixed in a suitable place in the building containing information on any continuing maintenance required to avoid risks to health.

H3 Rainwater drainage

(1) Adequate provision shall be made for rainwater to be carried from the roof of the building.

(2) Paved areas around the building shall be so constructed as to be adequately drained.

H4 Building over sewers

(1) The erection or extension of a building or work involving the underpinning of a building shall be carried out in a way that is not detrimental to the building or building extension or to the continued maintenance of the drain, sewer or disposal main.

(2) In this paragraph “disposal main” means any pipe, tunnel or conduit used for the conveyance of effluent to or from a sewage disposal works, which is not a public sewer.

(3) In this paragraph and paragraph H5 “map of sewers” means any records kept by a sewerage undertaker under section 199 of the Water Industry Act 1991 (a).

H5 Separate systems of drainage

Any system for discharging water to a sewer which is provided pursuant to paragraph H3 shall be separate from that provided for the conveyance of foul water from the building.

H6 Solid waste storage

(1) Adequate provision shall be made for storage of solid waste.

(2) Adequate means of access shall be provided - • for people in the building to the place of storage;

and • from the place of storage to a collection point

(where one has been specified by the waste collection authority under section 46 (household waste) or section 47 (commercial waste) of the Environmental Protection Act 1990(b) or to a street (where no collection point has been specified).

Requirements H2 to H6 inclusive: The guidance given in ADH in relation to the latter five requirements has practically no special bearing on the internal design of buildings or the services within them.


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Explanatory note

Approved Document J - Heat producing appliances J1 Air supply Combustion appliances shall be so installed that there is an adequate supply of air to them for combustion, to prevent overheating and for the efficient working of any flue.

J2 Discharge of products of combustion Combustion appliances shall have adequate provision for the discharge of products of combustion to the outside air.

J3 Protection of building Combustion appliances and flue pipes shall be so installed, and fireplaces and chimneys shall be so constructed and installed, as to reduce to a reasonable level the risk of people suffering burns or the building catching fire in consequence of their use.

J4 Provision of information Where a hearth, fireplace, flue or chimney is provided or extended a durable notice containing information on the performance capabilities of the hearth, fireplace, flue or chimney shall be affixed in a suitable place in the building for the purpose of enabling combustion appliances to be safely installed.

The first four of these requirements are intended to ensure that combustion appliances may be used safely in buildings with minimal risks to occupants as a result of the contamination of the indoor air by the products of combustion or due to high temperatures.

The requirements apply to all buildings. However, the guidance in ADJ is primarily meant to be applied to “domestic scale” installations and its scope is limited to installations of less than: 75kW input rating for gas-fired installations; 50 kW and 45 kW rated output for solid fuel and oil-fired installations respectively.

The corresponding guidance in ADJ is carried in four sections of which the first is of general application whilst the remainder (Sections 2,3,4) deal respectively with the particular measures to take for solid-fuel, gas and oil-fired appliances.

Where ventilators are needed to supply appliances with air from outdoors or distribute it internally, guidance is given on ventilator sizing, design and location. Measures are described to avoid extract fans installed for other purposes creating pressure gradients incompatible with appliance operation.

The document provides a substantial amount of detail on the design of flues. This includes flue cross sectional areas for various appliance types, flue heights, maximum offset angles and the design and location of flue outlets. The latter are given as separations from boundaries and features of the building envelope such as windows.

Suitable products and constructional details are given for fluepipes and chimneys constructed in masonry, pre-cast flue blocks and prefabricated metal systems. Methods of testing flue condition are described along with products and techniques for their refurbishment.

The need to segregate appliances and their flues from combustible materials and from people is addressed, with minimum wall thicknesses for chimneys, restrictions on the paths to be taken by flues and with guidance on the design of hearths and fireplaces.

A suitable data plate is described, for display in the building, listing the characteristics of installed flues and hearths.

J5 Protection of liquid fuel storage systems Liquid fuel storage systems and the pipes connecting them to combustion appliances shall be so constructed and separated from buildings and the boundary of the premises as to reduce to a reasonable level the risk of the fuel igniting in the event of fire in adjacent buildings or premises.

J6 Protection against pollution Oil storage tanks and the pipes connecting them to combustion appliances shall – • be so constructed and protected as to reduce to a

reasonable level the risk of the oil escaping and causing pollution; and

• have affixed in a prominent position a durable notice containing information on how to respond to an oil escape so as to reduce to a reasonable level the risk of pollution

Requirements J5 and J6 concern tanks, bottles and pipelines to store and deliver heating oil and LPG, where these are situated outside of the building. The associated guidance is to be found in Section 5 of ADJ. Its scope is effectively limited to systems of “domestic” scale, and larger systems are covered by legislation or codes issued by other authorities.

The guidance is chiefly aimed at: • preventing the ignition of the stored fuel through shielding vessels

from fires that may occur, installing fire valves in supply lines and ensuring the dispersal of LPG leaks; and

• controlling the risk of groundwater pollution from leaking oil.

These recommendations have minimal bearing on the building design although where tanks stand alongside buildings they can restrict the options for openings into the building envelope and affect the design of eaves.

Approved document K - Protection from falling, collision and impact

K1 Stairs, ladders and ramps

Stairs, ladders and ramps shall be so designed, constructed and installed as to be safe for people moving between different levels in or about the building.

ADK provides guidance on stair, ladder and ramp design that includes specifications for headroom, length of flights, landing areas and handrails.


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Explanatory note

K2 Protection from falling

(a) Any stairs, ramps, floors and balconies and any roof to which people have access, and (b) any light well, basement area or similar sunken area connected to a building,

shall be provided with barriers where it is necessary to protect people in or about the building from falling.

Guidance in ADK describes up-stands guarding the edges of floors, including edges below opening windows, with specifications for their height and strength.

K3 Vehicle barriers and loading bays (1) Vehicle ramps and any levels in a building to which vehicles have access, shall be provided with barriers where it is necessary to protect people in or about the building.

(2) Vehicle loading bays shall be constructed in such a way, or be provided with such features, as may be necessary to protect people in them from collision with vehicles.

ADK describes the use of vehicle barriers and approaches to safety in loading bays.

K4 Protection from collision with open windows etc. Provision shall be made to prevent people moving in or about the building from colliding with open windows, skylights or ventilators.

ADK offers alternative strategies for meeting the requirement: minimum headroom to the bottom of open windows; suitable barriers; or marking hazardous zones on floors.

K5 Protection against impact from and trapping by doors

(1) Provision shall be made to prevent any door or gate -

(a) which slides or opens upwards, from falling onto any person; and

(b) which is powered, from trapping any person.

(2) Provision shall be made for powered doors and gates to be opened in the event of a power failure. (3) Provision shall be made to ensure a clear view of the space on either side of a swing door or gate.

Requirement K5 (applies to sliding and powered doors, although lift doors are outside the scope of the requirement). The ADK guidance outlines technical measures to limit the movement of sliding and powered doors and recommends the use of vision panels in certain manual swing doors to allow occupants to see each other.

Approved Document L - Conservation of fuel and power L1 Dwellings This is the counterpart to Requirement L2, which is discussed below.

Neither the requirement is reproduced here nor is the corresponding Approved Document discussed as their subject matter is entirely concerned with the conservation of fuel and power in dwellings.

L2 Buildings or parts of buildings other than dwellings

Reasonable provision shall be made for the conservation of fuel and power in buildings or parts of buildings other than dwellings by – i) limiting the heat losses and gains through the

fabric of the building; ii) limiting the heat loss

a) from hot water pipes and hot air ducts used for space heating;

b) from hot water vessels and hot water service pipes

iii) providing space heating and hot water systems which are energy-efficient;

iv) limiting exposure to solar overheating; v) making provisions where air conditioning and

mechanical ventilation systems are installed, so that no more energy needs to be used than is reasonable in the circumstances;

vi) limiting the heat gains by chilled water and refrigerant vessels and pipes and air ducts that serve air conditioning systems;

vii) providing lighting systems that are energy-efficient;

Part L2 of the Building Regulations concerns the conservation of fuel and power in non-domestic buildings. There is a single requirement to conserve fuel and power by achieving sub-goals (a) to (h).

The Approved Document recognises three alternative techniques for complying with the requirement.

The first of these is the Elemental Method. In this, the building complies with Requirement L2 if each element of its envelope and each of its energy-consuming building services achieves its individual performance target. The method is conceptually the simplest but although there are some permitted trade-offs between certain performance targets, it offers the least flexibility in building design.

The other two methods are intended to allow more flexibility, but are more complex to apply. They are the Whole-Building Method and the Carbon Emissions Calculation Method. These two approaches can be adopted for the design of office buildings. Under each of these approaches, the building will meet the requirement if the operation of its heating, ventilation, air conditioning and lighting systems emits no more carbon per year than a specified benchmark.


21


Explanatory note

providing sufficient information with the relevant services so that the building can be operated and maintained in such a manner as to use no more energy than is reasonable in the circumstances.

The Elemental Method

Measures to comply with L2(a) are particularly likely to influence building design in ways that affect the building envelope. The measures should: limit the heat loss through the building envelope through the use of insulation; limit heat gains in summer; and minimise unnecessary air infiltration through the building fabric.

Compliance with L2(a) by the elemental method in effect demands that the heat loss through the building envelope does not exceed that which would have obtained if:

the building were constructed of building elements (walls, floors, roofs and roof lights, windows and doors etc.) having U-values no greater than those listed in the document; and

having window, door and roof light areas no greater than as specified; and

having no significant additional heat paths at the junctions and edges of the elements as a result of thermal bridges and gaps in the insulation (references are given for advice on detailing to achieve this).

Designers have some flexibility in how this performance target can be met using trade-offs between actual U-values for different elements and trade-offs with window areas. However, there are overriding maximum elemental U-values for wall and roof elements along with certain other constraints, including that daylight levels are adequate.

ADL2 provides extensive tables of U-values for all of the aforementioned elements, constructed and insulated in various ways. Where elements

such as walls and roofs have repeated thermal bridges, methods of calculating their U-values are identified and some example calculations given.

It is also possible to calculate an acceptable trade-off between the average U-value of the envelope and the efficiency of the heating system, provided that this does not effect the rate of carbon emissions. The document explains how this can be done.

The document offers advice to avoid solar overheating (except where calculation shows this not to be a problem in the particular case). The measures described include the specification of appropriate glazing, shading and limiting the area of glazing as a fraction of wall area – the maximum being dependent upon orientation. A method is provided for calculating the solar heat load per unit floor area under standard conditions and the document recommends that this should not exceed 25 W per m2. The calculation shows the dependency of the heat loading on the use of internal blinds and different types of glazing (e.g. low e; reflective; absorptive).

Concerning air infiltration through the envelope, the document sets a target average leakage rate of no more than 10m3 per hour per m2 (of total building envelope) at an internal overpressure of 50Pa. It offers only an outline of how the building can be built to achieve this although references are given for more detailed advice on particular building types.

Criteria for acceptable efficiency of heating plant are given and there is guidance on designing heating systems and their controls that make efficient use of energy.

Standards are given for insulating pipes, ducts and vessels.

ADL2 sets criteria for acceptable (building-averaged) efficiency in electric lighting and shows how this can be calculated for building types including offices. Advice is given on the provision of controls to enable the unnecessary use of artificial lighting to be minimised.

Criteria are given for the minimum acceptable efficiency of air conditioning systems or mechanical ventilation systems, if these are to be installed in office buildings. The criteria are given as a “Carbon Performance Rating” and the document provides the procedure for its calculation.


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Explanatory note

Whole-Building Method.

This method has been developed as the Whole-Office Carbon Performance Rating Method as described in BRE Digest No. 457. The building will meet the requirement if the combined carbon emissions of its building services do not exceed limits expressed as kg Carbon per m2 per year. The acceptance vary with building type and whether new or refurbished. Despite the greater flexibility, there remain some overriding maxima on envelope U-values and strictures to avoid unnecessary thermal bridges and gaps in insulation, as given for the Elemental method.

The Carbon Emissions Calculation Method

This is essentially similar to the Whole-Building method but the design should emit no more carbon than would a notional building of the same shape and size but designed to comply with the Elemental Method.

Work on existing buildings: It may be noted that the level of provision (for example the degree of insulation of walls) needed to meet Requirement L2 when working on existing buildings will depend upon the circumstances and may not be as described above.

Approved Document M - Access and facilities for disabled people

M1 Interpretation

In this Part "disabled people" means people who have - (a) an impairment which limits their ability to walk or which requires them to use a wheelchair for mobility, or (b) impaired hearing or sight.

M2 Access and use

Reasonable provision shall be made for disabled people to gain access to and to use the building.

M3Sanitary conveniences

(1) Reasonable provision shall be made in the entrance storey of a dwelling for sanitary conveniences, or where the entrance storey contains no habitable rooms, reasonable provision for sanitary conveniences shall be made in either the entrance storey or principal storey. (2) In this paragraph "entrance storey" means the storey which contains the principal entrance to the dwelling, and "principal storey" means the storey nearest to the entrance storey which contains a habitable room, or if there are two such storeys equally near, either such storey. (3) If sanitary conveniences are provided in any building which is not a dwelling, reasonable provision shall be made for disabled people.

M4 Audience or spectator seating

If the building contains audience or spectator seating, reasonable provision shall be made to accommodate disabled people.

Some of these requirements have a limited application to dwellings and within the supporting Approved Document ADM, the guidance is separated into that which does and that which does not apply to dwellings. The summary that follows is for non-domestic buildings.

ADM provides guidance on designing for adequate access to buildings and into them. It deals with aspects of pedestrian approaches, such as their ramps, steps and handrails and the need to ensure these routes are negotiable by those with impaired vision. There is guidance on the selection of types and sizes of doors and on lobby dimensions.

The issue of mobility within buildings is likewise addressed, with guidance on the design of doorways, including their size and on the use of vision panels. There are recommendations for internal lobby and corridor designs. There is guidance in connection with vertical circulation in buildings, in particular the provision and design of passenger lifts and stairs suitable for disabled use.

To facilitate the use of buildings, there are recommendations specific to the design of hotel bedrooms, changing rooms and washing facilities and so that catering facilities can be used without assistance. A particular recommendation in ADM is that there should be aids to communication in certain locations using, for example, loop-induction or infra-red transmission systems.

Sanitary arrangements are described, covering the design of facilities and their disposition within buildings. There is advice on what provisions for wheelchair users in theatres, sports stadia etc. would meet the requirements.

Approved Document N - Glazing – safety in relation to impact, opening and cleaning

N1 Protection against impact Glazing, with which people are likely to come into contact whilst moving in or about the building, shall – • if broken on impact, break in a way which is

unlikely to cause injury; or • resist impact without breaking; or • be shielded or protected from impact

The guidance describes locations (defined in terms of height relative to finished floor level in internal and external walls, partitions and doors) where glazing panels are regarded as posing their greatest risk. It recommends measures to reduce the risk in these circumstances by: • selecting glazing materials that break safely; or • using material that is inherently strong, or installing it in small panels;

or • physically guarding glazing, such as with grilles and appropriate specifications are given in each case.


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Explanatory note

N2 Manifestation of glazing

Transparent glazing, with which people are likely to come into contact while moving in or about the building, shall incorporate features which make it apparent

Manifestation, or marking, of glazing is required in critical areas where people moving in or around a building might not see an area of glazing and might collide with it. Examples of critical areas are fully glazed doors, and internal or external glazed walls. Manifestation can take the form of etched patterns or transfers applied to the glass at the normal sight level of those using the building.

N3 Safe opening and closing of windows etc.

Windows, skylights and ventilators which can be opened by people in or about the building shall be so constructed or equipped that they may be opened, closed or adjusted safely.

Provisions to ensure that controls for window opening can be safely reached and measures to prevent persons falling out of upper floor windows are described.

N4 Safe access for cleaning windows etc.

Provision shall be made for any windows, skylights or translucent walls, ceilings or roofs to be safely accessible for cleaning

Measures are described to give access to both sides of glazing for cleaning, where otherwise it could not safely be reached from the ground or other safe surface. Recommendations are to install windows of design (e.g. reversible) and size (criteria given) that enable all surfaces to be reached from within the building or provide various provisions to facilitate safe access from outside by ladders, walkways, cradles etc.

Approved Document for Regulation 7

Materials and workmanship

Building work shall be carried out - i) with adequate and proper materials which

a) are appropriate for the circumstances in which they are used;

b) are adequately mixed or prepared; and

c) which are applied, used or fixed so as adequately to perform the functions for which they are designed; and

in a workmanlike manner.

The main point of this AD is that compliance can be met by the use of proper materials of a suitable nature and quality in relation to their intended use. Workmanship should ensure that materials are adequately mixed or prepared, and applied, used or fixed so as to perform the intended functions.

The AD gives details of how to demonstrate the fitness of materials. There is also reference to the environmental impact of building work and suggests consideration of the use of recycled and recyclable materials – subject to such materials not having an adverse implication on the health and safety standards of the building work.

It refers to short-lived materials. The main issue here is that if materials that have a life shorter than the expected life of the whole building or building system are to be used they must be readily accessible for inspection, maintenance and replacement. This has an overriding proviso that the consequences of failure should not risk the health and safety of persons in and around the building. Materials that are likely to be affected by moisture can be used if they are protected from any likely damage from moisture and/or condensation. It notes that the performance some materials may be affected by certain environmental conditions. They can be used providing it can be shown that the residual properties are adequate for the intended function for the life of the building.

3.2 The Construction (Design and Management) (CDM) Regulations 1994

3.2.1 Aims of the regulations

The CDM Regulations are aimed at improving the overall management and co-ordination of the health, safety and welfare of those involved throughout all stages of a construction project to reduce the large number of serious and fatal accidents and cases of ill health which happen every year in the construction industry. It also aims at improving the health and safety of those who need to look after the building

The CDM Regulations apply to most construction projects and all demolition. However, there are a number of situations where the Regulations do not apply. These include:


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• construction work other than demolition that does not last longer than 30 days and does not involve more than four people,

• construction work for a domestic client, • construction work carried out inside offices and shops or similar premises without

interrupting the normal activities in the premises and without separating the construction activities from the other activities,

• the maintenance or removal of insulation on pipes, boilers or other parts of heating or water systems.

The CDM Regulations place duties on all those who can contribute to the health and safety of a construction project. Duties are placed upon clients, designers and contractors and the Regulations create a new duty holder; the planning supervisor. They also introduce new documents; health and safety plans and the health and safety file.

3.2.2 The role of the designer

Designers are organisations or individuals carrying out design work for a construction project, including temporary works design. Under the Regulation, the term designer includes architects, engineers, quantity surveyors, chartered surveyors, technicians, specifiers, principal contractors and specialist contractors. Design includes drawings, design details, specifications and bills of quantity.

Designers play a key role within the construction project in ensuring that the health and safety of those who are to construct, maintain or repair a structure or building are considered during the design process. They have to consider the potential effect of their designs on the health and safety of those carrying out the construction work and others affected by the work. This means there will be a need to assess the risks of the design which can reasonably be foreseen. In the main, this will include risks to those persons building, maintaining or repairing the structure as well as those who might be affected by this work.

To ensure that risks to health and safety are fully considered, a risk assessment should be carried out to:

• identify the significant health and safety hazards likely to be associated with the design and how it may be constructed and maintained,

• consider the risk from the hazards which arise as a result of the design being incorporated into the project.

The design should be altered to avoid the risk, or where this is not reasonably practicable, reduce it to an acceptable and manageable level.


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4. Office building design

4.1 Office construction technologies

4.1.1 Introduction

The design of office buildings is changing fast. Office buildings, once only seen as a symbol of corporate power and prestige, must now contain adaptable and flexible spaces to cope with the changing demands of the business that occupies it. The building must be capable of enhancing the process that it houses. Building owners and occupiers look for ‘long life, loose fit’ where the basic structure of the building is seen to last longer than those components that will require adjustments to suit the changing demands of different occupiers. The shell (ie, the structure and the core, including stairs, plant rooms, toilet areas, lift shafts and ducts) are rarely altered even during a complete refurbishment. The cladding, the internal partitions and services may be adapted, changed or disposed of a number of times over the life of the building. The list below summarises the length of time each element of a typical modern office building is expected to last:

• site (indefinite), • structure (60 years or more), • skin or envelope (30-60 years or more), • services (15-20 years), • space planning elements – e.g. partitions and associated services (5 years), • work settings (constantly changing).

4.1.2 Building plan depth

The optimum width of a building is often dictated by the distance that daylight can penetrate. A generally accepted rule of thumb for this is between 5 and 7m (or a floor to ceiling height multiplied by 2.0 to 2.5m).

Depths of 15 -18m are very common, and are suitable for use with a variety of mechanical systems, including conventional air conditioning, and mixed-mode natural and mechanical ventilation. Depths of less than 15m are preferred for effective natural ventilation, but very narrow plates (of 13.5m or less) do not efficiently accommodate a mixed cellular and open-plan working space, although this was popular in the 1950s and 1960’s. The maximum plan depth regarded as within the range of good practice in the UK is 21m.

The relationship between plan depth and building section has to be taken into account. Natural light and ventilation are easily available to occupiers of perimeter space by windows. Comfort in the space which is not within this perimeter zone has to be maintained using artificial light and ventilation, with resulting effects on energy consumption.


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Figure 1: Shallow floor plate 12 -15 metres

Figure 2: Medium depth floor plate 15-20 metres

Figure 3: Deep plan floor plate 20 + metres


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Figure 4: Structural and planning grids [Ref 1]

4.1.3 Structural and planning grids

The need to be able to readily reconfigure floor spaces is best accommodated by avoiding the use of permanent structural walls such as those commonly used internally in traditional domestic housing. This means using a system of structural columns and beams supporting floor slabs. These should be capable of carrying a live load of 2.5 kN/m2 over approx 95% of each potentially sub-lettable floor area, with a standard allowance for dead load for demountable partitions of 1.0 kN/m2 and 0.85 kN/m2 for raised floors, suspended ceilings and building services such as air conditioning equipment.

Historically, and in particular during the 1970s and 1980s, UK office buildings were designed with floor loadings significantly higher. Research has shown this to be an over-provision and most are now designed to the above standards.

The structural system is constructed from steel, reinforced concrete or a combination of the two. The floor is either reinforced concrete (poured on site (known as in-situ) or pre-cast), or a composite of in-situ reinforced concrete and corrugated steel acting as permanent shuttering over the whole floor plate.

The column grid dimension is a multiple of the planning grid dimension. The column grid should be as large as possible taking into account the characteristics of the proposed structural system and


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having regard to capital cost and floor-to-floor height constraints. In general, spans of 7.5m to 9m are considered to be economic.

The planning grid reflects the smallest unit of subdivision of space made available by a particular structural system. A horizontal/plan grid for the glazing mullions of 3.0m is often selected because cellular offices are rarely narrower, although a 1.5m planning grid will inevitably provide more layout flexibility.

The planning grid is typically expressed on the elevation to facilitate partitioning of perimeter offices, and it also operates as the co-ordinating grid in plans for the principal components of the structure including column grid, envelope, services, fabric and finishes, ceiling tile grid and partition grid.

4.1.4 Building cross-section

The overall dimensions for services and structural zones will depend on the frame solution and extent of services to be included. For column grids of up to 9m centres, it is usual to keep the horizontal services in a separate zone from the structure. For larger span spaces, a different strategy is needed to avoid large storey heights. The space between and sometimes through long-span beams is the main area of services distribution (see Figure 5).

Services/ceiling/lighting zone: 150-450mm overall. Included in the ceiling zone will be light fittings, air conditioning grilles in either metal or plastic, fire and smoke detectors and sprinklers if required.

Floor-to-ceiling height: 2600-3000mm. The choice of floor-to-ceiling height within these dimensions may be influenced by building plan depth, the form of ventilation system selected and daylighting.

Raised floor zone: 150mm overall. This dimension may increase by a further 300mm to 450mm if an under-floor air conditioning or ventilation system is adopted.

Specialised operations: If the building incorporates dealing operations, the slab-to-slab height will be increased on relevant floors to accommodate the requirement for greater raised floor and ceiling void depths of 200-300mm overall. Modern cabling, fibre optics and wireless technology have reduced the need for very deep floor voids in dealer areas.


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Figure 5: Vertical dimensions

4.1.5 Structural elements

4.1.5.1 Floor Slabs

Office floors in commercial purpose-designed office buildings are constructed using reinforced concrete, either cast/poured on site or pre-cast as planks. There are a number of variants designed to cope with different floor spans and construction speeds, and to reduce the amount of concrete. They all incorporate steel reinforcement which takes the form of main top and bottom reinforcement bars to cope with bending and shear strains. Some systems include a mesh of finer steel which takes the form of regular grid often 100 x 200mm. Mesh sizes can be 200 x 200mm, 100 x 200mm, or 100 x 400mm. The size of the reinforcement mesh sheets is standard at 4800 x 2400mm wide.

Floor slab zone 300mm

Services zone 150-450mm

Office zone 2600-3000mm

Raised floor zone 150-450mm

Beam zone

Sill zone 900mm


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A flooring system that has become common, particularly for steel structures, is the composite system. Permanent corrugated steel sheet is used as permanent shuttering for the in-situ concrete topping.

4.1.5.1.1 Concrete ribbed floor

Profiled concrete floor, which provides strength with minimum weight and volume of concrete.

Figure 6: Concrete ribbed floor

4.1.5.1.2 Hollow pot concrete floor

Hollow cored in situ or pre-cast reinforced concrete floor slab, again providing strength with minimum weight and volume of concrete, as shown in Figure 7.

4.1.5.1.3 Composite floor

This construction uses 1-2 mm gauge galvanised steel permanent formwork onto which a 100-200 mesh reinforced in-situ mesh reinforced concrete floor slab is cast, as shown in Figure 8.


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Figure 7: Hollow pot concrete floor

Figure 8: Composite concrete and steel floor


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4.1.5.2 Concrete columns

In situ or pre-cast reinforced concrete.

Figure 9: Concrete columns

4.1.5.3 Concrete Beams

In situ or pre-cast reinforced concrete.

Figure 10: Concrete beam

4.1.6 Roofing

Roofing may be flat or pitched. ‘Flat’ roofs are laid with falls ranging from about 10o down to 1.5o and pitched roofs start at 20o and can be as steep as 45o, although steep pitches are uncommon for wide spans as the roof ridge height becomes excessive.

4.1.6.1 Flat roofs

Flat roofs are covered with waterproof membranes consisting of either built up felt, (two or three layers of glass fibre or polyester based felt or a single ply polymeric membrane), or mastic asphalt. All systems are fully supported either on a deck of in situ or pre-cast concrete, a composite in situ concrete and steel system (see Figure 8) or on troughed metal. Falls can be provided for with cement


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based lightweight screeds on concrete, sometimes by tapered insulation panels or tapered firings on the beams or joists. Vapour control is important in avoiding interstitial condensation due to warm moist air rising from within the building and hitting a cold bridge within the roof void. Insulation can be provided under the roof covering or on top (known as an inverted system). In the case of the inverted roof, the waterproof layer is on the warm side of the insulation and acts as a vapour control barrier, avoiding the need for a separate membrane.

Figure 11: Flat roof - built up felt on concrete

Figure 12: Flat roof - built up felt on steel deck (see also Figure 19 below for composite deck)


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Figure 13: Flat roof – inverted

4.1.6.2 Pitched roofs

Pitched roofs are more common on low to medium rise office buildings than on high rise units (above 10 floors) where mainly flat roofs are adopted. Pitched roofing can use self supporting profiled metal such as galvanised steel, which may also be PVC coated, stainless steel or aluminium, or fully supported lead, zinc or copper. Fully supported roofs can also be laid flat, at around 10o, but are not common in new build.

Figure 14: Pitched roof - metal sandwich system


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Roofs on low rise office buildings of 4 floors or less, as shown in Figure 15 below, might be covered with slate, clay, concrete or fibre cement tiles.

Figure 15: Typical low rise office building (Ref AJPlus)

4.1.7 External cladding

4.1.7.1 Curtain walling

Curtain walling is a very common form of external cladding for office buildings. In essence, it a cladding system with glazing contained within or superimposed on a grid of slim framing members. It has no load bearing function other than to carry its own self-weight and to transmit the positive and negative wind loads it receives back to the primary structure behind. It may be applied to all faces or elevations of the building, although in the case of narrower, rectangular, floor plates, the end or flank


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facades may be clad with heavier construction such as masonry or concrete. These flanking elevations may not have any glazing except perhaps to stair towers. A typical example is shown in Figure 16. Details of a typical glass cladding section is shown in Figure 17.

Figure 16: Typical glass-clad building (Ref AJPlus)


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Figure 17: Typical curtain walling

Like other cladding systems, curtain walling can be prefabricated as panels off site or assembled on site from its component parts. Curtain walling can be made up from a number of different materials for the framing and for the infill panels. Framing is most commonly made from steel or aluminium. Steel was common in the early days of curtain walling in the late 1950s. Nowadays nearly all framing is in aluminium. Infill panels are mainly glass, but backed where appropriate at floor levels and back up walls to sill levels. In these situations, the glass may be coloured to render it opaque or be substituted with other sheet materials such as steel, aluminium or fibre reinforced board, often backed with or encapsulating insulation.

Since the 1970s, there has been a growth in the use of toughened glass supported by edge cleats to a backing framing system with the joints between the glass being sealed with a gasket or durable silicone sealant.

4.1.7.2 Other cladding systems

A range of alternative brick and concrete cladding systems is shown in the following figures.

The office in Figure 18 has an innovative wall construction; an external leaf of self-supporting brickwork and an inner leaf of cast in-situ concrete 'columnettes' (175 x 1115mm-wide piers) set between the window openings and which support the cast-in-situ concrete floor slabs.


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Figure 18: Energy efficient office building


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The office is designed to be energy-efficient: the walls have 115mm insulation-filled cavities and their thermal mass, together with that of the concrete floor slabs, helps to modify internal temperatures. The soffits of the floor slabs, which form the office ceilings, are cast with a series of semi-spherical coffers into which lighting and air-extract ducts are fitted. Services are carried in the 450mm raised-access floor.

The windows are double-glazed with an inner pane of low-emissivity glass; the windows above the louvre shades on east and west façades are fitted with clear solar-control glass. Opaque glass spandrel panels backed with dense concrete block work are set below the windows.

The deep raised computer floor provides supply air and extracts the air from the floor below. There is no suspended ceiling and the concrete is exposed to provide passive environmental control by the use of its exposed mass. The ‘columnettes’ fulfil a similar role.

Figure 19 shows a section through the external wall of a typical modern office building. The structure consists of steel columns and beams and a composite flooring system comprised of permanent steel formwork and in situ mesh reinforced concrete. The external wall is made up structural silicone clear double glazed units with a toughened outer pane and laminated inner pane with low E coating. The glazing is supported by a polyester powder coated frame. Polyester powder coated horizontal aluminium sunshades are placed at high level on each floor.

The particular elevation shown includes exposed structural steel columns and beams at floor and parapet levels running along the length of the elevation. Behind the steel beam is a panel of insulation in a metal panel. The office space is air-conditioned using the suspended ceiling as a supply and extract route for the air. There is also a raised computer floor that is comprised of metal trays containing chipboard.

The structure of the building in Figure 20 comprises a cast in situ concrete frame of columns and floor slabs supporting a steel and timber pitched roof. The brickwork walls are self-supporting and independent of the frame; they are tied to it for lateral restraint.

The main structure of the building is an in situ reinforced concrete frame supported on mass concrete pad foundations. A 300mm thick flat slab at first floor level is supported by circular columns in the centre of each wing and by rectangular columns around the perimeter which are built into the cavity wall to give a flush face without protrusions.

From ground to first-floor level, a series of 440mm-wide brick piers runs at 3m centres in front of the concrete columns; windows and glazed lower panels backed with block work are set between them. The piers support an exposed 150 x 90mm parallel flange channel and a continuous spandrel of brickwork, 1,750mm high, which in turn supports a horizontal band of opening windows on a 1,500mm grid. The block work inner leaf rests on the first-floor slab. There are insulated galvanised steel panels above and below the windows, running the length of the elevation. The building is naturally ventilated and heated by conventional radiators.


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Figure 19: External wall of a typical modern office building (Ref AJPlus)


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Figure 20: Building with cast concrete frame of columns and floor slabs (Ref AJPlus)


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The building shown in Figure 21 is constructed using pre-cast concrete structural panelling system internally along with pre-cast concrete beams and floors. The building is clad with decorative pre-cast concrete panels bolted to the inner units.

Figure 21: Building using pre-cast concrete structural panelling system (Ref AJPlus)


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The windows, which are not continuous, are triple glazed and can be opened for ventilation. The glazing system incorporates a retractable perforated aluminium louvre blind between the inner double glazed unit and the outer single glazed panel. The raised floors conceal services to the conventional radiators. There is metal tiled suspended acoustic ceiling to each floor.

Figure 22 illustrates a load bearing masonry construction. The external walls comprise 140mm internal load bearing block work, 100mm cavity filled with insulation and a 102mm outer skin of facing brickwork. The two skins of masonry are tied together with stainless steel wall ties bedded into the mortar joints. The in-situ or pre-cast reinforced concrete first and upper floors are supported off the inner block wall. There can be up to 5 upper floors, although 4 or less are more common with this form of construction.

The windows are in aluminium double-glazed with low E coating to the inner pane. The windows are not continuous and appear as holes punched into the brickwork. In this example they are approximately 1500mm square, with each individual window separated from its neighbour by 1500mm of load bearing masonry.

The use of a raised computer floor and mineral fibre suspended ceiling is common. In earlier buildings (1950’s to 1970’s), a raised floor was less common, and a pattern of metal floor trunking 300mm wide and 40-50mm deep was used instead

Figure 22: Load bearing masonry construction


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4.1.7.3 Cladding ratios

In order to determine to impact of the various building materials, it is useful to understand what percentage of a building is typically clad with glass and how much is clad using other materials.

The elevations of many office buildings generally feature horizontal bands of glazing separated by horizontal bands of cladding which may commonly be glass, metal, brickwork, stone or concrete etc. A small number of recent buildings have full height glazing from floor to ceiling, but these have not been considered.

Figure 23 shows a part elevation of a typical three-storey office building which will be repeated over each additional storey and probably along the length of the whole elevation of the building. As can be seen from the figure, there are a number of variable dimensions depending on whether there is a suspended ceiling and/or a raised floor and/or varying floor to ceiling heights which may alter the ratio of the areas of glazing to the solid cladding panels in front of the structure, ceiling drops and sill height walls. Scenarios have been considered for both a maximum storey height and a minimum storey height, with dimensions shown in Figure 24.

Taking the greatest overall bay height (4600mm) and the lowest overall height (3600mm) of the example, both scenarios provide a ratio of glass to solid panel of around 40:60.

This ratio will vary if other intermediate variations of glass/upper panel/lower panel are used. The variation illustrated in Table 4 takes the maximum storey height with a minimum glass area and maximum solid area as an example giving a ratio glass to solid of about 35:65. Generally speaking the maximum glass area is unlikely to exceed 40-45% because of heat losses start to become unmanageable above this limit.

Table 4: Ratio glass to solid

Reference Area of bay

Area of glass

Area of ‘solid’ panels

Area of columns

Total area of ‘solid’

Ratio glass : solid

Maximum storey height

27.6 m2 11.76 m2 15.0 m2 0.84 m2 15.84 m2 43:57

Minimum storey height

21.6 m2 9.52 m2 11.4 m2 0.68 m2 12.08 m2 44:56

Maximum storey height, minimum glass

27.6 m2 9.52 m2 18.08 m2 35:65


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Figure 23: Typical three story office building

Roof level

Ground floor

See detail




Raised floor zone150-450mm

Beam zone

Cill zone 900mm

6000mm

400mm

Column panel in glass or metal

/ brickwork / stone / concrete

Glazing zone

Cladding panel in glass or metal / brickwork / stone / concrete

1200

-150

0mm

70

0-10

00m

m

1700

-210

0mm


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Figure 24: Maximum and minimum storey heights


Services zone 150mm

Office zone 2600mm

Raised floor zone 150mm

Beam zone

Cill zone 900mm

6000mm

400mm



Glazing zone


1200

mm

70

0mm

17

00m

m

Minimum storey height 3600mm


Services zone 450mm

Office zone 3000mm

Raised floor zone 450mm

Beam zone

Cill zone 900mm

6000mm

400mm



Glazing zone


1500

mm

10

00m

m

2100

mm

Maximum storey height 4600mm


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4.1.8 Glass

Pilkington K Glass is a high quality clear float glass with a specially formulated, permanent, transparent Low E coating applied pyrolitically to one surface during glass manufacture. The coating allows the sun's energy to enter the building and when incorporated into insulating units, significantly reduces heat loss. It should only be used in insulating units with the coated surface facing the airspace. Low E coatings were introduced from the mid-1980s.

The effect of the coating is to reflect the long wavelength energy (generated by heating systems, lighting and building occupants) back into the building. However, the transparent coating still permits the transmission of short wavelength energy originating from the sun. This solar energy is absorbed by the internal surfaces of the building and re-radiated at the longer wavelengths, which are then reflected, by the coating, back into the building. Since the coating is applied during glass manufacture, the glass can be toughened or laminated in its coated form.

Double glazing units are normally made up of 6mm outer pane, 12mm space and 6mm inner pane. The gap may be filled with argon or krypton gas. Glass size is often dictated by structural dimensions (ie the gap between the raised floor and the ceiling for full height glazing or more often between the sill and the ceiling or structure above). The recommended floor to ceiling height is 2600-3000mm. This could give a full height glazing of 2600-3000mm. More common would be a range between 1700-2100mm, as was shown in Figure 5.

On many buildings the glazing would be continuous, interrupted by columns at 3000mm centres. Each structural bay will be subdivided by mullions into a planning grid of 1500mm to accept partitions. Buildings constructed with load bearing masonry or of pre-cast cladding panels incorporating windows, tend have smaller windows. The glass zone can vary between 60-70% of the curtain walling system for full height glazing (see Figure 19) and between 30-40% when a sill is taken into account (see Figure 20).

4.1.9 Insulation systems in external walls

4.1.9.1 External insulation

This description relates to proprietary (Ispotherm) external wall insulation system, employing mineral wool insulation, with a glass-fibre reinforcing mesh and render finishes. The system shown in Figure 25 is applied to the outside of external walls of masonry or dense concrete construction and is suitable for new or existing buildings. A metal trimming strip with a recessed water drip used as the base profile and a galvanized sheet steel corner strip incorporating PVC-U nosing used as reinforcement for external corners and edges.


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Figure 25: Proprietary external insulation

4.1.9.2 Cavity wall insulation

4.1.9.2.1 Partial fill BBA 93/2884

Rockwool High Performance Partial Fill Cavity Slab (Figure 26) consists of layers of bonded, water repellent rock wool formed into resilient slabs using a resin binder; the slabs are heat cured and cut to standard sizes. All slabs have a belt mark covering one face. The slabs are normally positioned with this face outermost and offer some protection from rain penetration.

Figure 26: Partial fill Cavity Slab insulation

4.1.9.2.2 Partial fill BBA 94/2992

Kingspan Thermawall TW50 (Figure 27) is a rigid urethane foam insulation board, manufactured without the use of CFCs, with a foil facing on both sides. The product is supplied in sizes of 1200mm wide by 450mm or 600mm high by 25 mm thick. Other intermediate thicknesses up to 50 mm are


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also available. Foiold facing is often specified to provide additional insulation values and to act a vapour check.

Figure 27: Partial fill insulation – foil faced

4.1.9.2.3 Full fill BBA 94/3079

Rockwool Cavity Wall Batts (Figure 28) consist of layers of bonded, water repellent treated rock wool formed into resilient batts using a resin binder. The batts are 900 mm, 1140 mm or 1200 mm wide, and 405 mm or 455 mm high in the thicknesses and for the cavity widths. The batts, which are built into the walls as construction proceeds, are intended to fill the cavity.

Figure 28: Full cavity insulation


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4.1.9.2.4 Blown cavity fill BBA 86/1779

Rockwool blown-in Cavity Wall Insulation (Figure 29) consists of rock wool fibres which are treated with a mineral oil water repellent during manufacture. The length of the fibres and degree of granulation are subject to regular quality control checks by the manufacturer.

Figure 29: Mineral fibre blown fill

4.1.9.2.5 Blown cavity fill - BBA 86/1720

RMC Polybead expanded polystyrene (Figure 30) is supplied with a binding agent. The binding agent is used to provide long-term stability to the insulant.

Figure 30: Blown polystyrene cavity fill


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4.1.10 Internal finishes

4.1.10.1 Walls

Emulsion paint or vinyl coated plasterboard walls are common. Internal walls are usually constructed of one or two layers of plasterboard on light gauge steel studs (Figure 31, Figure 32). These walls usually span between the raised floor, or the carpet or vinyl finish on a screed, and the suspended ceiling when being used to provide individual offices or other rooms. This is so they can be readily taken down or repositioned without affecting or damaging the ceiling or floor finish.

Where a more permanent wall is required, for example for fire separation, the wall system (either built of stud, block work or concrete) will span between structural floor and underside of the floor above.

Figure 31: Section through plasterboard partition

Figure 32: Plan of plasterboard partition


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4.1.10.2 Suspended Ceilings

Most office buildings require a suspended ceiling over the working areas. These perform a number of functions.

• Decorative: it hides the underside of the floor above, which may be rough cast concrete and services such as cable trunking or conduits, water services and drainage, metal air conditioning duct work.

• Acoustic: it reduces reverberation times and noise transfer. • Functional: it houses light fittings, and often air intake and extract grilles which are connected to

the duct work, smoke and fire detectors, sprinkler heads and return air plenums.

Figure 33: Typical suspended ceiling

Suspended ceilings are either plasterboard, mineral fibre or metal tiles that are easily demountable. Plasterboard may be foil backed. Metal tiles may be perforated and backed with a fibreglass quilt encapsulated in plastic to provide an acoustic performance. The suspended ceiling support system is either cable or light gauge steel angles fixed to the structure.

4.1.10.3 Raised Floors

A common feature in offices is the raised computer or access floor. Its purpose is to distribute power and IT and telephone cabling to the middle of the office away from perimeter trunking. Raised floors can also be used to duct supply or return air and conceal piped services and drainage. Such floors come in tile form and are commonly made up high-density chipboard set into steel trays. Floor finishes are usually carpet, linoleum or vinyl.

Floor panel size is generally 600 mm x 600 mm, with a panel thickness of 32 mm. The core is generally high-density chipboard and the casing, corrosion resistant steel.


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Figure 34: Typical raised floor detail

4.1.10.4 Core areas

Core areas of office buildings include stairs, lifts, service risers and toilets:

• Staircase area: Staircases in modern buildings are generally used for escape purposes rather than inter-floor communication. A functional and utilitarian standard of finish, such as painted plaster wall finishes, vinyl covered or painted concrete floors and painted metal handrails, is common. Stairs may be pre-cast or in-situ concrete, or steel, with a vinyl or non-slip finish. Stairwell walls need to be constructed to provide fire separation and a protected shaft. They could be constructed from concrete, especially when used to provide additional stability to a concrete frame, block work or plasterboard on light gauge metal stud supports. Inter-floor communication stairs will be to higher standard of finish, although the construction would be similar.

• Toilets: Ceramic tiles or vinyl sheet to floors and tiles to the walls with laminate cubicles and vanity units are common. The main walls can be block work or plasterboard on metal studs. Stud walls may incorporate mineral fibre quilt for acoustic reasons.


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• Lift and vertical service ducts: As with staircases, these need to be protected from fire and will be constructed from similar walling systems. Some vertical air supply shafts may include metal fire shutters at floor levels operated on a fusible link or during a fire alarm situation. Other service ducts containing cables, drainage and other pipe work may also need to be fire stopped at each floor. This can take the form of concrete or foam infill.

4.2 Building costs

Construction costs are heavily influenced by the location, number of stories and the extent of air conditioning. Some typical values are shown for properties in the South East of England in Table 5 below.

Table 5: Office construction costs (source: Building Magazine, February 2003)

Cost (£/m2 of gross internal floor area)

Low rise Medium rise High rise

South East England city - high quality speculative offices-air conditioned

£1,000-1,250 £1,100-1,350

City and West End - high quality speculative offices - air conditioned £1,400-2,000 £1,850-2,430

City and West End - high quality owner occupied offices (including owner’s fit-out costs) - air conditioned

£2,000-2,600 £2,450-3,050

The costs can be subdivided into different construction elements. Table 6 is an example of how these costs might be allocated for an air-conditioned medium rise office. Each of the elements includes labour, materials and plant costs and often a share of other “Preliminary cost” items. Preliminary costs might include supervision, site accommodation, light and power, insurances, water for the works, scaffolding, cranage and hoisting, and travel. Material costs will depend on the trade being considered.

An accurate ratio between labour and materials can only be considered on a case by case basis and built up from estimated or measured quantities, taking into account appropriate preliminary costs. Table 7 illustrates a typical breakdown of labour and materials for some common site based activities.


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Table 6: Construction cost elements

Substructure 10.50%

Frame 5.00% External Walls 12.00%

Upper Floors 5.00% Windows and External Doors 12.00%

Roof 3.00% Internal Walls and Partitions 4.00%

Superstructure

Stairs 2.00% Internal Doors 2.00%

Wall Finishes 2.00% Ceiling Finishes 3.50% Internal Finishes Floor Finishes 4.00%

Fittings 2.50%

Sanitary Appliances 1.00% Ventilating Systems 0.50%

Services Equipment 0.50% Electrical Installations 2.50%

Disposal Installations 2.00% Gas Installations 0.50%

Water Installations 2.50% Lift Installations 4.00%

Heat Source 4.00% Preliminaries 6.00%

Services

Space Heating and Air treatment 3.00%

Other installations, site works 6.00%

Totals 100.00%


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Table 7: Typical labour and materials breakdown

Material - Labour Cost BreakdownMats Sundries Materials Labour Total Mats % Labour %

Facing Bricks 2nd Hand Stocks 102 Thick, facework both sides 21.47 2.22 23.69 35.79 59.48 m2 40 60 215 Thick, facework both sides 43.30 5.19 48.49 52.28 100.77 m2 48 52

PC Sum £150 per 1000 102 Thick, facework both sides 9.29 2.22 11.51 30.72 42.23 m2 27 73 215 Thick, facework both sides 18.74 5.19 23.93 47.21 71.14 m2 34 66

PC Sum £350 per 1000 102 Thick, facework both sides 21.68 2.22 23.90 42.42 66.32 m2 36 64 215 Thick, facework both sides 43.73 5.19 48.92 53.83 102.75 m2 48 52

Aerated Blocks 4 N/mm2 75 Thick 5.94 0.69 6.63 10.99 17.62 m2 38 62 190 Thick 15.05 1.72 16.77 17.47 34.24 m2 49 51

Turbo 2.8 N/mm2 100 Thick 8.21 0.86 9.07 14.52 23.59 m2 38 62 215 Thick 17.65 2.15 19.80 18.46 38.26 m2 52 48

Hi Strength 7 N/mm2 100 Thick 9.95 0.86 10.81 14.52 25.33 m2 43 57 215 Thick 21.40 2.15 23.55 18.46 42.01 m2 56 44

Dense Blocks Hi Strength 7 N/mm2 100 Thick 7.92 0.86 8.78 21.00 29.78 m2 29 71 215 Thick 18.91 2.15 21.06 27.06 48.12 m2 44 56

Plaster Hardwall 11 mm + 2 mm 1.68 0.04 1.72 8.71 10.43 m2 16 84

Thistle Universal 13 mm 2.02 0.05 2.07 5.47 7.54 m2 27 73

Carlite Lightweight 11 mm + 2 mm 1.39 0.03 1.42 6.20 7.62 m2 19 81

Class B Finish 3 mm 0.44 0.01 0.45 3.92 4.37 m2 10 90

Plasterboard 5 mm Joints, fill & scrim 9.5 mm - to timber base 1.98 - 1.98 3.92 5.90 m2 34 66 9.5 mm - to masonry base 3.69 - 3.69 3.92 7.61 m2 48 52

3 mm Joints, filled 9.5 mm - to timber base 1.98 - 1.98 3.92 5.90 m2 34 66 12.5 mm - to timber base 2.27 - 2.27 4.65 6.92 m2 33 67 15 mm - to timber base 2.47 - 2.47 5.47 7.94 m2 31 69

2 layers, joints, fill & scrim 2 x 9.5 mm - to timber base 3.90 - 3.90 7.75 11.65 m2 33 67 2 x 12.5 mm - to timber base 4.48 - 4.48 9.30 13.78 m2 33 67

Metal Stud Partition 2.1 - 2.4m high x 75 mm Single board @ side (12.5 mm) 18.21 - 18.21 38.75 56.96 m 32 68

2.1 - 2.4m high x 100 mm Double board @ side (12.5 mm) 27.89 - 27.89 43.40 71.29 m 39 61 2.4 - 2.7m high x 100 mm Double board @ side (12.5 mm) 31.12 - 31.12 48.87 79.99 m 39 61 2.7 - 3 m high x 100 mm Double board @ side (12.5 mm) 34.35 - 34.35 54.25 88.60 m 39 61

Suspended Concrete Floor

A Formwork Timber 11.94 1.56 13.50 26.32 39.82 m2 34 66 Reinforcement A193 mesh, top sheet 1.52 0.09 1.61 1.41 3.02 m2 53 47 Reinforcement A193 mesh, lower sheet 1.52 0.09 1.61 1.41 3.02 m2 53 47 Concrete C30 (150 - 450 mm thick) 58.35 0.56 58.91 35.11 94.02 m2 63 37

Total 73.33 2.30 75.63 64.25 139.88 m2 54 46

B Formwork Hy Rib Permenant Shuttering 12.65 2.43 15.08 19.27 34.35 m2 44 56 Concrete C30, 150 mm thick 58.35 0.56 58.91 35.11 94.02 m2 63 37

Total 71.00 2.99 73.99 54.38 128.37 m2 58 42

4.3 Future trends

The current stock of all buildings in the UK is only being replaced at a rate of 1-5% per year. In the short to medium term, this is unlikely to change much because of the pressure to minimise the use of scarce resources and the increasing tax burden on the disposal of demolition material. The revolution in information technology at first meant that a number of earlier office buildings were unsuited to the installation of large amounts of new cabling and the additional cooling loads brought about by the


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computers and screens. Computers are now more energy efficient, giving off less heat, and cabling can be replaced with fibre optics and even wireless technology.

This means that buildings subject to demolition in the recent past can be refurbished and brought up to current insulation standards, proving the basic structure is sound. This now often entails a complete internal refit, replacing ceilings, adding shallow raised flooring, replacing and/or installing air conditioning and tackling any health and safety aspects. The existing external wall cladding and roofing will either be replaced, upgraded internally with additional insulation or over-clad with new system.

Hence, buildings that may have previously have only had a masonry type cladding with single glazing could now include a combination of metal and low E glass comparable to a brand new construction.

4.3.1 Trends in cladding facades

Facades needs to fulfil a number of functions and a drop in performance of any could have collateral impact on how well the building performs, how much energy is wasted and the comfort of the occupants.

Facades need to manipulate and control:

• the weather – wind, rain, snow, • excessive heat ingress and escape, • ventilation, • views in and out, • sound attenuation, • maximise daylight – but control glare, • provide security, • present an image.

Facades are becoming more sophisticated and complex and are beginning to incorporate ‘intelligent’ features that automatically react to changes in the weather and the needs of the occupants. Cladding systems can now include:

• photovoltaic cells to generate electricity, • heating coils to generate heat but which also can be fed with cool water from, say, boreholes to

reduce summertime overheating, • louvres that follow the sun path to reject glare and overheating but still maximise daylight, • opening widows that are motorised and automatically react to indoor air quality, enable night time

purging to remove odours and unwanted air pollution, and at the same time cool the building for the next day. Occupants using hand held signallers can also operate such windows,

• double skin systems which provide an extra façade outside the normal double glazed line. This can act as a fully sealed system or as a rain screen to take the brunt of the weather, and as a stack ventilation system to provide tempered ventilation, which is useful on tall buildings where high


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winds make natural ventilation difficult. Double skin systems have been used successfully as over-cladding on existing buildings, where there is a requirement to smarten the look of the building and improve the performance of the cladding. On new buildings it will allow the designer to make the cladding more glassy, although the outer layer may include other components such as photovoltaic cells, see Figure 35.

Facades of the future are likely to include more glass and less framing, but also more moving and fixed components such as metal louvres, photovoltaic cells and so on (see Figure 35).

Figure 35: Double facade of the future

However, concern about terrorism may swing opinion against such a transparent façade and future cladding systems may become more robust and better able to withstand explosions and missiles. In this case, greater use of steel plating or other blast resistant materials and more robust walls of reinforced concrete to sill levels may be seen, along with smaller windows.





Beam zone

Dou

ble

skin

zon

e

Photovoltaics or heat

Adjustable louvres

Access walkway

Intelligent glass


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4.3.2 New glasses

New glass is being developed all the time.

A recent innovation is self cleaning glass. Self-cleaning glass is an ordinary float glass with a special photocatalytic coating. It is made by chemically bonding and integrating a microscopically-thin surface layer to the exterior surface of clear glass. The integrated coating reacts to the sun’s ultraviolet rays to gradually and continuously break down organic dirt. This type of glass also has hydrophilic properties, which means that rain flows down the pane as a sheet, washing away the dirt instead of leaving the dirt behind as with normal glasses.

Electrochromic glass changes colour from clear to, say, blue as it is adjusted to control the amount of heat and light entering a room. The darkening of the glass avoids overheating and reduces glare and reflection on computer screens and removes the need for external shades. It works by passing a low voltage across microscopically thin coatings on the glass surface, activating a tungsten-bearing electro-chromic layer which changes colour.

Electrically heated glass is a laminated glass, incorporating almost invisible electrically-conductive wires. It comprises two or more sheets of glass interlaid with one or more films of polyvinyl butyral (PVB). This assembly combines comfort with safety, whilst preventing condensation. Electrically heated glass is suitable for any situation where there is high moisture content in the air and where the difference between the internal and external temperature may lead to condensation risk.

Anti-reflective glass is float glass with a multi-layer metal oxide and nitride coatings coating which reflects a very low % of light. It offers maximum transparency and optical clarity, allowing optimum viewing through the glass at all times. The clarity of vision makes anti-reflective glass suitable for all applications where glass should be transparent.

Low-emission glass (Low-E) is a clear glass with a microscopically-thin coating of metal oxide. This allows the sun's heat and light to pass trough the glass into the building. At the same time, it blocks heat from leaving the room, reducing heat loss considerably.

Alarm glass is a special laminated glass designed and manufactured for security purposes. The interlayer is embedded with a very thin wire and then sandwiched between two or more sheets of glass. The wire forms an electrical circuit which activates alarm when the glass is forced.

4.3.3 New construction materials and techniques

Designers and developers are still considering the impact of 9/11 on structural performance, means of escape and fire resistance. Some of the enhancements being considered include additional staircases, on-floor refuges and secure HVAC systems.

New materials are being developed and new uses are being found for the use of recycled material. Carbon fibre and polymer based reinforcement may one day replace steel reinforcement. Carbon matting has been used to strengthen floors during major refurbishment work.


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A report by CIRIA [Ref 1] notes that the search for quicker, easier construction procedures will create increased demand for components and systems that exploit lightweight and novel jointing technologies using polymers, adhesives, sealants and engineering plastics. Developments in more advanced materials including new methods for curing concrete or genetically modified timber may emerge as established industrial products in the longer term (20 years). Timber composite floors are being developed for refurbishment projects taking advantage of an existing timber floor that needs upgrading.

The report also notes that there may be a trend in shorter life buildings that are purpose built and dismantled at the end of their use, with components and materials being recycled or returned to original supplier. This will encourage standardisation and off-site prefabrication and a trend to lease building components such as lifts and air conditioning plant (already happening), and cladding.

Changes in IT and the growth of smaller companies may see the end of the need for large office complexes.

5. Properties of building materials

The properties of a wide variety of building materials have been determined, based on published data assembled into a database by the National Physical Laboratory (NPL), where available, and on measurements taken by NPL where such data could not be found.

Measurements have been undertaken using a waveguide-based measurement technique in the frequency range 750 –1150MHz. Lower frequency measurements were not made, due to the difficulty and cost of undertaking them.

The data is summarised below.

5.1 Timber products

Considerable data is available in the literature relating to timber products, which is summarised in Table 8 below. Additionally, a single sample of plywood was measured experimentally, as shown in Figure 36.

In summary, it can be seen that timber products have very widely differing dielectric properties which are largely related to the density of the material. They are also highly susceptible to moisture ingress, which can have a significant impact on the material properties.


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Table 8: NPL data on timber products

Material class Material εr tanδ Frequency (MHz) State

3.7 0.31 10 1% moisture OAK

8 0.75 10 15% moisture

1.65 0.0053 40 0% moisture Ponderosa Pine

2.99 0.24 40 15% moisture

Yellow Poplar 1.6 0.0032 300 0% moisture

2.8 0.25 10 1% moisture Sitka Spruce

6 0.66 10 15% moisture

2 0.04 2450 1% moisture

2.2 0.36 2450 10% moisture

WOOD

Western Hemlock

4.8 1.1 2450 15% moisture

2.9 0.078 50 0% moisture

3.4 0.094 50 4% moisture

4.4 0.11 50 8.3% moisture

5.2 0.12 50 11.3% moisture

Douglas Fir

6.4 0.13 50 17% moisture

3.1 0.071 50 0% moisture

3.6 0.083 50 3.5% moisture

4.6 0.1 50 8% moisture

5.6 0.12 50 11.6% moisture

White Oak

7.4 0.16 50 17% moisture

HARDBOARD (MDF)

Evans MDF 3.08 0.106 300

Douglas Fir 1.7 0.061 300 0% moisture

US, fibre face 2.91 0.109 300

US, phenolic 2.85 0.102 300

US, Novoply 2.87 0.099 300

Birch 2.16 0.067 300

PLYWOOD

Fir 2.25 0.074 300

1.7 0.022 100 Oven dry

4.3 0.12 100 30% moisture

7.4 0.14 100 60% moisture

.4Mg/m^3

16 0.16 100 100% moisture

2 0.029 100 Oven dry

5.9 0.17 100 30% moisture

11.9 0.22 100 60% moisture

.6Mg/m^3

23 0.24 100 100% moisture

2.3 0.036 100 Oven dry

7.6 0.23 100 30% moisture

16 0.29 100 60% moisture

.8Mg/m^3

27 0.32 100 100% moisture

1.0Mg/m^3 2.7 0.039 100 Oven dry

WOOD vs Density

1.2Mg/m^3 3 0.044 100 Oven dry


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Plywood

2.5

2.6

2.7

2.8

2.9

3

3.1

3.2

3.3

3.4

3.5

0.75 0.8 0.85 0.9 0.95 1 1.05 1.1 1.15

Frequency (GHz)

Die

lect

ric c

onst

ant

0.1

0.11

0.12

0.13

0.14

0.15

0.16

0.17

0.18

0.19

0.2

Tan

delta

Dielectric constantTanD

Figure 36: Measured dielectric properties of plywood

5.2 Glass

Considerable data is also available in the literature relating to glass products, some of which is summarised in Table 9 below. Additionally, the table shows some values measured by QinetiQ for toughened and standard float glass. Samples of float, toughened and K-glass, which has a thermal film on one surface, have also been measured experimentally by NPL. The results for float and toughened glasses are shown in Figure 37. K-glass was found to be almost completely reflective at the frequencies of interest.

Table 9: NPL data on glass products

Material εr tanδ Frequency (MHz)

Corning - 7980 3.84 0.00004 2030

Corning - 7056 5.23 0.0049 1000

Corning - 7052 4.97 0.0046 1000

Corning - 7971 4 0.00014 4000

QinetiQ data

Standard Float glass 7.01 0.017 Not specified

Toughened glass 6.912 0.018 Not specified


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3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

0.75 0.8 0.85 0.9 0.95 1 1.05 1.1 1.15Frequency (GHz)

Die

lect

ric c

onst

ant

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

Tan

delta

Dielectric constant (Plate)

Dielectric constant (Toughened)

TanD (plate)

TanD (Toughened)

Figure 37: Measured dielectric properties of glass

Glass is, in general, highly consistent and the grades used in building construction largely impervious to moisture ingress. The properties are, however, highly variable, depending on the materials used to make the glass.

5.3 Building materials

Only limited published data was found relating to building materials. This is summarised in Table 10 below. Samples of thermolite block, standard house brick (Double Diamond), concrete, mortar, Rockwool insulation and plasterboard have been measured by NPL and the data is shown in Figure 38 to Figure 43 below. In general, the results show wide variations for similar materials, generally high levels of dielectric constant and losses and a great susceptibility to moisture ingress.

5.4 Summary

Table 11 summarises the dielectric measurement data. The most significant feature of the data is that many building materials are highly sensitive to moisture, ever-presence on external surfaces, and that their precise construction has a major impact on the dielectric parameters. This makes the design of a ubiquitous FSS structure to cater for a particular feature (for example, a cavity wall) a significant challenge.


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Table 10: NPL data on building materials

Material εr tanδ Frequency (MHz)

Comments

Portland cement / water 50/50 25.5 0.5910 500 After 140 hrs

Blast furnace cement / water 50/50 35.1 0.3914 500 After 140 hrs

"Young" concrete - Mix 1:

Cement 375kg/m3, Sand 787kg/m3, Gravel 1044kg/m3, Water / cement 45/55

21 1.0705 20 After curing

"Young" concrete - Mix 2 : Cement 320kg/m3, Sand 787kg/m3, Gravel 1044kg/m3, Water / cement 60/40

25.5 1.2342 20 After curing

California pavement - wet 13 0.4900

California pavement - dry 6.57 0.0530

2.32 0.0090 100 Ambient Gypsum Plasterboard

1.77 0.0060 100 Dried

Thermolite block

3

3.1

3.2

3.3

3.4

3.5

3.6

3.7

3.8

3.9

4

0.75 0.8 0.85 0.9 0.95 1 1.05 1.1 1.15

Frequency (GHz)

Die

lect

ric c

onst

ant

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

Tan

delta

Dielectric constantTan delta

Figure 38: Measured dielectric properties of thermolite block


65

3

3.5

4

4.5

5

5.5

6

6.5

0.75 0.8 0.85 0.9 0.95 1 1.05 1.1 1.15Frequency (GHz)

Die

lect

ric c

onst

ant

0.4

0.45

0.5

0.55

0.6

0.65

0.7

Tan

delta

Dielectric constant (dry)

Dielectric constant (wet)

TanD (dry)

TanD (wet)

Figure 39: Measured dielectric properties of mortar

2

2.2

2.4

2.6

2.8

3

3.2

3.4

3.6

3.8

4

0.75 0.8 0.85 0.9 0.95 1 1.05 1.1 1.15Frequency (GHz)

Die

lect

ric c

onst

ant

0.2

0.22

0.24

0.26

0.28

0.3

0.32

0.34

0.36

0.38

Tan

delta



TanD (dry)

TanD (wet)

Figure 40: Measured dielectric properties of concrete


66

4

4.5

5

5.5

6

6.5

0.75 0.8 0.85 0.9 0.95 1 1.05 1.1 1.15Frequency (GHz)

Die

lect

ric c

onst

ant

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

Tan

delta



TanD (dry)

TanD (wet)

Figure 41: Measured dielectric properties of domestic brick

1.016

1.017

1.018

1.019

1.02

1.021

1.022

1.023

1.024

1.025

1.026

0.75 0.8 0.85 0.9 0.95 1 1.05 1.1 1.15

Frequency (GHz)

Die

lect

ric c

onst

ant

0

0.01

0.02

Tan

delta

Dielectric constantTan delta

Figure 42: Measured dielectric properties of Rockwool insulation


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2.2

2.22

2.24

2.26

2.28

2.3

2.32

2.34

2.36

2.38

2.4

0.75 0.8 0.85 0.9 0.95 1 1.05 1.1 1.15

Frequency (GHz)

Die

lect

ric c

onst

ant

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

0.09

0.1

Tan

delta

Dielectric constantTanD

Figure 43: Measured dielectric properties of plasterboard

Table 11: Summary of dielectric data

Range of εr Material class

Dry material variation

Moisture susceptibility

Frequency sensitivity

Comments

Timber products 1-4 High εr up to 30

Believed to be low εr depends on density

Glass 3.5 – 7 None Believed to be low εr depends on type, K-glass completely reflective

Brick 3.5 – 5.5 Medium Believed to be low εr depends on type and moisture content

Thermolite block 3-4 High Believed to be low εr depends on type and moisture content

Concrete 3-30 High High εr depends on mix, age and dryness

Mortar 3-30 High High εr depends on mix, age and dryness

Plasterboard 1.5-2.5 Believed to be high Believed to be low εr depends on dryness

Rockwool 1-1.1 Likely to be high Believed to be low εr depends on dryness


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6. Conclusions

A large amount of metal in the form of steel and or aluminium is used in office buildings. Any generic reference case building model will need to assume the presence of metal in any or all the following locations (see Figure 47).

6.1 External wall cladding

Metal panels can form part of the cladding system between windowsill level and the window head of the floor above (spandrel panels) (see Figure 47). They may also be used between individual windows and as cladding to structural columns. Curtain walling can be to all elevations, although is more commonly restricted to the long elevations (Figure 44 to Figure 46)

Even though the spandrel panels may be constructed from alternatives such as masonry or pre-cast concrete panels (reinforced with steel), insulation may also be applied to the inside of external walls either within a cavity or as panels on the innermost skin. This may be backed, faced or fully encapsulated in steel sandwich panels or with aluminium foil.

The inner pane of modern double-glazing units is normally coated with a low emissivity metallic finish.

Figure 44: Extent of curtain walling on shallow floor plate 12 -15 metres

Curtain walling

Curtain walling

Masonry flank/end walls


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Figure 45: Extent of curtain walling for medium depth floor plate 15-20 metres

Figure 46: Extent of curtain walling for deep plan floor plate 20 + metres

Curtain walling

Curtain walling

Masonry flank/end walls

Curtain walling

Curtain walling

Cur

tain

wal

ling

Cur

tain

wal

ling


70

6.2 Structure

The structural frame of office buildings is either steel or concrete reinforced with steel. Floor slabs are reinforced concrete or a composite of corrugated sheet steel topped with lightly reinforced concrete.

6.3 Ceilings

Many offices have suspended ceilings to provide a flat surface (soffit) for partitions and to hide rough concrete finishes and exposed services. These may be constructed from panels of plasterboard or mineral fibre, sometimes backed by foil, or steel or aluminium. Ceiling voids will often contain steel ducts supplying and extracting air and carrying electrical services.

6.4 Floors

Raised computer floors are usually constructed of 600mm square metal pans containing a floor finish.

6.5 Internal walls

Most walls are designed to be easily taken down and reconfigured or disposed of at regular intervals, often on a 5-year cycle, to cope with changes in the organisation occupying the building. These are constructed of light gauge steel studding faced with one or two layers of plasterboard. The more permanent structural and vertical ducts, including lift shaft walls may be built of reinforced concrete.


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Figure 47: Potential Locations of sheet metal in office structures

7. Acknowledgements

A number of the figures in this section are based on information from the Architects Journal, the RIBA Product Selector, British Board of Agrement and BCO Best practice in the specification for Offices.

8. References

[Ref 1] BCO Guide Best practice in the specification for offices (British Council for Offices 2000) [Ref 2] UK Construction 2010 – future trends and issues Construction Industry Research and

Information Association (CIRIA) Report/CP/6 5 August 1999





Beam zone

Possible presence of sheet metal

Cill zone 900mm