residential concrete
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d e t a i l i n g a n d s p e c i f i c a t i o n g u i d er e s i d e n t i a l c o n c r e t e
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preface
This technical manual is published by theCement & Concrete Association of NewZealand with funding assistance from theNew Zealand Concrete MasonryAssociation.
The construction details containedwithin this manual have been developedbased on extensive research both locallyand internationally. They are designed togive examples representative of goodpractice, rather than a complete range ofpossible alternatives.
The manual is written by Morten Gjerde,Lecturer and CCANZ Fellow at VictoriaUniversity of Wellington, School ofArchitecture.
Heartfelt thanks to the following people,without whose assistance this would nothave been possible:
3
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* An additional coat of X-200 may be required on concreteblock due to regional variations in standards.
Research assistance:Rachel ChanPeter LoughOliver MarkhamNancy BakkerGrant Taylor
Peer review:Daniel BagustPhilip BlairRoss CatoJohn GibbonsDerek LawleyNigel MarshallAndy Wilton
Typing:Tricia Hawkins
Editing:Grant ThomasDene Cook
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5contents
General Information . . . . . . . . . . . . .7
Concrete Masonry . . . . . . . . . . . . . . .13
Insulating Concrete Formwork . . . . . .35
Precast Concrete . . . . . . . . . . . . . . . .55
Concrete Cast In-Situ . . . . . . . . . . . .77
References . . . . . . . . . . . . . . . . . . . .95
ISBN 0-908956-12-6
TM36
Cement & Concrete Association of New Zealand
Level 6, 142 Featherston St, Wellington.
P O Box 448, Wellington.
Tel: (04) 499 8820, Fax: (04) 499 7760. Email: [email protected]
Cement & Concrete Association of New Zealand 2000
Except where the Copyright Act allows, no part of this publication may be reproduced,
stored in any retrieval system in any form, or transmitted by any means, without the prior
permission in writing of the Cement & Concrete Association of New Zealand.
The information provided in this manual has been prepared with all due care; however the
Cement & Concrete Association of New Zealand accepts no liability arising from its use.
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residential concrete detail ing and specif ication guide
6
Mann House in Auckland by Ian Juriss.
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General Information
7
General Information
Concrete is well known to manyNew Zealanders as a building material.Being a country of doers has meant thatnot only are we familiar with concrete butalso many have had personal experiencewith it. Footpaths, garden walls, garagesand sculptures stand as testament to thishands-on experience.
In the construction industry, concrete isthe most widely used material both hereand overseas. Commercial structuresfrom single to multi-storey continue to bebuilt in concrete. Most residentialconstruction is based on the concreteground floor slab and our infrastructure,from underground pipes to bridges, islargely constructed of the material.
The building industry in New Zealand iswell resourced to construct in concrete.Raw materials are readily availablethroughout the country. The techniquesfor constructing formwork, placingconcrete, erecting precast elements andbuilding in masonry are to a very highstandard internationally. The design ofconcrete structures by local engineers leadthe world in many areas. The existence ofseveral quality suppliers of precaststructural systems and other proprietaryelements in the marketplace allowdesigners and builders competitivepricing, extensive system choice andexcellent technical support.
For all that, New Zealanders continue tofavour timber framing for theconstruction of their houses. It is notunusual to see a design modelled on themassive homes of the Mediterranean,built using spaced timber studs with athin cladding of stucco or acrylic plasteron rigid board. Many designers andhomeowners in this country prefer tocontinue to use systems and techniqueswith which they are familiar.
Concrete construction has been widelyused for housing throughout Europe andto a lesser extent in the United States. Itwould be difficult to think of the work by
Le Corbusier, Adolf Loos and morerecently Herzog and deMuron withoutconjuring up images of concrete. Marketresearch has been carried out in an effortto identify why concrete is not used morereadily in the residential constructionsector in New Zealand. These resultsindicates that there is inadequateinformation for those wanting to designand build concrete houses. There is also alack of builders who are comfortablebuilding concrete walls and suspendedfloors in the domestic context. Theprocesses involved in building in concreteare different to those employed in timberframing and cladding. Builderscomfortable with concrete have tended tobecome established in commercialconstruction. While the research pointedto an enthusiasm for concrete homes,designers and builders tend to stay withfamiliar materials and processes.
This publication seeks to bridge theknowledge gap for designers and buildersof concrete homes. It does not howeverclaim to fulfil all their information needs.It has been structured to give an overviewof the principles and highlight the criticalissues facing designers and builders. Theconstruction industry has been widelyconsulted and research has been carriedout both locally and internationally. Thedetails have been prepared to present abroad range of construction scenarios.The designer or the builder using thismanual may find the need to changerelationships or sizes shown to suit theirown purposes. The intention has been topresent a starting point from whichspecific details can be developed. Thedetails shown here have been checked forsuitability for New Zealand conditions.Provided the detailing principles areadhered to, others should perform equallywell.
introduction
The raw materials for concreteare readily available.
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residential concrete detail ing and specif ication guide
8
scope
This document has been prepared as a general guide to thedesign and construction of the single family house and projectsof similar scale in New Zealand.
Although this manual does not specifically address fire resistanceand sound transmission ratings, the adjacent table demonstratesthe values that can be achieved with appropriate detailing.
It presents materials and systems that are commonly available inNew Zealand. Some, such as timber joinery and concrete itself,have been in use for several generations. Others have recentlycome into the local market and industry experience with some ofthese may be limited. On the other hand, building products notavailable in New Zealand have not been incorporated. To do sowould inaccurately present the range of materials available here.
The construction, specification and detailing issues are presentedin the New Zealand context. We have specific and often uniqueways of doing things. The New Zealand environmentalconditions are also unique.
This book is principally concerned with design and constructionissues. While it does touch upon topics such as thermalperformance and structural engineering, it is not meant to serveas a guide in these areas. Structural design is still best left to theprofessionals except in those areas where non-specific designstandards are available. Concrete masonry is one such formatwith NZS 4229 having been revised in 1999.
The Cement & Concrete Association of New Zealand produces arange of other publications that may be of interest to thedesigners and builders of concrete homes. Further information isavailable at www.cca.org.nz.
Typical fire and sound transmission ratings that can be achievedwith concrete systems when appropriately detailed.
SILL DETAIL
Paving level
Butyl rubber sillflashing
Reinforced conc.slab
Recessed timber door& sill
Floor coverings
Non structural conc.veneer
Insulation
Structural conc. panelPanel Thickness Fire Rating Sound Transmission
Class (STC) rating
100 mm 90 minutes 44
120 mm 120 minutes 48
150 mm 180 minutes 55
200 mm >240 minutes 58
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9Objectives
Successful architectural detailing requiresattention to many factors. As with mostaspects of building, it is often necessaryto think laterally to achieve results thatare both poetic and satisfy pragmaticgoals.
First off, it is important to be able toclearly identify the detailing objectives.These may come under headings such as:
cost
appearance and aesthetics
buildability
materials usage
routine maintenance
All successful design and detailing effortswill consider these factors. The designermay make value judgments through theprocess, placing the importance of oneaspect above another. The critical thing isto be aware of these considerations andto understand the consequences offavouring any one over the other.
Environment
It is also important to consider thespecific environment that the details areto exist in. It is critical to acknowledgeand design for:
prevailing winds and wind patternscreated by the landscape or otherbuildings
rain and other weather that can beexpected
UV exposure
dust and pollutants that may be inthe air and settle on the building
corrosive elements in the air such assalt spray
moisture, either rising from theground, or as general humidity
Specific environments can vary from siteto site and even on different faces of thesame building. While exposed concretemasonry may be appropriate on thesunny north face of a house, its use onthe south side of a damp site could
quickly see mould and other organicgrowth develop, even with regularcleaning. If inappropriate materials areused or poor detailing choices are made,the building appearance can deterioratequickly.
Material properties
Concrete has a number of special andunique qualities that make it an idealconstruction medium, particularly indomestic applications. These include:
high durability
thermal mass benefits when usedappropriately
ability to form and shape
enclosure of space and structure inone material
ability to form integral surfacefinishes and colour
relatively inert and compatible withmost other buildings materials
excellent acoustic and fire resistantproperties
Along with these qualities are someinherent limitations that the designershould bear in mind:
detailing considerations
Frank Lloyd Wright was aninnovator with concrete.
Grigg House by Miles Warren.
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residential concrete detail ing and specif ication guide
10
once cast it is difficult to change
not sufficiently waterproof on its own
sharp corners or edges can bevulnerable to mechanical damage
Once the decision to use a concretestructure in residential projects is made,the designer and the builder must findways of optimising the positive attributeswhile minimising the negative aspects ofconcrete. The best way of ensuring this isthrough adequate and consideredplanning. This Guide is one resource tohelp with this planning.
Maintenance
Planning for routine maintenance of thebuilding, and in particular of the details,must be borne in mind. All materials anddetails perform better when they aremaintained. Such maintenance mayinclude washing, replacement of seals andsealants and re-application ofwaterproofing coatings.
Decisions made by the builder ordesigner may place high demands on thehomeowner to maintain certain details.Often the homeowner is not consulted orconsidered at the time, a point that isparticularly true of homes builtspeculatively.
Homeowners, where appropriate, shouldbe consulted with over maintenanceissues. In all cases, they should be madeaware of routine maintenancerequirements. The lifetime success of theproject will benefit.
An example of exposedaggregate finish.
Sargent House in Auckland by Ron Sang
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General Information
11
moisture control
Concrete, although used in the construction of water tanks, isnot generally considered to be sufficiently waterproof forhousing without supplementary waterproofing systems. Not onlyis concrete water permeable, it also contains excess water fromthe construction process that must be allowed to escape. Thismoisture can, if not dealt with, continue to plague thehomeowner. As a rule of thumb concrete requires one monthper 25 mm of thickness to dry (from each exposed face)assuming dry conditions. This means that under ideal conditionsa 100 mm thick concrete wall will require two months dryingtime if both faces are left exposed for that period.
Finishes that are applied to exterior surfaces of concrete whichhave not dried adequately, may be affected by the tendency ofwater to escape to the warm side. This could lead to bubbling ofthe surface finish.
The external moisture clauses of the New Zealand Building Codeare increasingly being complied with through the use of paintedmembrane systems. These systems are continuing to develop andthere are a number that have proven records in New Zealandconditions. Their use has increased the options for designers butat the same time designers must ensure that sound detailing andbuilding principles are not ignored.
If a strategy of reliance on painted membrane systems has beenadopted, it is advisable to thoroughly investigate the systemsunder consideration. Speak to those who have applied theproducts and have experience of their performance. Also obtaintest results and manufacturers guarantees of performance.
Internal moisture control is often not considered by designersbut is critical to the comfort and enjoyment of the home. Thebest method of assuring that the concrete home performs well inthis regard is to insulate well and to specify appropriate finishesin those rooms where high moisture levels can be anticipated.
The enjoyment of a well designed concrete home will beenhanced by the designer considering the environment, materialproperties and sound detailing principles.
thermal performance and insultationThermal mass within the building envelope can providesignificant benefits in terms of both energy efficiency andcomfort.
Maximising the thermal mass benefits of concrete requiresconsideration of a number of issues including: site and buildinglocation and orientation, insulation placement, glazingplacement and orientation, and usage patterns, to mention a few.
This manual does not attempt to cover issues which need to beconsidered in maximising the benefits of thermal mass.
Designers wishing to check thermal properties of concretehomes for code compliance should refer to two New Zealandstandards: NZS 4214 provides the means of calculating thethermal resistance of building elements, and NZS 4218 definesminimum requirements for the various elements of a house (iewalls, roof, floor).
This house will be left unpainted until allconstruction moisture has escaped.
A contemporary concrete house.
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Concrete Masonry
13
Concrete Masonry
General . . . . . . . . . . . . . . . . . . .15
Design Issues . . . . . . . . . . . . . .16
Specification . . . . . . . . . . . . . .19
Construction . . . . . . . . . . . . . . .21
Details . . . . . . . . . . . . . . . . . . .22
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Concrete Masonry
15
Concrete masonry or blockwork has a long association with residentialconstruction in New Zealand. Aswell as offering all the positive attributesof the other forms of concrete it is aneasy format to use.
The use of concrete masonry has beenwell supported by the blockmanufacturers throughout the country.Special profiles are available to suit all thedetailing conditions that can beanticipated. The range of productscontinues to be expanded as blocks withspecial surface finishes, sizes and thermalcharacteristics are put to the market.
In effect concrete masonry is a type ofpermanent formwork for concrete. Thegrout fill working in conjunction with thereinforcing steel provides the structuralstrength. New research carried out byNew Zealand universities has lead to areduction in the amount of horizontalreinforcing steel and grout fill required.140 mm wide (15 Series) concretemasonry has also been shown to bestructurally appropriate for mostresidential projects. These changes havebeen incorporated into the recentlyreleased update of NZS 4229:1999, theStandard for non-specific concretemasonry design.
Advantages of concrete masonry
economy particularly when theconstruction module is fully exploited
does not require special or costlyequipment to install
modular units are relatively easy tohandle and can be delivered to mostbuildings sites
stop and start of construction is easyto incorporate structurally andarchitecturally
range of profiles allowing for mostdetailing requirements
interesting architectural scale andsurface textures
The qualities and advantages of concretemasonry certainly make it an appealingmaterial to consider for residentialconstruction.
Until the nineteen -seventies NewZealand houses built of blockwork usedcavity wall construction techniques.Concrete masonry is more porous thanmost other forms of concrete. The blocksthemselves are permeable, particularlywhen they are manufactured using thelightweight pumice aggregate typical ofthe upper half of the North Island. It ishowever the mortar joints which are thereal culprit. As the mortar dries andshrinks, cracks develop against adjoiningblocks. Traditional cavity wallconstruction assumes moisture will beable to penetrate the outer skin, but thendrop to the bottom of the cavity and outthrough weep holes without affecting theinner skin. The outer skin of the wall alsoserves to conceal the waterproofingmembrane on the outer surface of theinner skin.
Time pressures and increases in the costof construction have meant that thiseffective traditional method ofconstruction has generally been replacedby the single skin masonry wall. As hasbeen discussed earlier in this guide thechange has been justified through thedevelopment of new materials whicheffectively seal the external surfaces whilealso serving as paint or plaster finishes.This is often in conjunction with rigidinsulation. NZS 4229: 1999 has adoptedthe use of acrylic membranes asappropriate waterproofing solutions.
Broderick House by Warren & Mahoney
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residential concrete detail ing and specif ication guide
16
design issues
Modular setout
While other forms of concrete construction allow freedom ofshape and size, the modular nature of blockwork directs manydesign considerations. For reasons of economy and ease ofconstruction, the modular height of units typically 100 mm or200 mm should be adhered to. This applies to overall heightsof walls as well as openings within walls. Sticking to a runningmodule of 200 mm will provide economy, however, the length ofunits can be easily cut. If the module is seen, the designer maywish to specify the position of the cut units.
Joints
The mortar joint between blocks has a number of functions. Itsprimary function is to bond adjoining blocks together. This is apermanent requirement for those blocks that are not to havefilled cores. The grout fill will otherwise take over as the bondingmechanism. Another function of the joint is to take upconstruction or manufacturing tolerances as slight variations inblock sizes may occur. Finally the joint contributes significantlyto the appearance of the concrete masonry wall. The industrynorm of a 10 mm joint is generally considered to be a goodproportion when compared to the individual masonry unit. Thiswidth can be varied by the designer to suit particularrequirements. When blockwork is designed to be left exposed,the colour of the joint is a consideration. It is, however, theprofile which offers the designer the greatest number ofvariations to suit aesthetic or weathering requirements.
Profiles of typical joints that can be specified are shown in theillustration to the left. Combining joint profiles, such asalternating flush with struck to suggest a different module, orraked horizontals and flush vertical joints can be effective.
Bonding patterns
The way in which the concrete blocks are laid presents anotheropportunity to affect the overall appearance of a wall. Thetraditional bonding pattern for concrete masonry is the ashlar orrunning bond. Another option is the stacked bond. Beyond these
raked flush
struck weathered
concavevee
Common mortar joint profiles
Stacked bondRunning bond
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Concrete Masonry
17
it is over to the designers imagination to consider the surfacepatterns and textures that can be achieved. Mario Botta, a Swissarchitect, is renowned for combining blocks of various colour,texture, height and laying position to create wonderful patternsthat become an integral part of his architecture.
Note that the bracing values for partial filled concrete masonryin NZS 4229 are based on the running bond. Partially filling astacked bond wall at 800 mm centres will leave every secondblock unbound which then becomes vulnerable underearthquake loading. It is therefore recommended to fill cells at400 mm centres or closer when using stack bonded concretemasonry.
Non-structural applications
Concrete masonry is generally used in a structural capacity, forwhich it is ideally suited. It can also be used as an external veneercladding in conjunction with other structural systems. The mostcommon is timber framing but combining structural and veneermasonry with a cavity between will allow the designer to takefull advantage of the external appearance, durability and thermalmass benefits.
Method of insulation
Appearance requirements and thermal mass objectives must beconsidered at the same time as the insulation strategies.
The most common method of insulating a concrete masonrywall is to strap and line the internal face, fitting insulationbetween the strapping. An alternative approach is to fixinsulation externally either in the form of rigid polystyrene sheetfixed in place with an external coating or by strapping andcladding with insulation between.
Proprietary self-insulating concrete block systems are available inNew Zealand. Such systems allow both faces of the concretemasonry. This is achieved through the use of a biscuit ofpolystyrene fixed in a cavity near the exterior surface of the block.
Concrete masonry built using the cavity method allows foreffective use of insulation, thermal mass and the blockworkaesthetic. Insulation was often not included in the traditionalcavity blockwork which gave these houses the reputation ofbeing cold. While cavity construction allows insulation to beinstalled in the cavity, the detailing should ensure that the cavitywill allow free drainage and that the type of insulation specifiedis capable of withstanding moisture.
insulation incavity
veneer tie
water proofingmembrane
weephole
concretemasonryveneer
15 seriesstructuralconcretemasonry
10 series concrete masonry veneer over 15 seriesstructural wall. Cavity should be insulated.
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residential concrete detail ing and specif ication guide
18
Waterproofing
The considerations for choice of waterproofing system are setout in the General Section. It is most important to considerappropriate and effective waterproofing strategies for concretemasonry due to its porosity. Cracks that develop between themortar and blocks are also areas of vulnerability that thewaterproofing system must be capable of bridging.
Unpainted and unsealed blockwork is an option in somecircumstances such as when using veneer construction or ingarages and uninhabited basements. It is important neverthelessto bear in mind the affect water can have on the masonry. Watercan bring salts to the surface in the form of efflorescence, leavingan unsightly and unpredictable white pattern on the surface.
Plan view of bond beam at control joint
Shrinkage control joint
verticalreinforcing
bondbeam
full heightshrinkagecontrol joint
horizontalreinforcing steel
verticalreinforcing steel
sealantboth faces
debondedbar
shrinkage central joint
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Concrete Masonry
19
Shrinkage control joints
Shrinkage control joints are necessary toensure that shrinkage cracking occurs in acontrolled manner and allows movementdue to thermal changes. NZS 4229specifies requirements for control joints.These should occur at approximately sixmetre centres and will affect theappearance of the project when themasonry is to be left exposed or painted.Applied finishes such as stucco plastershould also acknowledge the control jointto avoid consequential cracking. Thedesigner should take charge of the controljoint setout and carry out detailing asillustrated on the previous page to avoidany surprises on site.
specification
There are several New Zealand Standardsthat may be relevant to the writtenspecification. These include the following:
NZS 4229:1999Concrete masonry buildings notrequiring specific engineering design
NZS 4230:1990 Code of practice for the design ofmasonry structures
NZS 4210:1989Code of practice for masonryconstruction: materials and workmanship
AS/NZS 4548Guide to long-life coatings for concreteand masonry
NZS 4251:1974Code of practice for solid plastering
NZS 3604:1999Non specific design Light timber framebuildings
Materials
All materials should be procured from adependable source.
Where appropriate, ensure that qualityrecords are obtained and kept for easyretrieval, should they be required.
Concrete blocksshould be dry and remain so until theyare used.Manufacture must comply withAS/NZS 4455Excess moisture in any of the materialscan reduce structural quality and requirethe blocks to have to dry longer beforesurface finishes can be applied.
Steel reinforcingshould be maintained free of dirt andorganic material.
Mortarmixing ratio (cement/sand/lime/water) tocomply with NZS 4210To provide a compressive strength of notless than 12.5 MPa.
Concrete blocks stackedon pallets.
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residential concrete detail ing and specif ication guide
20
Groutmixing ratio to comply with NZS 4210. To provide acompressive strength of not less that 17.5 MPa.Spread value 450 530 mm
Sandchloride levels should not exceed 0.04% by dry weight of sand
Waterone of the most important yet overlooked components of highquality concrete. Water must be clean and free from excess alkali,salt, silt and organic matter.
Workmanship
Concrete masonry work should ideally be carried out byqualified tradesmen. As a minimum, tradesmen should haveexperience in the required areas of construction. In someinstances, such as detailed structural work, it is desirable toemploy a Registered Mason.
All concrete masonry work should be carried out underadequate supervision.
Grout all cells that
1. contain reinforcing
2. are required to be filled as part of the design requirements
Grouting should follow the procedures set out in NZS 4210.
Form construction joints in accordance with NZS 4210 betweengrout pours and between the blockwork and any hardenedconcrete.
The block layer must coordinate his work with the work of othertrades. Coordination should take place well in advance of thework being done.
The block layer must build in all elements including fixings,bolts, ties and any service requirements as called for, and/ornecessary for the completion of the job.
Once concrete masonry work is complete all block work must becleaned.
20 series
15 series
10 series
A selection of concrete masonry profiles that are available. Consultwith manufacturers to determine the full range.
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Concrete Masonry
21
construction
Planning the job
One of the most important activities when building in concretemasonry is planning the project. The economy of concretemasonry block work can only be maximised with properplanning.
Consider the module. Try to minimise the number of cut unitsand to maximise the sizes of any units to be cut. Doing so willalso serve to keep costs to a minimum. Check with the designerwho may have specified the placement of any cut units.
Plan the sequence of activities carefully. This is especiallyimportant with respect to services that will occur in masonrywalls.
Setting out
Reinforcing steel must be set out at foundation levels to fallwithin the planned location of cells.
Normally the concrete masonry requires a vertical steel setout of800 mm centre to centre spacing. Note that foundation stirrupstypically occur at 600 mm centres meaning that only one inevery four stirrups can be extended as vertical steel.
Setting out of foundations to suit the specific requirements ofthe design is also critical. These include
allowing for any specified overhangs of concrete block orveneer
allowing for set downs or insets at door openings.
Builders should take extra care when setting out services thatwill be concealed in masonry walls. This requires fullcoordination between trades such as plumbers or electriciansand the reinforcing steel trade.
Weather conditions
Wet weather can cause build up of water in the blocks, as theyare relatively porous. Excess water can reduce the strength ofgrout. This is particularly of concern where water is retained atthe bottom of, or between lifts of, grouted cells.
Rain onto fresh mortar can erode its surface, affecting theappearance and possibly the structural strength of the mortarjoints.
Cold conditions will not allow the mortar or grout to setproperly. Concrete masonry and grout should not be placed intemperatures less than 4C.
Hot weather conditions are generally not a problem for concretemasonry in New Zealand. However, prolonged dry conditionsmay warrant attention when laying or grouting the masonry.Overly dry blocks will draw moisture out of the grout or mortartoo quickly thereby affecting the bond with the blocks. It istherefore recommended that the blocks be wet lightly on thosesurfaces which will be against the mortar or grout.
Provided the blocks are not too dry the curing of the mortar andgrout does not require special care. If strong hot winds or directsunlight in the middle of the summer are anticipated it would beprudent to ensure the mortar and block surfaces are kept moistfor the first three to four days after being placed.
Protection
Builders should take care to protect finished concrete masonryfrom damage which could arise through the building process.This is particularly important with blockwork and veneer thathas been designed to be left exposed.
While in most cases it will be impractical to erect full protectionfor the masonry it should be possible to anticipate work that willcreate risks to the completed walls. Plywood sheets serve as anexcellent form of protection.
It is necessary to coordinate reinforcingplacement with block setout.
Kew House by Melling Morse Architects
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WALL TO FLOOR
INTERMEDIATE FLOOR
WALL TO ROOF
Insulation
Internal lining
Building paper continuous
100 x 50 on DPC
Reinforced concrete slab
Reinforced concrete footing
DPC over 25mm sandblinding
Compacted granularhardfill
15 series conc. masonryfoundation wall.Starter bars atrequired spacing.
Waterproofing systemextend min 50 belowfloor level
15 series conc. masonryvertical & horizontalreinforcing per NZS 4229
Unpaved G.L.
Paved G.L.
Internal linings on timberstrapping
Continuous boundary joist onDPC
Bolt connection to bondbeam per NZS 4229
Particle board flooring
Joist hanger
MDF skirtingExternal waterproofingsystem
acrylic plaster & paint
acrylic paint system
sand/cement plastersystem & paint
sealer
External waterproofingsystem
Continuous timber plateon DPC Bond beam in accordance
with NZS 4229
15 series conc. masonry
Ceiling lining on battens
Roofing onbuilding paperon wire netting
Timber trusses
Fascia
Insulation
Cast in bolt fixings
Bond beam at floorlevel
Timber strapping
100
MIN
150
MIN
residential concrete detail ing and specif ication guide
22
Internally insulated wall section
This wall section presents:
single wythe 15 series concretemasonry
building paper on the inside face ofthe masonry acting as a second line ofdefence against moisture penetration
strapping and lining on the interior
insulation between strapping
concrete masonry foundation wallacting as permanent formwork forconcrete slab on grade.
These details separate the thermal massof the concrete masonry from the interiorspace. It also allows the concretemasonry to be expressed as anarchitectural finish externally.
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WALL TO FLOOR
INTERMEDIATE FLOOR
WALL TO ROOF
Paved G.L.
Unpaved G.L.
Acrylic plaster system
Proprietary externalinsulation system
Reinforced concreteperimeter edge beam
Sand blinding oncompacted hardfill
DPC
Fix skirting & other elementsby plug & screw on DPC
Internal finishes paint system plaster system none
Reinforced conc. slab
Bond beam
Suspended ceiling systemfor services & lighting
Proprietary concrete floorsystem
Acrylic plaster system
Proprietary externalinsulation system
Bond beam
Suspended ceiling systemfor services & lighting
Concete floor system
Acrylic plasterwaterproofing system
External insulation systemButyl on plywood oninsulation on DPC
Butyl as upstand dressed &sealed into chase in mortarjoint
FALL Extend insulation andwaterproofing over butyl withsealant bead
150
MIN 10
0MI
N 50 MIN
Concrete Masonry Detai ls
23
Externally insulated wall section
This wall section presents
single wythe 15 series concretemasonry
exterior insulation and waterproofingsystem
concrete roof system
concrete intermediate floor system
reinforced concrete slab withthickened edge perimeter foundation.
This construction allows full advantage to be taken of the thermal mass in thehouse. The texture/finish of concretemasonry can be expressed internally.
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WALL TO FLOOR
WALL TO ROOF
Paved G.L.
Unpaved G.L.
Masonry ties in accordancewith NZS 4229
Sand blinding oncompacted hardfill
DPC
Skirting
Reinforced conc. slab
10 series conc. block veneer
75mm high weep holes@ 800 centres
100mm insulationInternal lining
Building paper continuousVentilated cavity
Ceiling lining on battens
Roofing onbuilding paperon wire netting
Timber trusses
Fascia
Continuous 10mm gapfor ventilation
10 series conc. block veneer
Ventilated cavity
Masonry ties. Materialto suit environment
Waterproofing on slopedplaster
Bottom plate bolted tofoundation
150
MIN 10
0MI
N 50 MIN
75 max40 min
10
residential concrete detail ing and specif ication guide
24
Concrete masonry veneer
Concrete masonry veneer has beenwidely used in New Zealand houseconstruction.
The principle of a ventilated cavity cangive a greater source of security to thehomeowner and designer alike.
As with all masonry, it is important toconsider the modular height in settingout openings and heights of walls. Thisexample shows the veneer stopping shortof the soffit lining as a way of expressingthe nature of the masonry on a veneer.This also stops the lining from meetingthe masonry off the height module.
Note the requirements in NZS 4229 andNZS 3604 for the base material andprotection for masonry ties in certainexposures.
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RAISED GROUND FLOOR
WALL TO FLOOR
Paved G.L.
Unpaved G.L.
External cladding fixed overbuilding paper
Insulation
Perimeter edge beam Sand blinding oncompacted hardfill
DPC
Fix skirting & other elementsby plug & screw on DPC
Reinforced conc. slab
Openings in wall forventilation to comply withNZS 3604
Sisalation or under floorinsulation
Particle board flooring
Timber skirting
Internal finish
20 series reinforced conc.masonry footing on concretebed
External waterproofingand insulation system
Bond beam
M16 bolt to complywith NZS 4229
Timber stringer onDPC
15 series conc. masonry
Timber strapping fixed tosolid filled cells over DPC
15 series conc. masonry
Cement/sand plaster oracrylic plaster internal finish
150
MIN 10
0MI
N 50 MIN
Concrete Masonry Detai ls
25
Externally insulated wall
This system is designed to allow atraditional external appearance. Almost any external cladding can bechosen. Timber weatherboards areillustrated here.
The internal finish should be applieddirectly to concrete masonry to allow thefull advantage of thermal mass.
Foundation crawl space
This construction detail is ideally suitedto a sloping site.
The use of concrete masonry as afoundation footing can be botheconomical and time saving, particularlyon sloping sites or those with limitedaccess.
-
SILL DETAIL
HEAD DETAIL
15 series conc.masonry
Externalwaterproofingsystem
Extend waterproofingover plaster screedto falls and under sillgenerally
Galvanised metalflashing
Interior lining
Insulation
Timber strappingBuilding paper
TImber reveal
Externalwaterproofingsystem
15 series lintelblock
Timber frame onpacking. Plugand screw tomasonry
Sealant overbacking rod
Timber reveal
Architrave
Building paper
Timber strapping
Insulation
Interior lining
Glazing in timberwindow frame
Architrave
residential concrete detail ing and specif ication guide
26
Timber window details
Timber joinery is still the preference formany homeowners. Modern timberwindows are well made and draft free. Itis important to build these windows unitsin to ensure weathertightness.
The details illustrated here indicate anappropriate method for doing so.
-
SILL DETAIL
JAMB DETAIL
HEAD DETAIL
Position frame toallow drainage fromwithin
Run waterproofing upunder reveal
Continuous sealantbead
Waterproofing system
Build up waterproofingmembrane and formdrip
Continuous sealantbead
A
A
DPC overwaterproofingmembrane andover buildingpaper
Timber reveal
Timber strapping
Interior lining
Building paper
Insulation
20 seriesrebated block.Reinforce perNZS 4229
20 series rebatedlintel block
Remove projecting sill
Insulation
Building paper
Interior lining
Timber strapping
20 seriesrebated sillblock.
InsulationBuilding paperInterior lining
Timber strapping
Timber reveal
DPC over water-proofing membraneand over buildingpaper
Waterproofing system
Concrete Masonry Detai ls
27
Aluminium window details
Aluminium is the most common materialfor exterior door and window frames inresidential construction.
These details demonstrate the use ofaluminium window frames in 20 seriesblockwork using rebated blocks. Therebated block allows a positive step forthe frame to fit against.
When using an exterior membranesystem be sure to extend it under thewindow frames prior to their installation.DPC should lap onto membrane and overbuilding paper.
Note the requirement by some windowmanufacturers to fit an angle (note A) inhigh wind areas to relieve the pressureson the sealant joint.
It is quite common to remove theprojecting profile from the sill block toachieve a more flush appearance. Notethat this may cause staining underwindows as dirt that has settled on thesill gets washed down by rain.
-
SILL DETAIL
JAMB DETAIL
HEAD DETAIL
Acrylic interiorplaster system.Neatly finish to timberframe
DPC
Form recess atopenings
Fairface concretefoundation beyond
EIFS beyond
External InsulatingFinishing System(EIFS)
15 series lintelblockDPC
Sealant
Continuous headflashing
Glazed timberdoor
Conc. slab
Rebate slab fortimber sill
Acrylic interiorplaster system.Neatly finished to timberframe
External InsulatingFinishing System(EIFS)
15 series lintelblock on end
DPC
Sealant
Glazed timberdoor
Timber packing
Timber doorhead and bead
Timber bead
Timber packing
Glazed timberdoor
Timber doorsill
Timberangle fillet
Timber doorjamb
residential concrete detail ing and specif ication guide
28
Timber door details
The external ridgid insulation systemallows the concrete masonry to be leftexposed, or receive a thin finish asillustrated here. There may be thermalbenefits to the home owner in adoptingthis strategy.
The timber frame is supported on timberpacking which is continuous andplastered over. The plaster system shouldbe reinforced across this piece.
Sealant is applied between the timberframe and the insulation system as aweather seal.
-
SILL DETAIL
JAMB DETAIL
HEAD DETAIL
Shaped timberthreshold
Sand/cementplaster system
Concrete slab
Paving level
Fairface conc.foundation beyond
Bring DPC overleading edge ofslab
Aluminium door sillframe
Aluminium doorframe with weatherstrip on botttomedge
EIFS
External InsulatingFinishing System(EIFS)15 series lintelblock
Sealant bead.Leave 50mm highgap at bottoms ofjambs for water toescape
DPC
Glazed hinged door inaluminium frame
External InsulatingFinishing System(EIFS)15 series block
Sealant bead.Leave 50mm highgap at bottoms ofjambs for water toescape
DPC
Glazed hinged door inaluminium frame
Expresscontroljoint
Expresscontroljoint
Sand/cementplaster system
Form recess at openings
Concrete Masonry Detai ls
29
Aluminium door details
These details show the aluminium doorframe set in 15 series blockwork not usingthe rebated profile. This presents greaterflexibility for the designer to positionframe in depth of block. It may be pref-erable to use rebated block profiles inopenings as this gives maximumweathering protection.
Details show that the thermal mass isfully available to the interior space as theinsulation is placed externally.
The detail shows that the upstand legfrom the sill frame across the thresholdhas been removed. This prevents it beingdamaged by being walked over.
-
SILL DETAIL SILL DETAIL
HEAD DETAIL HEAD DETAIL
10 seriesmasonry veneer
Masonry ties inaccordance withNZS 4229
Sealant betweenaluminium windowframe and sill tile
Building paper
Galvanisedmetal sillflashing.Lap oversill tile
125 x 125 x 8mm Hotdipped galvanisedM.S. angle lintel fixedback to framing
Sealant
Weep holes
Lap building paperover M.S. angle lintel
Masonry ties inaccordance withNZS 4229
TimberLintel perNZS 3604
Galvanisedmetal headflashing.
Masonry ties inaccordance withNZS 4229
Lap buildingpaper over M.S.angle lintel
Weep holesTimberLintel perNZS 3604
10seriesmasonryveneer
Masonryties inaccordancewith NZS4229
Aluminium frame withtimber reveal
Sill tiles onplaster
Timberframingwithinsulationbetween
Interiorlining
Sill tiles onplaster
Timberwindow sill
Timberwindowframe
Architrave
Continuoussupport fortimber sill.Fix overbuildingpaper
Interiorlining
Insulation
Interiorlining
Insulation
Architrave
Timberwindowframe
Interiorlining
Insulation
residential concrete detail ing and specif ication guide
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Veneer window details
The position of window frames in aveneered wall is critical to ensureadequate closure of the gap whileensuring adequate fixing for the frame.
Most aluminium window frames forresidential use are delivered to the sitewith reveals fixed in the factory. Fixingthrough the reveal, as shown, will allowthe frame to bridge the cavity.
Timber window frames, on the otherhand, may require framing support in thecavity, as shown.
Units fabricated in the factory, beforetimber and aluminium may be able tospan across the sill without fixings.
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Concrete Masonry Detai ls
31
ROOF VERGE
Bond beam
Soffit
Casement bead
Sand/cementplaster system(19mm texturedsurface)
Metal flashing
Ceiling lining on battens
Metal roofing on buildingpaper
Timber purlins/rafters(cantilevered verge)
Solid blocking
Internal linings over50mm timber strapping
Insulation
Building paper
PARAPET / METAL ROOF
Bond beam
Internal linings onceiling joists/rafters
Furring to fallsAcrylic plastersystem
Proprietaryexternal insulationsystem
Metal flashing dressed &sealed into chase inmortar joint
FALL
Bond beam
Metal roofing to falls
PARAPET / METAL ROOF
Bond beam
FALL
Butyl as upstand dressed& sealed into chase inmortar jointButyl on plywood on75x40 furring to falls
Proprietaryexternal insulationsystem
Acrylic plastersystem
Internal linings onceiling joists/rafters
Bond beam
15 series conc.masonry
Gutter overflow.Opening size tomatch downpipe.Position belowgutter freeboardheight.
Furringto falls
Metal roofing to falls
Insulation
Roof details
The use of sand/cement plaster allows asmooth uniform texture finish using amaterial similar in nature to concretemasonry.
Care must be taken to:
ensure adequate bond of sand/cement plaster to concrete masonry
follow control joints in masonrythrough sand/cement plaster
A suitable paint finish will provideweatherproofing.
The use of an internal gutter suits manyof the contemporary expressions ofarchitectural design. Dimensions of sucha gutter should be to suit the expectedrainwater flow, but in no case should itbe less than 600 mm for ease ofcleaning.
Provide secondary overflow capacity toensure rainwater does not back up insidehouse.
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residential concrete detail ing and specif ication guide
32
BLOCK WALL / VENEER JUNCTION
Internal liningson timber strappingon building paper
Timber floor joist
FlooringExternal waterproofingsystem
acrylic plaster & paint
acrylic paint system
sand/cement plastersystem & paint
sealer
Insulation
25 seriesbond beam
20 series concreteblock
10 series concreteblock veneer
Timber platebolted to bondbeam on DPC
Blocking
Ceiling on timberstrapping
Suspended floor details
A hybrid form of construction withconcrete masonry ground floor structureand a lightweight structure above. Thedurability aspects and appearance ofconcrete masonry is continued with 10series veneer over the timber framing.
Suspended deck details are critical to getright particularly if they sit above interiorspaces.
When the concrete block module is seenfrom outside, it is critical to ensure thefull module carries through floor leveland that the detailing reflects this.
Services details
As with most forms of concreteconstruction, it is critical to plan forappropriate services reticulation whendetailing in concrete masonry.
When using masonry veneer constructionit is tempting to reticulate services in thecavity but this is specifically prohibited inNZS 4229.
When using partial fill concrete masonry,dropping services from ceiling level in anempty cell can make the job much easier,particularly as a retrofit. It is advisable tocast sleeves into the bond beam to allowthese services to be reticulated easily.Casting in additional sleeves toanticipate future alterations is alsorecommended.
-
Concrete Masonry Detai ls
33
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Insulating Concrete Formwork
35
Insulating Concrete Formwork
General . . . . . . . . . . . . . . . . . . .37
Design Issues . . . . . . . . . . . . . .38
Specification . . . . . . . . . . . . . .39
Construction . . . . . . . . . . . . . . .41
Details . . . . . . . . . . . . . . . . . . .43
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Insulating Concrete Formwork
37
Insulating concrete formwork (ICF) is a proprietary formwork system forconcrete that is left in place tobecome part of the building. ICF systemshave been available in New Zealand forthe last 10 years and during that timehave been increasingly used for bothcommercial and residential construction.ICF construction has been used for some30 years in Europe, where concreteresidential construction is quite common.
Block systems are widely available in New Zealand. Plank and panel systemsare available internationally but notcurrently in New Zealand. The forms aretypically made of expanded polystyrene,a closed cell polymer. The reinforcedconcrete core provides all the structuralcapacity of the wall.
The main advantages of these systemsare:
excellent insulation properties
low levels of air infiltration
blocks are easy to lay and fill
relatively easy to run servicesconcealed in polystyrene layer. This istrue of both new construction andrefitting work.
long life expectancy
A contemporary housebuilt using insulatedconcrete formwork.
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residential concrete detail ing and specif ication guide
38
design issues
Although the principle of ICF construction is similar to that ofconcrete masonry, there are some important differences for thedesigner to consider.
Module
The modular height of systems available in New Zealand istypically 300 mm. As with concrete masonry, it will be moreeconomical to work to the modular height for openings and wallheights. Most systems mechanically lock together along top andbottom edges.
ICF systems are available in widths of 200, 250 and 300 mm.Unit widths correspond to different concrete thicknesses. Thewider blocks offer increased structural capacity, little if anyinsulating increase and potentially reduce the interior floorspace. The greater thickness will give greater reveal depth atopenings which is often sought after by designers.
ICF blocks are relatively long, in the order of 1000 to 1500 mmwith many bridges between the faces. This allows the blocks tobe easily cut to length without compromising the structuralqualities. With block sizes like these, it is easy to see how thesesystems can be laid so quickly.
Proprietary systems
This part of the guide has been prepared with informationobtained from the suppliers of ICF blocks in New Zealand. Asmuch as possible, it has been the intention of the writers topresent this information in a generic manner, thereby notfavouring any one supplier.
As soon as a particular system is adopted it is advisable that thedesigner confirm all details with the particular supplier.
Applied finishes
ICF systems comply with NZBC durability requirements,provided the blocks are appropriately finished or clad forprotection from the effects of UV radiation and weather. MostICF suppliers require that claddings or finishes are approved foruse with their system. Modified acrylic plaster and paint systems,timber strapping with weatherboards, concrete masonry andstone veneers are examples of external claddings that ICFsuppliers have recommended for use.
Modified acrylic plasters, plasterboard or fibre cement sheet aretypically used as internal linings. ICF suppliers will give guidanceto the methods of fixing linings using adhesives and screws.
Typical ICF block format. Confirm thedimensions with the selected supplier.
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Insulating Concrete Formwork
39
Detailing fixings
One of the most important detailing considerations with ICFsystems is that of fixings. This includes fixings for bothstructural and architectural elements. The formwork units, asthey are made of polystyrene, offer limited fixing capacity. Tomake allowances for timber skirtings to be secured, the fixing ofwindows into openings and joinery fittings to be positioned, it isnecessary to cast in timber fixing blocks. These are typically 150 mm long and are secured into the concrete core by pairs ofnails that protrude off the back face. This apparently lowtechnology detail is very effective, provided the necessaryplanning has allowed them to be in the right places.
Structural elements such as concrete flooring systems can beaccommodated and are installed after the concrete has been castto the soffit level. The seating depth can vary between 50 and 75mm. The method for fixing timber floor framing to ICF walls isto secure a stringer on fixings cast into the concrete core.
specification
It should be the objective of the specification writer to structurethe documents in such a way as to encourage competitivepricing. Fortunately there are several suppliers of the forms inmost parts of New Zealand.
Once a system has been selected it is advisable to confirm alldetails and other design issues with the selected manufacturer.This includes wall thicknesses, building in details, steelreinforcing requirements and construction requirements.
It is desirable to structure the ICF sub-contract on the basis ofengineering design and supply. It may also be possible to includethe erection of the system in that subcontract.
A Producer Statement: Design, or some other evidence ofstructural capacity should be required by the specification. Thiswill assist the Territorial Authority in approving its use.Manufacturers literature and guarantees should also be requiredby the specification.
Standards referred to:
NZS 3101: 1995The design of concrete structures
NZS 3104: 1991 Specification for concrete production high grade and specialgrade
NZS 3109: 1997Concrete construction
NZS 3402: 1989Steel bars for the reinforcement of concrete
Materials
There is at present no New Zealand Standard for themanufacture of ICF units. Accordingly the designer shouldreserve the right to approve the supplier.
Timber inserts facilitate fixing of doorframes, skirtings and other joinery items.
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residential concrete detail ing and specif ication guide
40
ICF Blocks should be made of fire retardant materials.
In situations where fire resistance ratings are required. Thesemust be specified as not all ICF blocks provide adequate fireresistance.
Concrete infillto achieve a minimum compressive strength of 20 MPa.Maximum aggregate size to be 14 mm. Concrete slump shouldcomply with the ICF manufacturers requirements. A 100 mmslump is typical. Expansive additives must not be used in anycircumstances as these can blow out the forms.
Steel reinforcingto comply with NZS 3402.
Workmanship
Erection and filling of the system should be carried out either bythe ICF supplier or by a firm approved by them.
The installation should be carried out by persons withexperience in this type of work. All necessary and appropriateequipment and construction techniques to be employed.
The blocks are fitted together and propped in place before fillingwith concrete. Temporary wire ties may be necessary to preventthe blocks floating on the concrete fill. These should be installedevery four courses.
Allow to build in all fixings and services as detailed and requiredby various trades. Typically, such fixings are supplied by therelevant trade or by the builder, to ensure they are correct.
The ICF trade must coordinate with all other trades.
Allow to locate and form construction joints in accordance withNZS 3109.
Before placing concrete, ensure all cells are clean and reinforcingis secured in place. Consolidate concrete with a max 25 mmdiameter poker vibrator or by rodding. Vibration should ensurethat all cells are filled with well compacted concrete. Extent andheight of lifts to be in accordance with ICF manufacturersrecommendations.
Significant construction tolerances for ICF are to be expectedgiven the nature of the material. It is prudent to limit tolerancesand to ensure subcontractors are aware of them so they canmake appropriate allowances. Recommended limits are asfollows:
Deviation from plan location 20 mm
Deviation from vertical within a storey 10 mm per 3 m
Relative displacement between load 5 mmbearing walls in adjacent stories intended to be in vertical alignment
Deviation from line to planAny length up to 10 metres 5 mmAny length over 10 metres 10 mm
Deviation from horizontalAny length up to 10 metres 5 mmAny length over 10 metres 10 mm
Concrete floor systems can be easilyaccommodated in ICF construction.
Diagram showing ICF components.
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Insulating Concrete Formwork
41
construction
Planning the job
Due to the speed with which ICF systems can be erected, it isimportant to plan well ahead.
Follow the manufacturers recommendations for the height ofeach lift.
ICF blocks are easy to cut, allowing opportunities to deviatefrom the block module.
It is important to consider, from a construction viewpoint, thatthe ICF walls have no structural capacity until the concrete coreis cast. Therefore it is important to provide adequate proppingand support for these elements until the concrete has achievedthe appropriate structural strength.
Setting out
As with other systems covered in this guide, it is important to setout reinforcing to suit the ICF block width. This must beconfirmed prior to casting of foundations.
The ICF forms can be used for internal and external walls.
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residential concrete detail ing and specif ication guide
42
Weather conditions
Due to its insulating qualities, in theory concrete can be placedin colder conditions than it can into other types of formwork.However, this is rarely a factor in New Zealand conditions.
The forms themselves can be placed in most weather conditions,although the unfilled forms are susceptible to displacement inhigh winds. Concrete can be placed in the forms when it israining provided measures are taken to remove water in thebottom of the forms, which if left will mix with the concretethereby reducing its strength.
Curing and drying
ICF systems enhance concrete curing by slowing waterevaporation. This effect can increase concrete strengths.Obtain, and comply with the ICF and coating manufacturersrecommendations for drying times prior to the application ofsurface finishes.
Protection
ICF is vulnerable to mechanical damage particularly beforecladdings are applied. Protection, such as plywood sheeting,should be considered in areas of high risk during construction.
At exposed corners and edges PVC protection is recommendedas part of the cladding system.
Prolonged exposure to sunlight can cause surface deteriorationof the polystyrene. If the surface becomes scaly after a period ofexposure, this scaliness must be removed prior to the applicationof surface finishes. The minor deterioration that may occur willhave no effect on the structure of the wall. Some reduction of theinsulation properties may occur, depending on the depth ofdeterioration.
It is important to prop ICF units appropriately until concrete has set.
Stone and other veneers can be used to give thehouse a traditional appearance.
-
WALL / SLAB
CONCRETE FLOOR
CONCRETE ROOF
100
150
Reinforcing mesh
Insulation over DPM
Fix Butyl into chase cut into wall.fix 90 PVC angle cap to Butyledge and seal in place. Plasterdown onto PVC angle
Butyl on Plywood base
Concrete slab. Prop in place untilconc. is cured
Metal frame suspended ceiling
Construction joint
ICF block system
Reinforcing
Reinforcing
Internal finish
Rough broomed surface toensure good key
Cut hole in block at each conc.beam
TImber formwork
Internal finish
Skirting fixed to intermittenttimber block cast into conc.
Reinforced conc. topping
Conc. beam & timber infill floorsystem
Reinforcing mesh
ICF block system
Reinforced conc.slab
DPC
Sand blindingReinforced concretefooting
PVC starter strip,forming a drip edge
ICF block systemExternal finish Internal finish
Compacted granular hardfill
Unpaved G.L.
Paved G.L.
Metal frame suspended ceiling
FALL
Concrete topping to falls
Reinforce corners ofplaster systems
Construction joint
External plaster finish
External plaster finish
Insulating Concrete Formwork Detai ls
43
Wall section
These details indicate how the ICFconstruction system can be combinedwith various concrete floor systems.
The roof details indicate a concrete floorslab system with topping formed to falls.With all parapet conditions it is importantto make allowance for overflow in caseprimary drain becomes blocked.
Insulation is shown on top of roof slab toallow thermal mass to help moderateindoor temperatures and to preventcondensation that may develop in certainconditions.
Suspended floor detail indicates precastbeam and infill system.
A suspended ceiling can be included toconceal services and the soffit of theflooring system. With appropriateplanning and good workmanship, it ispossible to leave these surfaces exposed,thereby saving the cost of the ceiling,enjoying greater floor/ceiling heights andthe thermal mass benefits of theconcrete.
ICF can be used as permanent formworkfor foundations.
-
WALL / SLAB
TIMBER FLOOR
ROOF OVERHANG
150 10
0
ICF block wall
Internal lining
Ceiling battensInsulation
DPC
Top plate fixed @750max ctrs withcast in bolts
Connection platebetween top plateand truss
Timber truss
Timber stringer,fixed @ 750maxctrs. with cast inbolt
Soffit lining
Gutter
Fascia board
Building paper& timber purlin
Roofing
Malthoid strip betweentimber and concrete oruse H3 treated timber
Joist hangerContinuous slot cut inblock wall for stringer
Timber joistsFlooringExternal finish
Skirting fixed tointermittent timber blockcast into conc.
Extend insulationdown to bottomof foundation
PVC channel
SkirtingReinforced concrete slab
DPC
Compacted sand blinding
Granular hardfill
ICF block system
Internal finishExternal plaster finish.Extend to ground level
ICF block system
Paved G.L.
Unpaved G.L.
residential concrete detail ing and specif ication guide
44
Wall section
The details on this page indicate atraditional sloping roof with overhang.Planning is required to cast inappropriate fixings for structural andarchitectural elements, as ICF will notsupport or transfer any loads.
The suspended timber floor must besecurely anchored to the wall to transfervertical and lateral loads. This shouldalso coincide with a horizontal bondbeam. As the intermediate floor acts as adiaphragm in this case, only onehorizontal bar is required in the bondbeam. The timber frame floor/ceilingassembly allows electrical services to beeasily reticulated, but acousticperformance is somewhat compromisedin comparison with a concrete system.
The concrete slab on grade forms aperfect base for the insulated concreteformwork system. It is important tocoordinate reinforcing steel starter barsand fixings for skirtings and the like.
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HEAD DETAIL
JAMB DETAIL
SILL DETAIL
Corner strip
Form dripedge
ICF blocksystem
ICF blocksystem
Timber reveals
Timber packer
Cornerstrip
Internal finish
PVC flashing
Intermittent H3timber blocks.Fix galv. nailsskew nailed totimber & cast inconcrete infill.
Aluminium window section
External plaster finish
Intermittent H3timber blocks.Fix galv. nailsskew nailed totimber & cast inconcrete infill.
Internal finish
Timber reveals
Timber plate
Internal finish
Intermittent H3timber blocks.Fix galv. nailsskew nailed totimber & cast inconcrete infill.
ICF blocksystem
PVC flashing
Sealant bead
Externalplasterfinish.
Timber reveals
Aluminium windowsection
Sealant
Externalplasterfinish.
Aluminium flashing
Cornerreinforcing
Insulating Concrete Formwork Detai ls
45
Aluminium window details
The key to fitting doors and windows intoopenings in ICF partitions is to plan for,and cast in, appropriate fixings. Thesefixings must be H3 treated or higher, asthey are generally in full contact withconcrete. These fixings are intermittent,about 150 mm long at 450 mm centrespacings. The nails on back help anchorthe timber to the concrete.
These details also make use ofaluminium flashings and sealant toensure a weathertight opening. Theflashings must be compatible with theexterior finishing systems and fixed in amanner that will not cause the acrylicplaster system to break down.
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HEAD DETAIL
JAMB DETAIL
SILL DETAIL
ICF blocksystem
Modifiedacrylicplasterfinish
Intermittenttimber blocks.Fix galv. nailsskew nailed totimber & castin concreteinfill.
Timber windowframe
External finish. Carryunder flashing.
Fit timber sill overflashing & timberpacking
ICF blocksystem
Timber plate
Timber sill
PVC flashing
Modifiedacrylic plaster.Return atreveal
Internal finish.Return toreveal
Cornerprotection
Sealant
Sealant
Cornerprotection
Form dripedge
Cornerstrip
Sealant &backing rod
Sealant &backing rod
ICF blocksystem
Internal finish
Timber windowframe
Cornerstrip
Sill flashing
Continuous H3timber, shapedto fall
residential concrete detail ing and specif ication guide
46
Timber window details
These details, like those on the facingpage, rely on the fixing capacity of castin timber blocks.
The interior finishes here are shown toreturn in to the window frame as a reveal.This is effective in creating a massivelook to the walls.
External corners of ICF are vulnerable andmust be protected with PVC cornersintegrated with the plaster system.
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SILL DETAIL
JAMB DETAIL
HEAD DETAIL
Shaped Timberon DPC
Step backconcrete slabedge to suitreveal
Aluminium doorframe withtimber reveals
Reinforcedconc. slab
ICF blocksystem
Intermittent H3timber blocks.Fix galv. nailsskew nailed totimber & cast inconcrete.
ICF blocksystem
Form dripedge
Back sealantbefore planter
Corner strip
Aluminium doorframe withtimber reveals
Intermittent H3timber blocks.Fix galv. nailsskew nailed totimber & castin concreteinfill.
Front sealantafter planter
Back sealantbefore planter
Corner strip
Externalplaster finish
Aluminiumdoor frameover sillflashing
Lining
Aluminiumsubframe
Front sealantafter planter
Paving level
Insulating Concrete Formwork Detai ls
47
Aluminium door details
It is good practice to step back theconcrete slab edge at door openings toavoid an awkward and vulnerable silloutside the door. This requires particularcoordination between the concreteplacer, ICF contractor and metal door andwindow supplier.
It is also advisable to allow for athreshold that is robust and easy to passover, this may require the aluminiumframe profiles to be modified.
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SILL DETAIL
JAMB DETAIL
HEAD DETAIL
ICF block system.EPS stripped.Plaster smooth
Reinforced conc.slab
FlooringTimber door & sill.Recess sill into slab.
ICF blocksystem
Exteriorfinishedplaster
Intermittenttimber blocking.Fix galv. nailsskew nailed totimber and castin concrete infill.
Interior finish.Return to reveal
Corner strip
Aluminiumflashing
Timber door &frame
Interior finish.Return to reveal
ICF block system
Cornerstrip
Exteriorplasterfinished
Intermittenttimber blocking.Fix galv. nailsskew nailed totimber and castin concrete infill.
Sealant &backing rod
PVC flashing.Plug & screwinto conc.
Slope toform dripedge
Timber door &frame
Sealant
SealantSealant &backing rod
Butyl rubber sillflashing
Paving level
residential concrete detail ing and specif ication guide
48
Timber door details
The timber frame is set in the centre ofthe massive ICF wall. This massiveness isaccentuated by returning the interior andexterior wall finishes into the reveal.
Careful coordination of the rebate for thedoor sill will allow a near seamlesstransition from inside to out.
All timber must be separated fromconcrete by DPC.
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HIGH THERMAL MASS DETAIL
HYBRID CONSTRUCTION DETAIL
150 10
0
Exterior insulationsystem
Interior lining
Exterior finish systemDPC
Paved G.L.
Unpaved G.L.
Granular hardfill
Internal plaster finish
ICF block system.Interior EPS removed
Extend plasterfinish to footing
Reinforced concretefooting
Sand blinding
DPC
Reinforced conc.slab
Timber framing
Continuous topplate fixed @750max ctrs withcast in bolts
Internal plaster finish
ICF block system
Exterior finish system
Insulating Concrete Formwork Detai ls
49
Hybrid construction detail
It may be desirable to combine structuralsystems as this detail indicates.
The important coordination exercise hereis to ensure that the timber framing is setout to allow the exterior finishes tocontinue flush from the ICF to the ExteriorInsulation Finishing System.
Note that the acoustic separationprovided by this timber framed floor isminimal.
Refer to the manufacturers literature forguidance on details that can improveacoustic performance.
High thermal mass detail
To overcome the thermal mass beingseparated from the internal space, it ispossible to remove the inner skin of ICFto reveal the concrete cores which canthen be plastered smooth to a finish thatis tough and durable.
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SILL
HEAD
FOUNDATION
Timber reveals
Timber plate
Timber block
Internal fininsh
ICF block system
Tile sloping sill on 9mmfibre cement board onshaped timber
2 coats waterproofingmembrane
Concrete masonry veneer
Aluminium window joinery
MS angle
Concrete masonry veneer ICF Block system
Aluminium flashing
Lining
Timber blocks. Fix galv. nailsskew nailed to timber & cast inconcrete infill.
Aluminium Window section withTimber Reveals
Veneer ties
Veneer ties extendingto vertical reinforcing
Cavity
Waterproofing membrane
Concrete masonry veneer
Skirting & lining on intermittentfixing blocks
Internal finish
DPC
Sand blinding
Granular hardfill
Unpaved G.L.
Paved G.L.
Weep holes @ 800 crs
Cavity
2 coats waterproofingmembrane
Fibre cement sheet
Veneer ties extending tovertical reinforcing
Strip outer face of ICF
ICF block system
Reinforced conc. slab
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Concrete masonry veneer
It is possible to combine the excellentdurability and appearance of concretemasonry with the insulating qualities ofICF.
Waterproofing of the ICF outer face (in thecavity) is usually by a painted on systemsuch as bituminous paint.
The veneer (10 series) must be secured tothe structure by way of ties that areembedded in the concrete cores. This willrequire special attention to coordinationof ties with anticipated joints.
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PARAPET
PARAPET
OVERHANGING VERGE
Ceiling batten
Rafter fixed to block with galv.bolt.
External finish
Steel reinforcing
Plywood base fixed to timber framing
Stringer fixed to block with galv. bolt.
Fascia
Building paper
Internal finish
DPC
DPC
External finish
Slope top of blocks in towards gutter.
Purlins onedge
Slope top of blocks in towards gutter.
Joist hanger
Flashing
Soffit
ICF block system
ICF block system
ICF block system
Reinforcing
Fix Butynol into chase in block, fix 90PVC angle cap to Butynol edge andseal in place. Finish Plaster downonto PVC angle
Fix Butynol on Plywood base to formgutter as shown
Apply sealant in chase then insertflashing.
Flashing
Roofing on purlins
Roofing
Timber rafter
Ceiling batten
Top plate embedded in ICF block.12mm Galv. bolt cast in Conc.
Insulation
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51
Roof details
Providing adequate and appropriatefixings for additional structural orarchitectural elements is critical. All threeof these details show typical fixings thatmust be allowed for.
Ensure adequate provision is made foroverflow should the primary system blockup. Internal gutters should be wide toallow ease of service and deep enough toaccommodate the expected runoff.
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Timber Decking
Linings
Insulation
Aluminium Door section
Linings
Precast concrete slab
Reinforcing
ICF block system
Timber decking
Insulating plasterboard lining
Waterproofing membrane onConc. roof
Construction joint
Precast concrete slab
External finish
ReinforcingICF block system
FALL
Construction joint
WaterproofingMembranecarried upunder doorjoinery.
Reinforced Conc. topping
Fix waterproofing membraneinto chase cut into wall. Fix90 PVC angle cap toMembrane edge and seal inplace. Plaster down ontoPVC angle
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Terrace details
Raised terraces over living space are nowvery popular. Detailing of terraces pres-ents a number of challenges in
allowing ease of transition inside vs.outside
preventing water ingress at dooropenings
preventing water ingress at walls,especially at construction jointbetween slab and upstand
A step in raised concrete floor levelsrequires a special coordination effort toensure continuity of structure andsupport of the concrete flooring systems.
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53
Services
ICF present the easiest way of reticulatingservices of any concrete structuralsystem.
Services up to 40 mm, depending on thethickness of the polystyrene face, can beaccommodated by cutting away a chase.Generally these services must be securelyfixed to the concrete core by way oflamps and tappets. The chases must thenbe covered over by the finishing process.Plasterboard is generally able to spanacross the gaps but care must be taken tonot place a sheet joint on the chase.
Plaster systems will require a bandage.The supplier should be contacted fordetails.
Services can also pass through the wallsbut positions and sizes must beapproved by the manufacturer.
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Precast Concrete
55
Precast Concrete
General . . . . . . . . . . . . . . . . . . .57
Design . . . . . . . . . . . . . . . . . . .58
Specification . . . . . . . . . . . . . .60
Construction . . . . . . . . . . . . . .62
Details . . . . . . . . . . . . . . . . . . .65
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Precast Concrete
57
The development of concrete precasting techniques in thiscountry has allowed reinforced concrete to competefavourably with other forms of construction. Curiously ithas not made a serious entry into the residential constructionmarket until the past 10 years. This later period has coincidedwith the development of proprietary self insulating precastsystems. Details of such systems are presented in this section butthere is also plenty of scope for applied insulation systems.
Concrete precast methods were pioneered in the US early in the20th century. The New Zealand industry is well developed andgenerally acknowledged as a world leader. There are good suppliesof the raw materials and technology in most parts of the country.
Precasting, whether done in factory conditions or on site, offersthe opportunity to control the quality to a high standard.
Advantages of precast concrete construction systems include thefollowing:
quality control the quality is better able to be controlled bycasting multiple units in the same mould, by casting walls flatrather than standing upright and through the ability to bettercontrol environmental conditions.
lower costs for the reasons noted above.
finishing options inherent in solid concrete construction
interesting shape and texture possibilities
speed of construction with off site production the panelsand other precast elements can be made while the site isbeing prepared. It is possible to set up a house in two dayswith an experienced crew.
The Pascal Housein Auckland byCook, Hitchcock& Sargisson.
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residential concrete detail ing and specif ication guide
58
Precast flooring systems are ideal for use in a concrete home. Anumber of different flooring systems are currently available inNew Zealand. These proprietary systems have been developed forcommercial buildings, but are also suitable for the span andloading demands that can be anticipated in residentialconstruction. Suppliers generally offer design services which canbe incorporated into the overall structural design philosophy.These flooring systems can be categorised as follows:
flat slab
hollow core slab
rib and infill
steel tray permanent formwork
The systems all offer excellent stiffness, durability, acoustic andthermal performance, they can be planned to includepenetrations and openings and are cost competitive with timberflooring systems. They are also not prone to annoying squeaksthat can occur with timber floor systems.
design
As with in-situ concrete (refer to In-situ section), there arechoices to be made with respect to the following:
Surface Texture
There are many opportunities with precast concrete to createinteresting surface textures. Finishing techniques for the formed(underside) face are described in the surface finishes section. Thescreeded face (topface) generally becomes the second side orback. Texture options include:
exposed aggregate
acid etched
ground and polished
board formed
Colour
Concrete used in precast work can be coloured. This can beachieved with colour throughout the mix, or alternatively, it ispossible to place coloured concrete on the exposed face withstandard concrete behind.
Panel or unit format
The size and layout of individual panels is essentially limitless.However, there are some practical limitations. Typical parametersthat may dictate panel size are:
the area available for casting (when casting on site). This maybe an area of a floor slab or a separate temporary casting slab.
efficient repetitive use of special moulds
site access
capacity of lifting equipment or transport
the positioning of panel joints relative to openings.
Precast concrete systems include floor units in addition to walls.
Combining surface finishes can help breakdown the scale of a building.
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Precast Concrete
59
there are also aesthetic considerations to be made. Panel sizewill dictate joint set out and affect scale, texture and surfacearticulation of the house design.
The designer must also take into account panel thickness. Thereare structural aspects to consider for both transport andpermanent positions. The designer may be particularlyinterested in panel thickness when considering opening revealdepths and thermal mass benefits. Commonly panel thicknessvaries between 100 mm and 150 mm.
Jointing Details
The width and depth of joints between panels, as well as theprofile of the panel edges, must be considered by the designer.Examples of weatherproofing details are shown to the left, themost commonly used detail in the face-sealed joint. Otherconsiderations include how connections are made betweenpanels, to the floor, and to any other structural or non-structuralelements. These deliberations will most certainly include thestructural designer for the project. Options include expressingplates and bolts, countersinking and plastering over weldedplates or to conceal entirely by using pressure grouted tubes.
Edge details
Individual panel edges, especially when exposed to view, are adesign opportunity. These considerations are best made in thecontext of the joint design but should also look at corners,openings, top edges and junctions to other materials. Panel edgesare vulnerable, especially during placement of panels. It is verydifficult to successfully cast a crisp 90 corner on any concretepanel, it is therefore advisable to chamfer the corners.
Typical panel jointing details.
Sandwich constructionallows concrete panelto be left exposedinside and out.
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Insulation and weatherproofing
Although more waterproof than other forms of concrete, such asmasonry, precast concrete is still permeable to water and requireswaterproofing. Waterproofing can be achieved by application ofacrylic paint systems, which can be applied direct or as part of aplaster finish system. Veneer cladding systems can also providethe required waterproofing. Insulation can be placed on theexterior, interior or between skins of concrete. This latterstrategy has given rise to a number of specialist panel systemswhich allow all the positive aspects of concrete to be realisedwithout compromise. These systems make use of a polystyrenesheet, between an outer skin or veneer of concrete, and an innerskin which typically acts as the structure. The two faces are heldtogether by thermally non-conductive ties which are cast intoeach wythe.
specification
Designers have a choice to make between proprietary sandwichconstruction and the traditional forms of precast. If the choice isto use a proprietary system, the specification should be genericto allow a range of proprietory systems to be evaluated.
A proprietary system supplier may be required to provideProducer Statements, guarantees and constructionrecommendations.
It may be prudent to require the contractor or precaster toproduce sample panels for evaluation of such aspects as surfacefinishes. Work should not be allowed to proceed without thedesigners approval of these samples.
The Standards which apply to precast concrete construction areas follows:
NZS 3101:1995Concrete Structures Standard The design of concrete structures
NZS 3104:1991Specification for concrete production High grade and special grade
NZS 3109:1997Concrete construction
NZS 3112Methods of test for concrete
NZS 3113:1979Specification for chemical admixtures for concrete
NZS 3114:1987Specification for concrete surface finishes
NZS 3402:1989Steel bars for the reinforcement of concrete
NZS 3121:1986Specifications for water and aggregate for concrete
NZS 3421:1975Specification for hard drawn mild steel wire for concretereinforcement
Sandwich construction detail.
Joining plate can be left exposed as a design feature.
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Precast Concrete
61
NZS 3422:1975Specification for welded fabric of drawn steel wire for concretereinforcement
Materials
All materials should be procured from a dependable source.
Where appropriate, the builder must ensure that quality recordsare kept for all precast concrete work. These records must beeasily retrievable should they be required.
FormworkFormwork requirements are detailed in NZS 3109.
Reinforcing steelTo comply with NZS 3402, NZS 3422.
ConcreteReadymix concrete to the specified compressive strength and tothe requirements of NZS 3104.
Special aggregates For special finishes specify the aggregate type, colour, size, rangeand depth of exposure. All aggregate to comply with NZS 3121.
Lifting inserts Proprietary lifting devices are preferable. It is important tomatch the lifting inserts with the apparatus that will be used forlifting and the processes that will be adopted for casting andlifting.
Steel connection platesIt is recommended to galvanise any mild steel fixings that will beexposed to weather.
Workmanship
Construct formwork in the configuration necessary to producethe required set out and detail of panels. Pay particular care toedge details.
The construction and casting of panels should be carried out bytradesmen experienced in precast concrete construction.
Place and cure concrete to produce the specified finishes andtolerances. Curing should be carried out for at least 7 days.
Surface finishes shall be as specified by the designer and asdefined in NZS 3114.
Allow to cast in all items required for fixings or services. Thisrequires coordination between the trades before the panels aredesigned and cast.
The installation should be carried out by contractors experiencedin precast construction. All necessary components such asgaskets, sealants and flashings should be supplied and fitted.
Rigging and lifting must be done using the lifting pointsspecified. Take care not to knock or drag panels along theground.
Panels must