nba structural survey

Structural Survey of the

Newcastle Bangladesh

Association building

March 2011

successful people, projects and

performance

Quality Management

Job No CS/049325-03 Doc No. structuralsurvey/002

Title Structural survey

Location Newcastle Bangladesh Association building(s)

Document

Ref CS049325/structuralsurvey/001

File reference G:\York Work\Jobs\CS-049325-03 Structural Survey - Workshare

Agreement\Reports\structural survey\Structural Survey Report.docx

Date 17 March 2011

Prepared by Sam Parker Signature

Checked by Gary Robson Signature

Authorised

by Gary Robson Signature

Issue No Reason for change Author Date Issued Status

01 First Issue to Durham Office Sam

Parker 17/03/11

Draft

02 Insertion of budget costs to section 4

& 5 J Mason 21/03/11

Final

Name Role

Glen Pendleton Community Assets Co-ordinator

DOCUMENT HISTORY

DISTRIBUTION

Contents

CS-049325-03/structuralsurvey/001

17th

March 2011

Page i

Contents

1. Executive Summary 1

2. Existing Conditions 2

2.1 Site Location 2

2.2 General description 2

2.3 Details of design criteria for existing structure 2

2.4 Site Survey 2

3. Observed Defects 3

3.1 General 3

3.2 Causes of structural defects associated with the ground 3

3.3 Causes of structural defects associated with the structure 3

3.4 Plan of Buildings 4

3.5 Elevation 1 5

3.6 Elevation 2 6

3.7 Elevation 3 7

3.8 Elevation 4 8

3.9 Elevation 5 9

3.10 Elevation 6 10

3.11 Elevation 7 11

3.12 Elevation 8 12

3.13 newer additions to original buildings 13

3.14 Internal Defects 14

3.15 Boundary Walls 15

4. Further investigations required 16

5. Recommendations 17

Executive Summary


17th

March 2011

Page 1

1. Executive Summary

A visual structural survey was carried out by Sam Parker and Richard Fothergill on

Thursday 3rd March 2011. Access was granted to the property by Mr. Foysel Ahmed.

There were no intrusive survey works carried out i.e. trial pits and drainage surveys.

There was no access to the roof.

In general the buildings on site are in a very poor state of repair. There is evidence

throughout the structures that foundation movement has occurred / still is occurring

causing major structural damage.

Temporary measures could be put in place to halt the progression of some of the

more serious defects but to have a full understanding of the causes of the movement

to determine the best course of final remedial action to take, further investigations are

required.

Temporary measures could include the ‘stitching’ of the large cracks with stainless

steel helical bars grouted in the mortar joints.

Localised underpinning of the worst affected walls could be carried out although this

is an expensive option. This option could also create localised ‘hard spots’ which

could cause further differential settlement.

Further investigations that should be considered are as follows:

• Trial holes to determine size and depth of foundations and nature of

underlying soils

• Drainage survey (condition and pressure testing) to confirm no major defects

• Roof survey (requiring access) and exposing of roof bearings from within the

buildings

Existing Conditions


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March 2011

Page 2

2. Existing Conditions 2.1 SITE LOCATION

The buildings included in this report are all those sited at the Newcastle Bangladesh

Association off Elswick Road.

2.2 GENERAL DESCRIPTION

The older established buildings are two storey and are of brick construction with a

composite steel beam and concrete roof. The majority of the later additions appear to

be of concrete block construction with concrete render.

2.3 DETAILS OF DESIGN CRITERIA FOR EXISTING STRUCTURE

There have been no archive or historic drawings or reports issued and no intrusive

investigations were carried out so the foundation types are unknown. The age of the

building implies that the foundation type may be brick corbelled footings which were

generally constructed at a relatively shallow level.

2.4 SITE SURVEY

A visual structural survey was carried out by Sam Parker and Richard Fothergill on

Thursday 3rd March. Access was granted to the property by Mr. Foysel Ahmed.

There were no intrusive survey works carried out i.e. trial pits and drainage surveys

etc.

There was no access to the roof.

Observed Defects


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March 2011

Page 3

3. Observed Defects

3.1 GENERAL

The following pages show elevation photographs of the various walls of the buildings

and highlight any significant structural defects visible from ground level.

Possible causes of the defects are shown below.

3.2 CAUSES OF STRUCTURAL DEFECTS ASSOCIATED WITH THE GROUND

• Differential Settlement induced by unequal foundation pressures arising from

such factors as extensions added to existing buildings or concentrated loads,

for example under chimneys

• Ground subsidence and heave due to volume changes in clay soils

• Movement due to consolidation of poor ground or made ground (this usually

manifests itself within the first 10 years of the life of the building, in the form of

progressive damage)

• Movement caused by nearby excavations

• Erosion of fine soil particles due to the passage of water, for example a

leaking drain. This can, over many years, bring about localised subsidence

damage by slowly washing away the fines in the soil, or softening of the

ground

3.3 CAUSES OF STRUCTURAL DEFECTS ASSOCIATED WITH THE STRUCTURE

• Material shrinkage and creep

• Corrosion or decay caused by water ingress / lack of maintenance

• Differential thermal movements in dissimilar materials

• Poor detail design or workmanship

Observed Defects


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March 2011

Page 4

3.4 PLAN OF BUILDINGS

ELEVATION 1 ELEVATION 2

ELEVATION 3

ELEVATION 4

ELEVATION 5

ELEVATION 6

ELEVATION 7 Newer additions to

original building

ELEVATION 8

Observed Defects


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March 2011

Page 5

3.5 ELEVATION 1

Elevation 1 (Old electrical sub-station)

Diagonal crack following mortar line from bottom left to top right of the elevation. Crack

size increasing towards top right suggests differential settlement of building foundations

(crack width reaches a maximum of approx 40-50mm).

The upper side of the crack steps in an outwards direction from the lower wall by up to

15mm in places.

The crack has been re-pointed in the relatively recent past.

The concrete roof ‘overhang’ is in very poor condition – signs of spalling and cracking.

No expansion joints observed.

The green line represents a 10mm step out of the wall. This is the approximate position

of the internal ground floor level.

There are areas of minor cracking and mortar loss over the entire elevation.

Shows a lintel with a ‘blown’ face – loose material to be broken out and

rendered to prevent falling debris.

Observed Defects


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March 2011

Page 6

3.6 ELEVATION 2

Elevation 2

Major vertical cracking and bulging at the top left hand corner of the elevation – this requires immediate attention.

The green line represents a 10mm step out of the wall. This is the approximate position of the internal ground floor

level.


Observed Defects


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March 2011

Page 7

3.7 ELEVATION 3

Elevation 3

There are many minor diagonal cracks throughout the

elevation.

The above photograph shows a vertical crack propagating

up the upper section of the wall and between the concrete

roof panels. This shows the scale of lateral movement that

has taken place. The separation of the roof structure has

inevitably resulted in the ingress of water (which in time will

result in more damage) – this is believed to be true

throughout the main building.


The green line represents a 10mm step out of the wall.

This is the approximate position of the internal ground floor

level.

Observed Defects


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March 2011

Page 8

3.8 ELEVATION 4

Elevation 4

There are minor diagonal cracks throughout the elevation (up to 5mm).

There is an obvious diagonal crack extending from the bottom right of the wall. The crack is relatively consistent along

its length at approx 10mm in thickness. This suggests a lateral ‘shift’ caused by tension in the brickwork. Again,

Inadequate foundations or differential settlement of the foundations are the likely cause.

Observed Defects


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March 2011

Page 9

3.9 ELEVATION 5

Elevation 5

The area of most concern is the lower right hand corner of the elevation between ground level and the door lintel. The

photograph to the right shows how the wall has shifted and rotated. This movement has caused the diagonal crack from the

door lintel.


There is minor cracking throughout the elevation.

25 mm

Observed Defects


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March 2011

Page 10

3.10 ELEVATION 6

Elevation 6

There are several diagonal cracks through the chimney breast and to the left of the

elevation resulting in openings up to approx 10mm.

There are minor diagonal cracks around the window openings which could be due

to inadequate lintels or as a result of general movement/settlement linked to the

foundations.

Mortar loss is present throughout the wall which will lead to further damage in

freeze/thaw conditions etc.

There is minor cracking throughout the elevation.

Observed Defects


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March 2011

Page 11

3.11 ELEVATION 7

Diagonal cracking through infill

panel propagating from

protruding pipe

Diagonal and vertical cracking

from window openings

Diagonal cracking from window

out to corner of building.

Cracking along the top of the

bottom course of brick to

underside of old window cill.

Elevation 7

No major problem was identified on this elevation, only minor to moderate cracking which implies

foundation movement.


Observed Defects


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March 2011

Page 12

3.12 ELEVATION 8

Elevation 8

Large cracks exist above the fire exit doorway (left photograph), above the window to the right of the

doorway (top right photograph) and above the embedded steel beam (above photograph). These are

all signs of foundation movement / rotation.

Minor cracks and mortar loss are present throughout the elevation.

Observed Defects


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March 2011

Page 13

3.13 NEWER ADDITIONS TO ORIGINAL BUILDINGS

Boundary wall forms integral part of

structure. No Damp Proof Course

observed. Damp issues within the

building.

Flat roof appears in poor condition. Felt

seams have de-bonded in areas

resulting in water ingress.

Concrete footings appear to be shallow

leaving them susceptible to settlement

and lateral movement.

Newer additions

Generally the single storey additions have been built

to a very poor standard and/or design.

The brick faced entrance, shown in the photograph to

the right is built into the boundary wall. This boundary

wall is in very poor condition, looks to have little to no

foundations and has no damp proof membrane.

Damp, and problems associated with damp, within the

building is inevitable.

Definite foundation sizes and depths are not known

but assumed to be shallow

Observed Defects


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March 2011

Page 14

3.14 INTERNAL DEFECTS

First floor toilet block, main building

Loose wall tiles throughout and gaps between wall and

false ceiling. Mr. Ahmed informed us that during recent

high winds all ceiling tiles fell down. This indicates high

levels of movement within the roof structure.

Movement of the foundations and dropping of the walls

could have resulted in the roof steels losing

ties/bearing to the walls thus swaying/uplifting under

high wind loading.

Peeling paintwork suggests water ingress.

First floor room, sub-station building

Large cracks between windows in newly plastered

room. These are signs that the differential

settlement/movement of the foundations is

PROGRESSIVE and therefore of great concern.

Single storey addition

Large cracks are present throughout of the internal

walls of the single storey additions. They exist

between adjoining walls and between walls and

ceilings.

First floor, Main building

Evidence of water ingress in the form of water stains

on ceiling tiles.

Internal Defects

Major cracks and evidence of wall movement are present throughout the single storey additions. This supports the

assumption that poor quality shallow foundation are present, and that the additions are tied to the unstable boundary

wall.

In the main building minor cracks and bulges exist throughout. The more major issues are at first floor and ceiling

levels where movement of the roof structure is evident.

Observed Defects


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March 2011

Page 15

3.15 BOUNDARY WALLS

Boundary walls

There are major cracks located around the entire boundary

wall, a selection of them have been shown in the

photographs to the left. All these cracks show sign of

differential settlement i.e. the crack widens/narrows up the

wall as the adjacent wall rotates with the foundation.

There are also areas of ‘blown’ brick faces caused by freeze

thaw action.

Mortar loss is prevalent throughout.

Running repairs have been carried out over a period of time

including re-pointing and the infilling of various doorways

and window openings.

Infill panels have not been tied into the surrounding

brickwork resulting in them falling away.

Further investigations required


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March 2011

Page 16

4. Further investigations required

It is recommended that the following investigations are undertaken to determine

uncertainties identified in this report.

Item Description Budget Cost

1.0 Drainage Survey- to assess the condition of drainage

pipes with a view to identify potential fractures

600.00

2.0 Desktop Study- to determine whether there is potential for

unacceptable ground risk within the site

1,500.00

3.0 Ground Investigation- Hand dug pits to determine the

nature of the foundations and sample boreholes to identify

the soil characteristics.

7,500.00

4.0 Crack Monitoring- Installation of glass tell tails to monitor

the activity of cracks over a 12 months period. It is

suggested the tell tails are installed after a firm diagnosis

has been made.

2,500.00

5.0 Full roof survey – this will include inspection from above

(requiring access), and also an inspection from below by

removing sections of the false ceilings (especially in steel

beam bearing locations and areas where major cracking is

visible from outside i.e. Elevation 2)

1,200.00

Recommendations


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March 2011

Page 17

5. Recommendations

Subject to the findings from further investigations listed in section 4, it is considered

the following remedial works will be necessary to strengthen the structural stability of

the building.

Item Description Cost (£)

1.0 ‘Stitching’ - Use helical bars for crack stitching masonry

repairs and brickwork reinforcement of cracked walls. By

stitching wall cracks and lintels, masonry walls are stabilised

and structural integrity is restored. This would be

recommended in all areas with major cracks.

8,000.00

2.0 Breaking out and replacing sections of walls – this is for

areas of extensive damage, including leaning or bulging

walls, or where there’s loss of bearing below beams

10,000.00

3.0 It is recommended that the boundary wall is reduced in

height to limit the progression of settlement/rotation. In the

long term it is advisable that the wall is taken down and

rebuilt on adequate foundations

8,000.00

4.0 Underpinning – this could be carried out using mass

concrete or mini piles. This is an expensive option and risks

further damage during installation

100,000.00

5.0 Roof repairs / rebuild – the extent of the work needed to the

roof will become clear after further investigations

5,000.00

6.0 Some areas of brick may need breaking out and replacing

(areas where major cracking is occurring such as those

identified on Elevation 2)

3,000.00

Budget Cost £134,000.00

nba structural survey

Documents

site survey

visual structural survey

causes of structural

intrusive survey

major defects roof survey

site location

internal defects

serious defects