Contract administration of building works on several blocks of flats
Allcott Commercial’s team includes experienced chartered RICS surveyors and ICE/IStructE structural engineers who specialise in contract administration.
Brief: The brief had two parts. Firstly, we were asked to carry out specific structural investigations to investigate cracking of several quoins in a large flat and terrace housing complex. Secondly we were instructed to manage the associated building works that were required to rectify the defects.
Property: Five-storey blocks of flats and adjacent terraced houses in Banbury, Oxfordshire. The properties were constructed in 270 mm wide cavity brickwork beneath multi-pitched roofs with concrete tile covering.
Instructed by: Property management company.
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Initial structural investigation
- We found significant movement of the walls of the blocks of flats.
- In some areas, the quoins had separated from the main walls by up to 40 mm.
- We carried out a high-level inspection and found that the wall had moved substantially. Looking down the cavity, our structural engineer could not detect any ties from the quoin to the main body of the property.
- We took some brickwork down and noted that the blockwork on the inner skin was in a very poor condition. This was due to the movement that had caused the lower block to shear and move vertically.
- We made similar observations at the other gables that were included in the inspection.
- We concluded that the movement of the quoins was caused by the diagonal force of the extremely heavy copings that were laid on the diagonal brick courses. These were exerting a diagonal force down the slope, against the quoin.
- The absence of ties between the quoin and the main body of the property created a plane of weakness. Consequently, the quoin was being pushed over.
- We advised that the best way to rectify the area would be to demolish the corners that were affected, down to the top of the lower quoin. They should then be rebuilt by installing a bricktor bed reinforcement across the joint of each brick course.
- Whilst the copings could potentially be reinstalled, because it should be possible to salvage them, we recommended installing a lighter capping system of a proprietary aluminium profiled section instead. This would reduce weight and prevent sliding down the diagonal areas.
- Allcott Commercial was instructed to carry out contract administration of the building works.
- The properties were constructed fairly recently, and so the costs were covered by the NHBC scheme.
- We carried out regular site inspections to monitor progress. We produced photographic reports to record the building status and update our client.
- Points of note included:
- ensuring that appropriate precautions were in place to protect the exposed parapet and flashing at the junction with the slate roof covering, once it had been exposed
- continuously assessing the quality of the previous works as demolition progressed and revealed more brickwork
- checking that all operatives were wearing appropriate PPE
- ensuring that scaffolding had been inspected by a CDM consultant
- assessing the security of the site.
- There were some delays to the project because the extent of the rebuild was continuously reassessed as more of the building works became exposed. We continuously evaluated the project status and any impact it might have on the overall cost of the project.
- The project was completed successfully and costs covered by the NHBC scheme.
- Since completion, similar defects have been identified on adjacent blocks of flats. Allcott Commercial has been instructed as contract administrators for the additional works on the adjacent blocks.
Read more about our contract administration work here.