CROSS Safety Report
Failed two storey retaining wall
This report is over 2 years old
A two storey high retaining wall adjacent to a house collapsed.
Key Learning Outcomes
For the construction team:
All retaining walls can be dangerous and should be designed by a suitably competent engineer unless the walls follow the empirical proportions and conditions illustrated in Approved Document A of the building regulations
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A developer built a small estate adjacent to an existing property with a retaining wall between the two. The reporter checked the proposal on behalf of the owner and told the developer that it was not safe and would be dangerous. The builder took no notice so the reporter called the local council who refused to get involved and the wall was built.
It was constructed of concrete blocks, was almost two storeys high, and had no reinforcement. Melting snow seems to have been too much for the wall which collapsed moments after someone from the adjoining property had walked past (Figure 1). The wall fell onto the adjacent property and cracked the end walls, and there is the possibility of further collapse as the surrounding ground is now unstable.
Expert Panel Comments
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A major concern hereto has been that building control has no duty to look at such structures, yet from the many reports sent to CROSS retaining wall failures are common and some are deadly. Examples are seen of completely unsuitable designs and this is one of them. There have been attempts to change the situation but so far without success.
All retaining walls can be dangerous and perhaps should be designed by a competent structural engineer unless the walls follow the empirical proportions and conditions illustrated in Approved Document A of the Building Regulations. A call to the Health and Safety Executive might help as this does fall within their remit, but any action may be resource constrained.
In the longer term education is part of the answer, but as commercial gains from building irresponsibly may be substantial, these examples are likely to continue. This trait of builders, or anyone else, ignoring professional advice is worrying as it appears to be becoming much more widespread. Retaining walls clearly remain a significant issue that requires vigilance.
This report has been re-published to clarify the Key Learning Outcomes regarding the design of masonry walls.
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