CROSS Safety Report
Excessive surcharge at the back of a retaining wall
Overview
A reporter raises concerns about excessive surcharging at the top of a small retaining wall which was supporting the garden of the property.
Key Learning Outcomes
For contractors:
- Note that there have been numerous failures associated with freestanding and retaining masonry walls with serious consequences. A previous Alert was issued by the Standing Committee on Structural Safety (SCOSS) –Preventing the collapse of freestanding masonry walls.
- Be aware that any works that may affect the loading of existing retaining walls should be assessed by a suitably qualified and experienced structural or civil engineer
Full Report
Find out more about the Full Report
The Full Report below has been submitted to CROSS and describes the reporter’s experience. The text has been edited for clarity and to ensure anonymity and confidentiality by removing any identifiable details. If you would like to know more about our secure reporting process or submit a report yourself, please visit the reporting to CROSS-UK page.
This concerns a house renovation project where the contractor had placed a significant quantity of materials on pallets at the top of a small retaining wall. The wall was supporting the garden of the property. There was a narrow public footpath separating the wall from a busy B road.
The retaining wall was approximately 1.1m high, two bricks thick, over 50 years old, and leaning outwards by 10-15mm. The reporter believes there were possible gas services running from the footpath up the wall and under the garden towards the property.
The reporter estimated that the surcharge from a two-storey stack of pallets of brick could be well in excess of a) HA loading: 10kN/m2 or b) HB loading 45 units: 20 kN/m2. There was a clear risk of failure due to the contractor having not considered the implications of pacing substantial loads at the top of an inadequate retaining wall.
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Expert Panel Comments
Expert Panels comment on the reports we receive. They use their experience to help you understand what can be learned from the reports. If you would like to know more, please visit the CROSS-UK Expert Panels page.
As is so often said by CROSS - old masonry retaining walls can be dangerous. Any works that may affect the loading of these walls should be assessed by a suitably qualified and experienced structural or civil engineer.
Overloaded masonry retaining walls are liable to sudden failure even in domestic circumstances with serious, and sometimes, fatal consequences. The danger increases with surcharge loading at the top of them.
Note that there have been numerous failures associated with freestanding and retaining masonry walls with serious consequences. A previous Alert was issued by the Standing Committee on Structural Safety (SCOSS) –Preventing the collapse of freestanding masonry walls.