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CROSS Safety Report

Stability of brick walls

Report ID: 475 Published: 1 April 2015 Region: CROSS-UK

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Overview

A 230mm cantilevered brick wall approximately 1.6m high failed after backfill material was placed behind it, which was not the design intent. 

Key Learning Outcomes

For construction professionals:

  • Be aware that backfilling small gaps can generate enough pressure to destabilise walls as demonstrated in this report

  • There has been numerous failures associated with freestanding masonry walls and a previous Alert was issued by the Standing Committee on Structural Safety (SCOSS) – Preventing the collapse of freestanding masonry walls

For structural design engineers:

  • Careful consideration is required for the design of cantilevered brick walls, particularly in the temporary stage because there is no redundancy and relatively small loads at the tip can precipitate failure

  • Consider what reasonably foreseeable loads could be applied beyond the code minimum values on elements such as freestanding walls

Full Report

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A 230mm cantilevered brick wall approximately 1.6m high was built roughly 300 to 400mm in front of a rock face. The space between the wall and rock face was backfilled (which was not the design intent) and it pushed the wall over.

It was surprising that so little soil could generate sufficient pressure to topple the wall. However, the backfill was recently excavated clay that expanded after placement and created pressure between the rock and the wall.

Expert Panel Comments

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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.

The water pressure generated in a 100mm gap is just the same as if the gap were 1 km. If the designer of the wall was aware of its location it would be a reasonable expectation that he/she would highlight the risk of backfilling.

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