CROSS Safety Report
Building control and the design of a free-standing wall
This report is over 2 years old
A reporter raises concerns over the design of a 2m high freestanding garden wall.
Key Learning Outcomes
For civil and 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
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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.
A client wanted a garden wall 2m high, and a reporter referred to the OPDM leaflet which states that for the region in question the height of a freestanding wall should be brick 328mm thick to resist wind loads. The reporter therefore recommended that a 328mm brick wall should be built, but the client appointed another engineer who obtained approval for a wall of 140 block + 103 brick (i.e. 243 thick).
The reporter advised building control in the city of the situation and asked them to produce calculations to justify the design which they declined to do. The reporter believes that building control engineers have an obligation to comply with guidance, both on the grounds of individual integrity and public protection.
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This report refers to the ODPM leaflet which can be downloaded from the websites of many councils, though oddly not from any government website, as far as I can tell. This leaflet refers to two BRE Good Building Guides (13 and 14), which provide much more detailed advice on the topic than the ODPM leaflet. There are in fact several BRE Good Building Guides and Good Repair Guides about freestanding walls that will be of interest to a professional readership, as opposed to the householder, who the ODPM leaflet is aimed at: GBG 13 Surveying brick or blockwork freestanding walls (1992) GBG 14 Building simple plan brick or blockwork freestanding walls (1994) GBG 17 Freestanding brick walls - repairs to copings and cappings (1993) GRG 28 Repairing brick and block freestanding walls (2000) This can be purchased through www.brebookshop.com. Nick Clarke IHS BRE Press, Garston, Watford WD25 9XX 01923 664170 GBG 13
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.
CROSS has reported numerous cases of collapsed walls including cases where they have caused death. The cumulative evidence is that many walls are not designed to proper standards but there is no requirement for these types of boundary walls to be compliant with building regulations if they do not form part of a building. Nevertheless, there is good guidance available to meet a duty of care for example in the DCLG advice mentioned by the reporter.