CROSS Safety Report
Adapted masonry support props
This report is over 2 years old
A reporter has come across adapted masonry support props in use and in their view, they must only be used in the case of limited openings where the masonry can arch over.
Key Learning Outcomes
For the construction team:
Temporary supports should be used in accordance with the manufacturer's guidelines (where these exist), and should be checked and signed off on installation
Having a competent temporary works designer/adviser in place to supply an engineered solution can ensure all temporary works are carefully considered and planned
Props should not be adapted without formal agreement of the appropriate responsible person on site
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In report 32 it was asked if other engineers have had any contact with a modified dead shore popular with builders.
A reporter has come across these in use and in their view, they must only be used in the case of limited openings where the masonry can arch over leaving only a small area of masonry below the arching that can potentially break away. These shores, in their opinion, are usually adequate and indeed useful to support this small triangular area of masonry to limit the making good that would otherwise be necessary if all the masonry were removed.
However, there are safety issues, especially where they are used unsupervised or by inexperienced builders. There must obviously be a sufficient number of them to support the weight of the masonry referred to, but this may be underestimated in large openings or other cases where arching may not take place. Another issue is that the eccentricity implies a horizontal force at the foot of the shore (it should not be installed out of plumb to compensate – another bad idea).
However, there are safety issues, especially where they are used unsupervised or by inexperienced builders
The horizontal load may be resisted by friction and the impression gained that all is well but an accidental knock in the right direction could collapse the prop as the bottom skids out. Where there is doubt the reporter would advise fixing down the foot to whatever base (presumably substantial) that exists or placing a horizontal brace to the foot (which might form a trip hazard and need to be protected).
All in all, these are for light use only and never for heavy shoring. The reporter thinks that the manufacturers, and possibly the hire companies, would be negligent if they did not provide some guidance on the use of such props.
Expert Panel Comments
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Correct propping is essential and temporary works failures are a recurrent theme in collapses on site. It appears that this type of prop should only be used in specific low risk circumstances which have been examined by a competent person.
Temporary supports must be used in accordance with the manufacturer's guidelines (where these exist), should be checked and signed off on installation, and should not be adapted without formal agreement of the appropriate responsible person on site.
The Health and Safety Executive (HSE) has plans for a refurbishment safety initiative in view of the many safety problems encountered in this type of work, e.g. ensuring general interim stability of the building structure, and CROSS will be apprised of progress.
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