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CROSS Safety Report

Masonry support prop adaptor

Report ID: 32 Published: 1 July 2006 Region: CROSS-UK

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Overview

A reporter has written to say that when carrying out temporary needling and propping of openings formed in masonry walls one of the most important aspects is to ensure that the props are concentrically loaded and plumb.

Key Learning Outcomes

For construction professionals:

  • Any device that modifies the behaviour of props by introducing bending moments is potentially hazardous and should be reviewed by an experienced engineer before being used

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A reporter has written to say that when carrying out temporary needling and propping of openings formed in masonry walls one of the most important aspects is to ensure that the props are concentrically loaded and plumb.

BS 5975:1996 gives safe working loads on adjustable steel props that are plumb within 1.5 degrees (i.e. not exceeding 25mm out-of-vertical over a height of 1m) and with no eccentricity in excess of 25mm. The use of a steel bracket on top of the prop, giving an eccentricity of about 200 mm would not seem to be such a good idea.

Interestingly such a product does exist and, says the reporter, has proved very popular with builders who see the advantage of propping only one side of a wall. The prop is hired from builders’ merchants with minimal safety instruction.

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An extract from a leaflet enclosed with the report is:

“Maximum load bearing capacity 340kg (750 lb) per unit
Maximum safe working height is 3m from a firm base
Designed as a cost effective labour saving device.
It will fit any adjustable steel builders’ prop with a 6” or 150mm square top plate.”

There is a sketch showing a plate on top of an adjustable prop with an angled brace going back to the prop. The prop is situated outside the wall face of a lintel and the eccentricity from any loading on the prop would be considerable.

The reporter is concerned about the prop being potentially unsafe due to bending moments being introduced by this product into props designed for axial compression. The quoted maximum safe working load (340kg) is considerably less than that for a 3m prop loaded according to the BS but any device that modifies the behaviour of props by introducing bending moments is potentially hazardous and should be reviewed by an experienced engineer before being used. Do other engineers have experience of similar products?

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