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219 Deficiencies on access scaffold

Report ID: 219

Published: Newsletter No 22 - April 2011

Report Overview

Investigation by a reporter’s firm into an access scaffold on a refurbishment contract on a city centre site brought to light a number of deficiencies which rendered the scaffold outwith its design parameters.

Report Content

Investigation by a reporter’s firm into an access scaffold on a refurbishment contract on a city centre site brought to light a number of deficiencies which rendered the scaffold outwith its design parameters. The system was further compromised in that the basic components were a system scaffold, but the various add-ons made it a designed scaffold requiring more careful input and proper calculations prepared by and approved by competent personnel. Such records were lacking.

Many scaffolds are designed such that only a certain number of levels may be loaded at any one time. The original brief must be clear on this. This particular scaffold had a number of lifts which could be, and were being, loaded concurrently. There were no barriers in use to prevent this. The hoist had defined anchorage loads which needed to be taken to a sound anchorage. This was not the case with the ties stopping in the middle of the scaffold with no enhanced bracing to dissipate the loads. There was a staggered base level necessitating three legs to extend below the general level. Two of those legs were consequently braced in one plane only giving rise to the possibility of lateral failure. The existing façade was an ashlar stone fixed to a sub frame. To prevent damage to the stone tie centres had been extended beyond that necessary to restrain the scaffold.

In conclusion, says the reporter, it is apparent that the following should have taken place and been recorded. This in essence would follow the requirements for a temporary works coordinator.

  • A clear brief defining the particular use and all loads required to be resisted should be prepared.
  • A competent designer should be appointed to design and detail a scheme which should be checked before being passed to the user. The drawing should note loading requirements and any special points.
  • Many sites will require a visit by the designer to confirm that his assumptions are correct and workable.
  • The user should confirm that the points in his brief have been fully addressed.
  • The drawings and calculations should be readily available on site.
  • The scaffolder (suitably qualified for the type of scaffold) should erect to the drawing and sign off as complete and safe to use. Note: The handover certificate should clearly reference the design drawing and where applicable pull out/ proof tests of any ties should be attached.
  • Any modifications should be confirmed in writing and drawing form by the designer.
  • The scaffolder should put these into place and sign off and re issue an updated handover certificate
  • As a minimum, weekly checks should be made in conjunction with the design drawing requirements and signed off by a person competent in the type of scaffold.

Comments

Scaffolds are often critical structures in their own right which need careful design to established standards (e.g. TG20.08 and Eurocodes). These standards should relate to the whole life of the structure as alluded to in the report. Collapses such as that in Milton Keynes in 2006 give emphasis to this essential care and attention. Historically there may have been many scaffolding failures due to lack of restraint from the main building. Casual observation on any site will also reveal that loading due to stacked materials can be significant and highly variable. This report reinforces the view that competent robust design is required just as much for temporary works, as it is for main structures. Moreover, a sensible safety precaution might be for temporary works designers to visit sites and vet that their designs have been built in accordance with design assumptions unless this task is covered by the Temporary Works Co-ordinator. In addition, the duty of care on a professional engineer for the main works would oblige him to make comment to the contractor should inadequate use or design of temporary works be suspected.


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