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CROSS Safety Report

Substitution of undersize steel sections

Report ID: 369 Published: 1 October 2013 Region: CROSS-UK

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Overview

A reporter feels it is necessary to report a similar but more basic problem on the failure of certified steel products.

Key Learning Outcomes

For the construction team:

  • Substitution of construction elements, for a smaller section size, should not be made without approval from the design engineer

  • Consider introducing a quality assurance process that covers the correct use of products, components, and materials on site

For civil and structural design engineers:

  • Share your knowledge of the behaviour of products, components, and materials
  • Routinely raise the risks associated with substitutions to contractors and the wider project team

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Having read your recent warning on the failure of certified steel products in Newsletter 29, despite having certification, a reporter feels it necessary to report a similar but more basic problem. Given the continuance of the recession their firm are seeing an increased use of smaller than specified steel sections in domestic construction.

For example, a 203 x 203 x 60 UC might be specified on a drawing by an engineer and a 203 x 203 x 46 UC appears on inspection of the installation. Occasionally the correct size is even shown on the delivery ticket. On other occasions the builder has made a decision that the steel is over designed and reduces it without consultation.

This is now occurring on applications in one city at the rate of once or twice a week. The reporter has checked with colleagues in other cities and a similar picture is emerging. This is not a new problem, but it is on the increase. The reporter and his colleagues are giving builders a list of the dimensions of common section sizes and advising them to check their steel before installation. This has the effect of both helping and warning at the same time.

Expert Panel Comments

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This is a serious matter particularly if the substitution of undersized sections is deliberate. The report implies the changes are made to save money for the builder rather than because the specified section is not immediately available. The supply of steel sections is generally well controlled from the steel manufacturer through the stockholder to the steelwork contactor and from there to site.

A builder, or fabricator, who substitutes a smaller size, is likely to be in breach of contract (or worse) and may leave himself open to prosecution should anyone be harmed in the event of a collapse. Changing member sizes is potentially dangerous and extremely foolish. On one site a fatality during erection occurred because the wrong grade of bolt steel had been used.

It is not possible to distinguish one grade of steel from another just by looking. It is not easy to tell one serial size of beam from another since flange and web thickness variations can be small. Clients including most domestic building owners should employ reputable builders and ideally steelwork contractors with certified quality management systems to ISO 9001 in place.

The builder/steelwork contractor should also have a system in place to check the steel arriving onsite – e.g. checking the delivery note against the order, the original specification and the inspection document. This is part of CE Marking and is embedded in the factory production control system.

The majority of steel sections usually arrive with the part number marked on the section (hard stamp or stencilled on) to aid identification. Designers should always be involved at the construction stage but on domestic projects this can be difficult. Small builders and fabricators must be made aware of the importance of using correct section sizes.

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