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889 Dangerous substitution of lintels on domestic projects

Report ID: 889

Published: Newsletter 58 - April 2020

Report Overview

A contractor was unaware that a substituted lintel did not have the same structural properties as the specified lintel.

Report Content

New lintels were being installed as part of a home extension project. The structural engineer had specified the concrete lintels. However, during construction, the contractor informed the engineer of their intent to substitute the specified lintel with an alternative lintel from the same supplier.

It was the contractor’s understanding that the structural properties of the two lintels were identical because the geometry was identical. The engineer disputed this claim and used span/load tables to show the contractor that, for the required span, the capacity of the alternative lintel was approximately 0.7 times the capacity of the specified lintel. The contractor admitted that they were unaware of this and had been substituting these lintels for several years on the recommendation of the supplier.

The engineer later learned that the supplier spray painted the end of one type of lintel to allow it to be identified from the other type, but the reporter points out that this does not assist with identification of the type of lintel after it has been installed.

This situation has left the reporter concerned because:

  1. The contractor and their supplier’s lack of understanding means that several understrength lintels have been installed on other projects, eroding safety factors and significantly increasing the risk of failure;
  2. The lack of identifying marks on the lintels means that it is not possible to determine the capacity of proprietary lintels post-installation, and
  3. The fact that the contractor could install understrength lintels for several years without challenge highlights a systematic error in the control of product substitutions in domestic projects.


The topic of inappropriate substitution has been raised in other published reports. A common case is substitution without reference to the design team, which runs the risk of undermining design intent. If anything went wrong, and no reference to the design team had been made, the person or organisation making the change might be liable.

No changes should be made without design team verification. In this case, lintels might be considered minor items, but in any wider study of disasters, it will be found that ‘unauthorised design change’ is a common heading for disaster cause.

A second issue is the very common one of being able to verify that what was built matches design intent. Sometimes this cannot be done because items are covered up. Sometimes without markings (or paperwork), verification is equally impossible. All this points to the need for a proper quality assurance and inspection regime.


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