CROSS Safety Report
Dangerous substitution of lintels on domestic projects
This report is over 2 years old
This report highlights the structural risk of substituting lintels during domestic projects without approval from the design engineer.
It shows how problems can occur if assumptions are made between design and build.
It demonstrates how good communication within a project team can help to mitigate risk.
Key Learning Outcomes
For construction professionals:
Talk to the design team and regularly discuss your use of products, components and materials
Consider introducing a quality assurance process that covers the correct use of products, components, and materials
Be aware that you could be liable for any damage caused by substitutions
Substitution of construction elements and materials should not be made without design team verification
For civil and structural design engineers:
Share your knowledge of the behaviour of products, components and materials. Tools like span and load tables could be helpful to do this.
Routinely raise the risks associated with substitutions to contractors and the wider project team
During site inspections if construction elements are covered up, consider seeking verification of correct installation from the contractor by means of site photos or paperwork
Find out more about the Full Report
The Full Report below has been submitted to CROSS and describes the reporter’s experience. The text has been edited for clarity and to ensure anonymity and confidentiality by removing any identifiable details. If you would like to know more about our secure reporting process or submit a report yourself, please visit the reporting to CROSS-UK page.
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.
Gaps in the contractor’s knowledge
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.
Issues with identifying lintels
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.
Three safety concerns raised
This situation has left the reporter concerned because:
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.
The lack of identifying marks on the lintels means that it is not possible to determine the capacity of proprietary lintels post-installation, and
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 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
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This is a very common type of issue that occurs on domestic projects. Builders very often substitute components that are different to those specified on the drawings. A typical example in my experience is joist hangers. They seem to think that a joist hanger is just a joist hanger with no regard or understanding of the reason why a particular type is specified. When questioned the reply tends to be "that's just what they had at the builders merchants". Or they say that they have definitely installed the type specified when very clearly they haven't.
Expert Panel Comments
Expert Panels comment on the reports we receive. They use their experience to help you understand what can be learned from the reports. If you would like to know more, please visit the CROSS-UK Expert Panels page.
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.
Unauthorised design change
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.
Verifying what was built matches the design
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.