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Extensions

Advice please - my builder installed a lintel that was too big

Chris 31/07/2026 - 7.51 AM

So I had a ground floor extension, the builder built the cavity walls with 100ml cavity, should have been 150. He still ordered a 150ml lintel so it overhanged slightly on one side and building control wont' sign it off. Any options other than rebuild the wall/replace the lintel?

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4 Answers

ADR Property Maintenance

Rating: 5 out of 5
Boston
Cut the lintel down
Answered31 July 2026
1

Mansarda Ltd

Rating: 4.9 out of 5
New Southgate, London
An engineer could inspect the installation and provide calculations/details showing that the lintel is adequately supported and that the eccentricity/overhang is acceptable. This is probably the first thing I’d investigate before touching the wall. Good luck.
Answered31 July 2026
1

Fix-it Maintenance Guy

Rating: 4 out of 5
Wembley
If that was specified on the drawing 150mm cavity and the builder chose to do it only 100mm there is nothing you can do as the building control won't sign it. Changing the lintel doesn't mean you follow the drawing which mean is out of scope. If the cavity was 100mm you just need another lintel or try to cut the existing one which again won't be acceptable.
Answered31 July 2026
1

Anonymous user

No real alternative, unfortunately. If Building Control has rejected it, the correct lintel needs to be installed. As it’s the builder’s error, they should replace it at their own expense. I’d also ask Building Control if they’ll accept an engineer’s design, but in most cases replacing the lintel is the proper solution.
Answered31 July 2026
1