31 Dec 2020
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United Kingdom
Hi, I am building a single story extension with a lean to roof , I am constraint with height of the front wall of the extension because of upstairs windows to give 15 degrees roof pitch, with a French door in the front wall of the extension of 2mtr high, and a cantic type eaves lintel over that, my question is what is the minimum amount of bricks on the inner wall over the lintel is required, I cant find any information on this, with two bricks and a 50mm wallplate I can get 15 degrees pitch on the roof with a 150mm rafter birdmouth down to 100mm, is that OK.
regards Andy.
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is that OK.
regards Andy.

Composite lintels can take point loads but are usually three (brick) courses deep in any case. A lot depends on the span, i.e. the width of the patio door set. If the roof is such that an external lintel is not required, why not look at using say a 152mm deep steel beam with the plate fixed directly on top?
Thanks for the info, yes that is a possibility, it would bring the height under what I need, although I would need to get a structural engineers report for that I suspect, unless one of the lintel companies sell them with all the info already worked out. The span is 1.8m.
The span is 1.8m.
You may be able to use a 150mm deep box lintel for that as long as the roof load is factored in. A lot depends how shallow the roof is and the need to (possibly) show masonry on the outside courses. A steeper roof would almost certainly return back with the soffit level with the tops of the doors - thus alleviating the need for external support.

We normally mock-up a rafter to the correct pitch and see how the soffit works and whether we need to lintel the outside (or not).
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Why not consider a timber beam, such as two 150 x 50 screwed together - easily do over a 1.8m span carrying only a roof.
Why assume it's got to be steel on such a short span?
Also easy to fix plasterboard, and noggins for fascia and soffit.
That seems to be the way forward, the total width of the extension is 8mtr wide, I could use 4 * 4.2m lengths of 150X50 bolted together and staggered to form a lap joint in the middle as there is a 1.8m window on that wall as well, this would form the wallplate and lintel .
this is as far as i have got with the job


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yes I know, first time I've done any building, it wont be seen when its rendered.

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