Widening a lintel

16 Jul 2008
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Hi there,

As part of my house renovation, I'm replacing a floor-length 800mm wide window (god knows why they put that in) for a conventional height 1200mm window. So of course the existing lintel needs widening. Don't worry, I'll be acro and strongboying above before the work. Just have a question about the lintel...

Existing lintel is a massive concrete thing that spans the whole width of the cavity wall. Can't seem to see these available on the merchants sites, and seems a bit excessive too. I did see a detail drawing on Travis P's site showing two 100mm concrete lintels - 1 for each leaf of the cavity wall. This seems the easiest and cheapest solution, but can anyone confirm if that's the done thing? Otherwise looks like a catnic or similar and some bricks. For information, it's a bungalow but this is a gable wall. A pretty shallow pitch roof (it's an extension) so not a huge amount of weight above this lintel, but plenty I guess.

Any help appreciated,

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i would be inclined to use a proprietary pressed steel type lintel i.e. catnic, i.g. or similar.

you will need to know the cavity size when buying the lintel. just as cavities have increased in size, so have lintels to suit. 50mm, 75mm and 100mm are the norm, with 100mm being the most recent.

potentially you could use concrete p.c.c. lintels but these look ugly from the outside.

...or use a p.c.c. lintel internally and angle steel externally.

the fist option is still the best and least likely to be a problem.
Thanks for the heads up on cavity sizes! Mine are pretty narrow, in fact almost non existent in one part of this old extension I have already had cause to reveal.

I forgot to mention, the building is rendered and painted, and I'll have to re-do this where I alter the lintel - so not too bothered about a concrete lintel being visible.


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Have you thought about the tray above the window?
Combined box section lintels (eg. Catnic) incorporate this into their design, don't forget weep holes if rendering.
If you have one solid concrete lintel at the moment I am surprised you don't have a damp problem around the window (unless it is a sheltered wall).
the fitting a cavity tray (or should i say the retro-fitting) is not enforced in all council authorities.

this is because the conditions that lead to the necessity of a tray occur very seldom in most inland areas.

to build them in whilst constructing a new extension or house makes for precautionary common sense.

i have only witnessed one occasion where a cavity tray would have been useful. this was due to wind driven rain, over poorly pointed brickwork over a sustained and prolonged period of time.

i for one will not lose any sleep knowing there are no cavity trays in my building.
Fair enough, I live on the Isle of Wight where they are common place in new build and often retro fitted to older properties - don't know if enforced in new build though. Never realised there were such differences geographically.

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