lintel supporting rafters

Apr 16, 2009 6 Replies

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sm_jamieson 17 years ago

I need to lintel over a 1200mm wide window (cavity wall), with roof rafter ends supported only

1 or 2 brick courses above this, and standard catnic-style lintels are
3 brick courses high I understand. Can you get such lintels with less rise in the box section ? Or will I need to use something different, like a separate RSJ lintel in each leaf ?

Also, since there's not many brick courses over the lintel to the rafters, would a box lintel be able to cope with slight point loads that may result ?

Thanks, Simon.

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Kipper at sea 17 years ago

Not quite sure what height you want to reach or if you intend fixing the rafters to the lintel. Various heights can be obtained by using RSJ with timber bolted to the RSJ and the rafters spiked to the timber

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Roger Mills 17 years ago

What not just use a cavity wall lintel, like the one shown at

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doesn't have a box as such, but just has a platform for each skin, and a triangulated part which goes inside the cavity. For a span of 1200, the bit inside the cavity won't be more than two brick courses high.

It should be ok with a wooden wall-plate above the brickwork - presumably on the inner skin - with the rafters nailed to that. If you're worried about point loads, use a couple of courses of blue engineering bricks under the wall-plate.

Have you discussed it with your local Building Control department? They are usually quite helpful.

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Phil L 17 years ago

You can get shallower lintels than 3 courses, and they don't have to be catnic style

Yes, they are made to cope with possibly a three or four storey building above them, so a joist or two and associated tiles are nothing in comparison.

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sm_jamieson 17 years ago

Yep its the point loads. But it will be aircrete blocks anyway. As long as a wooden walllate (2x4 on its side I guess) is in place this will spread the weight quite well. I've never done a roof before - can you tell ?!

Cheers, Simon.

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sm_jamieson 17 years ago

Yep prob a couple of courses plus wallplate inside. Its a question of keeping the roof pitch as close to 12.5 degrees as possible for the redland regent tiles. I'll put a double layer of impermeable membrane under the tiles just in case. As long as BCO doesnt put a dodgy device on the roof after and say, ooh, 11.9 degrees, pull it down ! Simon.

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Phil L 17 years ago

The first time I seen a pressed steel lintel I thought, 'that's not strong enough', but having sen them used over 10ft openings, I changed my mind - a

1.2m is tiny really, and the wallplate covers the full length of the wall, and don't forget about displacement - each joist isn't bearing directly downwards onto the plate and thereby the lintel below, it's wight is displaced sideways onto the remainder of the blockwork

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