lintel padstones into cavity wall

11 Apr 2006
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United Kingdom
I'm considering opening out an old doorway by ~15 cm either side. The existing lintels aren't long enough so I'll need to replace them. This isn't an issue on the side where they can simply fit deeper into the existing wall, but on the other side I'd just be left with a cavity wall running at a right angle. The nearest leaf is only 100mm thick, so in this situation am I requried to leave a 50mm pier, or can I extend the lintel into the second leaf? Or perhaps lay a padstone over both leafs beheath the lintel?

In the diagram below, my problem is with the bottom lintel, left hand side.


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Allowing it to breach the cavity will create a cold bridge so that's a bit of a no-no. It'll be fine with a 100mm anyway but it will really depend on how much of a stickler your inspector is, as he'll have the final say-so anyway.
100mm bearing onto the inner leaf should be fine. If you do have a stickler of a BCO you could also look at removing the bricks beneath the end of the lintel and cutting the lintel you're taking out down to say 400 mm (2 bricks) and use it as a padstone beneath the new lintel, running along the existing wall. This will increase the bearing area and give the equivalent (or more) of a 100mm wide lintel with 150mm bearing length. Shouldn't cost you any more.
Okay cheers guys. I'd assumed you always needed a 150mm bearing area at either end - perhaps that's because I've been looking at steel box lintels - is that OTT for this application, and I should use concrete reinforced?

Sounds like I need to leave it up to the BCO then I guess!
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The 150mm bearing is when the wall is in line with the lintel, 100mm bearings into perpendicular walls are the norm (you get better load spread etc).

Padstones beneath the lintel is probably an overkill (unless you have real weak blocks or massive direct load over).

Size of lintel always depends on whats above it.. :)

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