Lintel detail for door opening to support flat roof joists

10 Jul 2022
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United Kingdom

I am looking for the best solution to span across 2400mm doors, supporting roof joists.

The building is governed by height, and I am already too high so ideally want a solution where I won’t need a wacking great box section or concrete lintel with joists supported on top. I need 150mm bearing so looking at 2700mm lintel.

I found a Keystone SB/K solution which I thought was great, I would support the joists off of the ‘inside’ of the L-shape with insulation between joists…

However, their technical guidance suggests I must include a 150mm or 2 courses of brick on top of the flange before then loading on top of that. I’m struggling to understand how I can’t just load directly onto the flange itself without the need to introduce the additional weight of masonry. I understand this is now a point load and not a UDL but I am only supporting a simple flat roof.

The alternative might be to use a box section, such as the HD BOX/K, with some sort of a hanger arangement but I am not sure if this is possible, how I would mechanically fix hangers and ensure I don’t get rotation of the section under loading.

I’ve attached some images for reference…

Any help / advice would be appreciated.


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Is the wall over the door a cavity wall or just single skin?
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It's the same as trimming around a chimney breast or staircase.
Okay, not familiar but I think I see the logic. At this stage I am just trying to do the design before I engage contractors / order materials. I assume you just use standard joist hangers?

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