Block masonry support over flat roof corner steel/lintel detail

[PhilC]

Hi Everyone,

 

I am in a bit of a puzzle about how to detail the steelwork to support a 100mm block (rendered) wall (~2.5m height lightweight block).

 

I could put the timber frame lintel or steel beam to carry the external block leaf lower down closer to the main beam but this creates a large thermal bridge in my mind, between the timber frame panel and the flat roof insulation. Raising the lintels up allows the PIR to come in underneath and prevent the thermal bridge. I did speak with my SE about it and in principle he thought this was ok.

 

 

PIR of flat roof can come up to the frame under the masonry external leaf. Weather tightness, cavity tray etc would be above this to run out to the roof deck.

 

 

The alternative is to bring the blockwork down to the steel, although this is an issue because the steel is 254mm high as are the metal web joists in the floor, so it takes the full-height plasterboard to T&G deck of the floor level so I cannot have a flat plate weld on it and as said, this seems to create a large thermal bridge even if the cavity is packed out with insulation below the cavity tray.

 

I appreciate thoughts on this one, seems right to try to bring the flat roof insulation under and up to the frame.

 

Render board is an option I guess but I went that route when planning our new 1st floor renovation rather than a new build, it seemed very expensive for the material and work and I think it may be difficult to match up with a rendered block ground floor. Also, I had virtually no interest in quoting for it, part of the reasoning for switching to a new build.

 

Thanks.

 

 

 

[George]

Think I'd rather the simpler solution. Small thermal bridges can be mitigated with internal insulation or lowering the beam a little.