Overthinking flat roof joists/wall junction preserving airtightness

[Olf]

Because on the existing building side there will be an RSJ with infilled bearers and joist hangers attached, I went to replicate the same on the new wall side. That would give me an advantage of easier to maintain continuity of airtight layer (turquise on the drawing) - but looks a bit dodgy, especially the fact that the ledger board would be attached to the last course of blocks.

I dialled down artistic vision and option 2, with joists sitting on the wall with 'Tony tray' like detail looks now much more sensible to me.

Opinions please?

 

 

Edited February 3, 2021 by Olf

[Gus Potter]

You may be as the cost of maintaining the structural intergity, robustness and tying it all in may far exceed the cost of just adding in a bit of insulation else where. Ledgers can be fine but best to have some compression in the masonry as you need the weight above to top the masonry from rotating etc.. Hangers are not so good at taking horizontal loads, especially if they are retrofitted. When you take away a wall you need to remember that even if it does not appear to be holding something up it may be providing lateral stability to another wall that is, and that wall may be subject to horizontal wind load. That is your starting point.