Hello,

I am looking at a retrofit project (theoretical study). The project involves the retrofit of a Wimpey no-fines concrete terrace block.

I will be specifying an EWI to the walls, but I was wondering if anybody could kindly offer some suggestions on what would be the optimal solution in terms of thermal bridging/continuity of insulation concerning the single-storey section/flat roof (as attached indicative photo).

Posted By: djhJust put EWI on the single-storey section as well?

This.
BTW, you may want to change your username to avoid spam.

Posted By: davidlithy@gmail.comSo, the EWI on the main elevation abutment would extend and sit on an insulated single-ply membrane (with some sort of flashing/trim). On the single-storey walls, the EWI would extend up to the finished roof level and again finished with a trim/flashing.

Sounds about right. We have some aluminium flashing on the roof-wall corners of our flat roof, that were formed to shape by the installers. There's some flashing let into the render on the wall above that roof. In our case we have a parapet around the edge, with an internal downpipe to drain the roof, but you could use gutters and an external downpipe in the usual way.

I'm not sure why the big lump of timber is needed? I'd be inclined to secure the batten on the outside with a shorter screw - either a special one designed for screwing into insulation, or use a plug fixed into the insulation with some resin glue. I'm assuming the insulation is something relatively rigid, like EPS.

The largest load the flashing needs to resist is probably something like a ladder leaned up against it, and a person scrambling on and off it.