2 warm flat roofs short pitched roof between

10 Mar 2022
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United Kingdom
So slightly strange set up - my house has a rather complicated roof structure, mostly pitched going up to warm flat roofs. There are 2 flat roofs (about 30 sq m each) warm, torched on felt - and between them is a short pitched roof (about 1.5 m by 6 m) fake slate tiles.
The flat roofs are no issue - but the pitched section on opening up inside there is condensation underneath. Breathable membrane but condensation still an issue ...
There are 2 potential solutions (I think!) - for the pitched section add ventilation above the breathable membrane at the bottom of the pitched roof (glidevale fv250 fascia vent) and at the top with av50 abutment vent. Inside ensure there is a 50mm gap between the insulation and the breather membrane, and then below that ensure a proper VCL so no warm air can get through.
The other solution is to strip the pitched roof and effectively extend the flat roof - so you have flat warm roof, pitched warm section (from the outside in - torched on felt, OSB boards, insulation, VCL) so you are just extending the warm flat roof design up the pitched section.
I've added a very basic sketch to just show the current layout without any details.
Any thoughts from anyone? The second solution makes sense, but I've never seen it anywhere (although the roof design is a little strange!)


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The whole lot needs to be warm really because of contamination from the flatties. In other words you need to have the insulation detail above the pitched rafters. Either that or be able to isolate the airflow betwixt roofs.

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