Warm roofing and GRP Fibreglassing Single Storey Flat Roof

datarebal said:

Wrong side of the insulation though.....

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Thats true, but we fit the insulation tightly together, gaps are foamed. Vapour cant get to the top deck as its stopped by the foil.

I suppose some microscopic amount of vapour could get through tiny tiny gaps that might exist between the insulation.

We also use foil backed plasterboard, although downlighters pierce through that.

Im not keen on a vapour barrier sheet under the insulation because there is a risk of trapping water if heavy rain falls before the fibreglass is done.

Our original plan was to create a decked area above the flat roof so that we can have a terrace accessed from our kitchen. However, I have been looking at the feasibility of reinforcing the original joists with sister joists. Has anyone got recommendations on grp kits that can withstand footfall? I know that I now need to go for 600 gsm chopped strand matting but want to know a decent resin brand.

Polyroof supply GRP roofing kits, if you give them your specifications they can work out quantities required.
They also give warranties depending on the size of the roof.
I did an approved contractors course with them some years ago.
When taping the deck before applying the base coat we had to use glass mat tapes and not duck or silver tape.
Another thing is they don't recommend using OSB for decking.