Cooker extractor vent for GRP flat roof

[pilsbury]

Having a right job finding the right thing. Building a flat roof on the extension. The cooker extractor fan will be mid wall some distance from external walls. Looking to vent straight up through the roof. I've seen several possible solutions, but unsure if they are right for my purpose. Plus loads say for felt roof/bitumen roof/epdm roof - none seems to specify GRP. Needs to be fairly long - 460mm below the flange to go below the 200mm joists and warm roof decks and insulation, then the cowl bit on top.

This is the sort of thing I was thinking of - any suggestions for my specific use?

https://www.roofingsuperstore.co.uk/product/oft-1f110-flat-roof-ventterminal.html

 

[Nige F]

I'm thinking that with GRP you need to form the upstand in with the roof. If you use one like the pic. you won't seal the glassfibre to the flat base of the vent. Just a suggestion - use 110mm soil pipe wrapped with some plastic bags, apply the resin and mat to this and the roof in one, then slide the pipe out - giving you a GRP tube that will fit a 110 soil pipe. Use a mushroom vent on top and a (glued on ) flashing sleeve to keep the water out.

 

[pilsbury]

Like the idea. Why not just leave the soil pipe in place and fit a flashing sleeve to cover the pipe/GRP join?

 

[rssteve]

Glass fibre up the soil pipe. Then cut the pipe and grp off. Then put a mushroom cowl on the top. The mushroom cowl will also stop any water getting in between the grp and pipe.