Flat roof flashing for stove flue

[geraldthehamster]

Hello

People were kind enough to offer helpful advice in response to my previous stove query. I have another, about the appropriate roof flashing.

Twin wall flue (6” internal) will exit vertically through a flat roof (OSB and EPDM).

I assume that I need the type of flashing at the link below, either fixed with mastic and roofing screws, or with EPDM flashing.

I’m not certain which size I need. The external diameter of the flue is 8”, and the hole it will go through needs to allow 60mm clearance all round.

Several of the flashings have my size of flue within the range of sizes to which they can be trimmed. So which one do I choose?

Also, I read somewhere that the high temp flashing is required if installed less than 5m above the stove (which this will be). Is that right?

https://www.flue-supplies-uk.co.uk/...a-KC-Twin-Wall-Insulated-Pipe-For-Metal-Roofs


Many thanks


Richard

 

[catlad]

Those look identical to the one my mate fitted in his man cave for his woodburner and he is a plumber.
sorry I can't help on sizes.

 

[rssteve]

I've just been through this. It's abit rubbish really as I have a cold roof but the regs say that when going through a ceiling void a ventilated fire stop must be used. This gives free air from the roof into the void and out my vented eaves. The idea is to stop the dead space from overheating if there is no ventilation. Luckily there is some new fire stops which solve it. There is a bungalow one for if the roof is ventilated like mine. Then there is a dinak dinsulator (sp) for a warm roof.

Onto the roof side I actually fibreglassed an upstand rather than silicone the flashing to the roof. My thinking is there won't be as much water trying to get past the silicone seal if it's on an upstand. Now onto the flashing size the smaller 1 will fit but as the base is so small, it means you won't have enough distance to the wood combustibles on the roof. I think I need the 1 with the base size approx 410mm from memory. To give me 60mm either size of the 200mm twinwall and have enough extra to screw onto the upstand.

 

[geraldthehamster]

Your setup is different from mine. I don't have a ceiling void, just a single storey warm flat roof: Joists-OSB-Celotex-OSB-EPDM.

Anyway I rang my supplier and asked them. Their advice was to use a high-temp flashing, and the largest available in the range, to be sure of covering my hole. Of course this also happens to be the most expensive, but I can't fault their reasoning.