wood burner flue through flat roof

[nick60]

afternoon all, hope some of you folks can advise me on this (sorry it's a bit long).

I have a flat roof currently being constructed - the bottom layer of felt has been torched on to give me some basic waterproofing and the roofers are due back soon to finish the job. I'm installing a wood burner as part of this project and the flue has to go through the new flat roof. The flue is not yet in position, nor is it likely to be when the roofers return - not a great situation I know, but I want to plan for the flue as best I can. The flue will necessarily be quite close to the edge of the flat roof where it abuts the main house wall. There are complications;

1. the near edge of the flue will only be 80mm from the wall/edge of flat roof. Also, there is some upstand ventilation detail down the edge of the flat roof which makes everything very tight space-wise. The roofers were talking about handling this part of the roof 'in liquid' (whatever that means?) but I don't think that will work because of point 2 below.

2. the BCO is hot on the topic of clearance between flue and combustibles. It's a twin wall flue and I understand I need to clear all timber within 50mm of the flue.

The best idea I've come up with so far is to identify the rectangular area that gives me the 50mm flue clearance. It's a 200mm flue so this will be approx 300mm square. I'd then divert the upstand ventilation around three sides of this square and cut the timber deck away within it. To make things watertight I would use a flat roof lead flashing for a 200mm pipe. The ones I've seen have large bases which could be worked into the masonry on one side, and over the upstands on the other three sides. The lead would need some support but I could do this with metal straps or some other non-combustible material. Could be tricky to get this right and I might end up needing a bit of bespoke lead work, but it's the only way I can think of satisfying the BCO and being watertight. What do you think? Any better ideas greatly appreciated, TIA
Nick

 

[big-all]

you need to conctact your supplier or the manufacturer
there are special conditions when installing near inflamable materials
clearence needs to be in feet not inches from flamable materials
you can use fireproof boards and an air gap but your burner will possibly need to be greater than 3" away if you double line the flue you will probably be ok closer than 6" but you need to check

 

[nick60]

thanks big-all but I'm up to speed on the clearance requirements. It's a twin-wall flue, 6" inner and 1" insulation to give a 200mm finished flue diameter. The manufacturer specifies the clearance requirement as 50mm which is fairly standard for twin-wall I think. The bigger clearances you mention are presumably for single skin flue / stovepipe. The bit I really need help with are the roofing / lead work aspects

 

[big-all]

i have an R1 from hot spot on a 30 degree slope with a boot designed for less than 2m from the stove
http://www.thehotspot.co.uk/Products/Relax_workshop_Heaters/Relax_Stoves.asp

i will see if i can find a picture
simmilar to this
http://docs.google.com/viewer?a=v&q...x07_SX&sig=AHIEtbSWp8yE_JsVhcwrnUXBznB__ioSDg

 

[nick60]

I'm looking at this now, thanks

 

[Nige F]

Relax- don`t do it Rubber boots Most roofers can @ least leadburn a slate - they pinched most of that work from us plumbers . There was a guy used to post here - leadworker - even had vids of his work

 

[nick60]

done it! have now got some neat upstands around the flue area. Means I can cut away the deck within this area as much as I need to. Main benefit is that I can tell the roofers to finish off and I can get the flue fitted later. Will finish off in lead somehow and BCO will be happy - no timber anywhere near the flue!