I have an existing bitumen flat roof maybe 30 years old but still serviceable. I suspect it must be a cold roof but has had no insulation on the underside. I have taken down the ceilings and there is no evidence of past condensation although it is impossible to adequately ventilat, as the joists run to a blank wall. I was intending to put in 100mm celotex, can this increase the possibility of condensation and sweating problems, logically to me it seems to make it less likely.
Thank you Jord I was intending to put in a vapour barrier you think that will do the trick? There are so many opinions out there it's difficult to get an idea of the risks.
Yes I can fit soffit vents on one end but then it hits a blank wall the other end which is a party wall
Yeah. Cut the deck back, sit vertical batons on top of joists and fix to wall. Plywood up the batons then cap off with a length of tilt fillet.
Thanks for that Dan, but I think I have decided as the roof is not in the full flush of youth to invest in a warm roof and not insulate the underside.
If you insulate above the flat roof part and use Kingspan TR27 or Celotex Crown-Up of crown-Fix or something on to that. Use a good Phenolic insulation like Kingspan K110 or Kingspan TP10 maybe. Both of which will give great U-values