OK I understand use of spray foam directly in contact with tiles is a very bad idea and the reasons for that. However what is proposed is using open cell breathable spray foam (Lapolla water based, no HFC's) underneath the existing tar paper that is in poor condition. It is proposed that where the tar paper has splits/holes then it will be first relined from the underneath with a breathable menbrane then sprayed so that the foam will not be in contact with any roof tiles which are in generable good condition with no sign of obvious leaks. This should insulate and provide a bit of extra strength to to existing felt noting in passing that breathable open cell foam remains flexible and does not have the rigidity of waterproof closed cell foam. I'm told also that use of the open cell foam will still allow the wooden trusses etc to still breathe. Can anybody who has experience of this comment on the practibility of this idea and potential problems if any. The alternative as I see this is a full scaffolding, removal of tiles and replacing of lining/batterns
Are you a tradesperson and able to answer this question?
I would stroghly advise that a strip, refelt and batten tiles returned, along with new ridge tiles fitted where required fix with new mortar. This may be more expensive but in the long run a more professional job and of course monies added to the value of the property
Yours thankfully
Mr Paul Emeney
Peconstruction.co.uk
A lot depends on the age of the roof, if it is quite old then you just as well bite the bullet and get it re felted with a modern breathable felt. Patching is normally only a short term fix, and many patches will end up costing a lot. I always find it strange how people will spend 10s of thousands on new kitchens/bathrooms etc and the most important part of the property is the roof, yet it's never in the budget for renewal?
Hi
Yes it is a bad idea and it’s a bodge that non roofers do. You could do patch repairs on the roof but you can only repair a puncture so many times before you need a new innertude or tyre. But if not leaking why are you even considering doing anything?
If the felt has degraded you are better off stripping and renewing the felt and battens if the tiles are still in good condition. Obviously it is cheaper than replacing the whole roof as you save on the cost of the new tiles. Any good roofer would tell you the same. The use of spray foam on the under side of a roof is a disaster
I know the cost involved in replacing a roof can seem like a lot, but the piece of mind you’ll get from taking that route is worth it. Your roof protects everything you own, bare that in mind when contemplating the outlay. What’s been proposed with the spray foam will not be recommended by any professional and should be avoided.
