Spray foam on roof

grumbler

Elevenpm11 said:

grumbler said:

I am no expert, but if there's felt under the battens, I don't see any point in removing the foam. My understanding is that typically foam was spayed (wrongly) directly to the tiles and battens instead of (to compensate for the lack of) felt or membrane.

If the rafters are fully covered, I'd clean their bottom surface to let them breath.

  An issue though is whether the foam just being on the felt might impact the longevity of the felt and any battens.

The battens are above the felt and cannot be affected in any way.

The felt either was affected (by the solvent when spraying) or wasn't. Removing the foam now will have no effect.

Jeepers_Creepers

When you removed that test bit, 11pm11, it was during this cold wet spell? And the exposed rafters appeared dry?

I think, as with others, I'd probably go for the 'negotiate a bit off' route, and then perhaps just live with it until you have to do something about it - either when the roof has come to the end of its natural life and needs recovering (you say some tiles are already slipping?), or else if you think you'll need to have it sorted for resale. Or, just tackle it slowly as you want.

Does it come away cleanly from the felt? A sharp blade run firmly down against the rafters should separate it easily enough from that part, but you'd need to stop before the tip cuts through the felt! There must be a tool that you can cobble together to do this - a bit like a hand-sickle but with a guide added to the blade to run along the bottom edge of the rafters and control its cutting depth.

The only reason I can think of why it was done in this case (since the felt is still present) was to hopefully make the loft space better for storage. But this doesn't really work unless you also add heating to that space - or it'll still be colder than the house itself, and still receive moisture from the house, so it'll still be damp. The only way to keep away damp is proper ventilation. And once you add ventilation, the room will be back to 'outdoor' temps. So, seemingly a bit nuts?

Elevenpm11

Jeepers_Creepers said:

When you removed that test bit, 11pm11, it was during this cold wet spell? And the exposed rafters appeared dry?

I think, as with others, I'd probably go for the 'negotiate a bit off' route, and then perhaps just live with it until you have to do something about it - either when the roof has come to the end of its natural life and needs recovering (you say some tiles are already slipping?), or else if you think you'll need to have it sorted for resale. Or, just tackle it slowly as you want.

Does it come away cleanly from the felt? A sharp blade run firmly down against the rafters should separate it easily enough from that part, but you'd need to stop before the tip cuts through the felt! There must be a tool that you can cobble together to do this - a bit like a hand-sickle but with a guide added to the blade to run along the bottom edge of the rafters and control its cutting depth.

The only reason I can think of why it was done in this case (since the felt is still present) was to hopefully make the loft space better for storage. But this doesn't really work unless you also add heating to that space - or it'll still be colder than the house itself, and still receive moisture from the house, so it'll still be damp. The only way to keep away damp is proper ventilation. And once you add ventilation, the room will be back to 'outdoor' temps. So, seemingly a bit nuts?

Thanks! Yes it was last weekend when it was quite cold. It all seemed quite dry up there although I only inspected part of it closely.

When I pulled it off it did leave residue on the felt. I didn't try too hard to scrape it off but I think it I would be able to remove a fair amount of it with a scraper like you suggest.

I think you are spot on regarding storage. At the same time as applying the spray foam they also added a load of platforms for storage in the attic. Probably the best thing to do is after we have moved in I put a humidity sensor up there to work out what's going on and if necessary remove the spray foam and/or add some ventilation.

Elevenpm11

Here is a photo

Elevenpm11

I had thought that most of the replies would be something along the lines of "It's another spray foam disaster, you'll need to replace the whole roof at some vast expense". Thankfully it seems that this isn't the case!

Even if we have to have the roof redone - perhaps even to just replace the felt - then the good thing is that as the felt has not been removed we should be able to reuse all of the tiles. That alone will save us a fortune!

Davesnave

If you can get it away cleanly as in the picture, it's not a problem beyond the physical labour involved. The rafter we can see looks in good condition. To my mind it's still worth renegotiating on the basis of having to remove it and, presumably, to insulate conventionally, if there's no material between the joists.

grumbler

I can only repeat - there is no point in removing the foam. In this case this foam is no different from, say, 'easy-fit' polystyrene boards for filling gaps between rafters

I am sure, any knowledgeable surveyor will say the same.

FreeBear

Elevenpm11 said: Here is a photo

Doesn't look too bad. The foam hasn't encapsulated the timbers, and the felt has stopped it from sticking to the tiles & battens. As long as ventilation is adequate, the foam could be left in place.

fimacdoodle

Found this old thread - surveyors now recommend to mortgage companies to give a nil property value offering, rightly or wrongly - this happened to me recently when I was selling a rental property. I had to remove it all at great cost. Beware !