Spray foam on roof

Elevenpm11

We are buying a house that had spray foam applied on the inside of the roof between the joists a few years ago. We have budgeted for a new roof as our surveyor raised it as a major issue, explaining that the roof would last another 50 years with some care if the spray foam hadn’t been applied. I understand that it can cause rot in the timbers and battens and make it difficult to repair tiles.
We visited the house recently and I investigated the spray foam and it is very soft - I think it is the “open cell” type. I was able to pull a section of it off easily with my hands and reach the sides of the joists and the felt behind it.
I therefore think that I might be able to remove all of the spray foam by hand. This will take a long time, but if it can save having to replace the tiles on the roof it would be worth it.
Would this work and saved the roof? If so, does anyone have any good tips?! 
Thanks in advance.

grumbler

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.

Jeepers_Creepers

Is such spray foam always bad? Can't it work well in some situations?

FreeBear

Jeepers_Creepers said: Is such spray foam always bad? Can't it work well in some situations?

If the building has been designed with spray foam in mind, then it is a very effective solution - Quite common in the USA, but their houses are not designed to last more than 50 years.

In the UK, on existing buildings, it is generally a bad idea.

stuart45

Roofs in the USA are usually boarded and shingles are a common roof covering. Slates and tiles don't always work so well with hailstones the size of golf balls.

Davesnave

It's much the same as any other problem you find with a house, and most of us find things! If you think removal is just tedious and relatively easy, then this shouldn't stand in your way, provided the house is otherwise what you want at a price you consider fair. The roof tiles must be in fair condition if the surveyor implied they had 50 years left in them.

Being MSE, if it were me, I might use the surveyor's report to negotiate further on the price if I felt there was a possibility of the vendor sharing the cost of removal and the risk of unseen damage, even if I thought this expense might not occur.

Elevenpm11

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.

Yes that's what I was wondering. I am hoping it has been applied to the underside of the felt only all around! The bottom surfaces of the rafters are clear, but their sides are not. An option I might investigate is to just pull the foam away from the sides of the rafters too. An issue though is whether the foam just being on the felt might impact the longevity of the felt and any battens.

TELLIT01

If you do plan to remove the foam yourself make sure you are wearing a good mask and other protective insurance.  There could be a lot of dust generated.

Elevenpm11

In response to FreeBear:
house was built in the 1970s and has clay tiles. They look in good condition, although a few have slipped. I therefore don't think spray foam was appropriate. I assume it was applied only for insulation reasons rather than to save the roof. The issue will be to work out why it was applied - is the house freezing without it or does the attic have a lot of damp without it?!

Elevenpm11

Davesnave said:

It's much the same as any other problem you find with a house, and most of us find things! If you think removal is just tedious and relatively easy, then this shouldn't stand in your way, provided the house is otherwise what you want at a price you consider fair. The roof tiles must be in fair condition if the surveyor implied they had 50 years left in them.

Being MSE, if it were me, I might use the surveyor's report to negotiate further on the price if I felt there was a possibility of the vendor sharing the cost of removal and the risk of unseen damage, even if I thought this expense might not occur.

If it is unlikely that the spray foam will impact the longevity of the roof then I am wondering whether we should remove it anyway to ensure it causes no problems with an onwards sale. I have seen people on forums talking about it affecting mortgage offers, although this does not seem to be a widespread issue. Re further negotiation - we are thinking about it!

Elevenpm11

TELLIT01 said:

If you do plan to remove the foam yourself make sure you are wearing a good mask and other protective insurance.  There could be a lot of dust generated.

Thanks very much - yes I plan on going full PPE for any removal. It will have to be done in the winter to avoid it being a horrendously sweaty job! There is also so much of it I think I might need 2-3 tips to get rid of it...