DIY Doctor

Leaking Spray Foam Roof and Damp Issues

Postby SprayBodge » Tue Nov 17, 2020 10:53 am

Unfortunately I’m the owner of a spray foam roof. The survey when I bought the house didn’t flag it as an issue but soon after buying I realised it was a ticking time bomb.

The loft is boarded out and has damp patches along the edges. The spray foam doesn’t extend into the eaves, only up to.

Is adding ventilation with soffit vents likely to be beneficial or am I looking at a reroof? Roof is 60’s and tiled with felt so the tiles could presumably be reused where the foam isn’t attached.

Any advice would be very welcome.

Thanks.
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Postby stoneyboy » Thu Nov 19, 2020 10:07 pm

Hi spraybodge
It is very unlikely that venting the roof space will make any difference.
Suggest you investigate areas where damp is occurring but you will probably end up having to redo the roof construction - insulation, felt, battens, tiles.
Regards S
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Postby SprayBodge » Fri Nov 20, 2020 8:55 am

Thank you for the reply. You think even if I added a number of ridge vents and soffit vents that it would still be a big issue?
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Postby stoneyboy » Fri Nov 20, 2020 10:34 pm

Hi spraybodge
Sadly spraying foam on the underside of a tiled roof leaves no gap for ventilation so even if you added vents there would be nowhere for the air to go.
Regards S
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Postby SprayBodge » Sat Nov 21, 2020 9:58 am

stoneyboy wrote:Hi spraybodge
Sadly spraying foam on the underside of a tiled roof leaves no gap for ventilation so even if you added vents there would be nowhere for the air to go.
Regards S

If I installed ridge vents then would you not have cool air coming through the soffit vents and then warmer air venting out of the top of the roof? Basically trying to convert an ‘attempted warm roof’ into more of a cold roof.

Also my foam is sprayed to the felt rather than the back of the tile if that makes a difference?

I’m sure you’re far more knowledgable than I am on this so not questioning you on the validity of what you’ve said, just trying to learn more about why this may not work. Thank you.
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Postby stoneyboy » Sat Nov 21, 2020 9:32 pm

Hi spraybodge
Condensation will form towards the outer side of the foam, it will not be able to escape because the under felt will seal it in. The only way out is to run down towards the edges. By all means try fitting vents and if it doesn’t solve the issue you know what to do next.
Regards S
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Postby SprayBodge » Thu Nov 26, 2020 10:03 am

Thank you for the advice, really appreciate it.
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