DIY Doctor UK DIY Forums

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.

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

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?

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

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.

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

Thank you for the advice, really appreciate it.

Homes with open-cell shower froth don't need to supplant the froth when it gets wet, or even after it has been lowered. This may come as amazement on the grounds that there is a typical confusion that all open-cell shower froths assimilate water like a wipe and hold it, yet that is not the situation