Spray foam and lenders
Why does blocked eaves ventilation matter if foam has been sprayed between the rafters?
Because a pitched roof often relies on air moving from the eaves to keep the timbers and the underlay dry. Foam that fills the eaves gap can stop that air. RICS warns that incorrectly installed insulation can lead to dampness and uncontrolled condensation, and that a leak you cannot see can rot the timber.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
A surveyor looks at whether the eaves are filled, whether vents are blocked, and whether any staining is visible at the edges the foam did not cover. They cannot see the top of the rafter where the foam is stuck to it. The consumer guide advises photographs from before and after the installation for that reason. If those photographs do not exist, say so to the lender and the solicitor rather than pretending the roof was inspected in the usual way.
Opening the ventilation path may mean removing foam, which can damage felt and tiles. That is a roofer’s method, priced after a look, not a figure in the RICS guide. Do not drill vents through a foam-filled slope as a weekend experiment. Ask the lender first whether this installation is acceptable at all.
What should you ask your surveyor?
- Are the eaves vents blocked by foam, or could you not get to the eaves?
- Did you see condensation staining or only the foam itself?
- What could you not inspect because of the foam?
What are the typical next steps?
- Write down, for the lender, exactly which parts of the roof could not be seen.
- Ask a roofer how ventilation would be restored, without instructing removal until the lender has answered.
- Ask the seller for the before-and-after photographs RICS recommends were kept.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
Is a ridge vent enough if the eaves are full?
The survey has not designed the ventilation. A ridge vent does not automatically replace a blocked eaves path. Ask a roofer who can see this slope.
Does felt under the tiles change the answer?
It changes how the roof was meant to breathe. The surveyor should say if they could not see the felt. Do not assume a breathing membrane is under the foam.