Spray Foam
Spray foam insulation is sprayed onto the underside of the roof and expands to fill the gaps. The Energy Saving Trust warns that spraying foam directly onto the underside of a roof can trap moisture and lead to timber rot, especially on older roofs, that it makes roof repairs harder, and that it is effectively permanent. Some lenders and surveyors have been cautious about homes with spray foam. Get independent advice before choosing it.
What to Know About Spray Foam
- Can fill awkward spaces around pipes and irregular timbers
- Open-cell foam carries lower moisture risk than closed-cell foam, according to the Energy Saving Trust
- Never apply it to a leaking or damp roof — fix the roof first
- Hard to remove later: it may mean replacing the timbers it is sprayed onto
- Read the RICS guidance on spray foam and consider lower-risk alternatives first
Price Guide
From about £37/m² (materials only)
Typical UK price guide, last reviewed September 2026. A guide, not a quote.
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Frequently Asked Questions
Does spray foam insulation affect my mortgage or property sale?
It can. The Energy Saving Trust says some buyers struggled to get mortgages on homes with spray foam while lenders reacted to concerns about damp and repairability, although this should be less of an issue where it has been installed correctly. The Royal Institution of Chartered Surveyors (RICS) publishes guidance for homeowners. For most unused lofts, mineral wool at joist level is the lower-risk option.
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