Spray foam insulation is sprayed onto the underside of a roof, usually between and over the rafters. It has been sold to many homeowners as a quick way to insulate a loft or hold a tired roof together. In recent years, many homeowners have found it causing problems when they come to sell or remortgage.
This guide explains why spray foam worries lenders and surveyors, what it can hide and what a roof survey can and can’t see.
Why it causes concern
The main worries are:
- It hides the roof. Rafters, battens, underlay and the underside of the slates or tiles are covered, so their condition can’t be seen.
- It can trap moisture. If the foam stops the roof timbers from drying out, they may stay damp, which can lead to decay.
- It’s hard to remove. Once bonded to timbers and coverings, taking it off is a big job.
- It can be used to hold failing roofs. Sometimes it’s sold as a way to stop slipped slates, which may cover up a roof that really needs proper repair.
Because of this, some mortgage lenders ask for extra reports or won’t lend on homes with certain types of spray foam.
Open-cell and closed-cell foam
There are two broad types. Closed-cell foam is dense and rigid. It’s the type more often linked with trapping moisture and bonding slates or tiles in place. Open-cell foam is softer and lets some moisture pass through. It can still hide the timbers, and lenders may still ask questions about it. The type, how it was installed and whether the roof was ventilated all matter. Removal, where it’s needed, is a specialist job, and the roof should be checked once the foam is off.
Want a roof surveyed? We cover London and the South East, with written reports and photos from £150 including VAT. Book a survey or call 07833 053749.
What a roof survey can see
From outside, a survey looks at the coverings, ridges, hips, valleys, flashings, chimneys and gutters as normal. Slipped slates or tiles, damp staining and other defects can still be seen from the ground, from windows and, where applicable, by drone.
From inside, a survey can note where foam has been applied, how much of the roof it covers, whether it looks wet or has come away, and whether any timbers or underlay are visible at the edges or around gaps. Thermal imaging and moisture readings can sometimes add to the picture.
What it can’t see
A survey can’t see through foam. It can’t confirm the condition of rafters, battens or underlay behind it without the foam being removed. We don’t cut into foam or open up the roof. If the condition of the timbers needs confirming, the report says so. A survey also can’t tell you whether a particular lender will accept the property. You’ll need to check that with the lender.
If you’re buying a house with spray foam
- Ask the seller when it was installed, by whom, and what type of foam was used.
- Ask for any paperwork from the installer.
- Tell your mortgage lender or broker early.
- Consider a pre-purchase roof survey to record what can be seen inside and out.
Our guide to roof surveys vs RICS surveys explains how a roof survey fits with your main survey.
Quick answers
Will spray foam stop my slates slipping?
It may hold them in place for a while, but it covers up the cause and hides the roof from inspection. Getting the roof surveyed first is wiser.
Can you tell if my rafters are rotten under the foam?
Not without the foam being removed. We can report what’s visible and any signs of damp, and say if further investigation is needed.
Will my lender accept spray foam?
It varies by lender and by the type of foam. Check with your lender or broker directly.
Related services
More advice
- Condensation or a Roof Leak? How to Tell
- Do I Need a Roof Survey When Buying a House?
- Slipped Slates and Nail Fatigue Explained
- Roof Checks Before a Loft Conversion
- All advice
This guide is general information about roofs and roof surveys. It isn’t legal, insurance or structural engineering advice; for those, speak to a suitably qualified professional.