Spray Foam: What is it?
Spray foam can trap moisture and block inspection of your roof timbers. UK guidance warns that incorrect installation may reduce a surveyor’s valuation and, in some cases, make a home temporarily unmortgageable. If that happens, sellers often face 15–25% cash-buyer discounts until foam is professionally removed and the roof is proven sound. Our specialists safely remove foam, reopen ventilation, and document your roof so you can protect your property value and mortgageability.
Chemical structure of spray foam
Spray polyurethane foam (SPF) is created on site by combining “Side A” (MDI isocyanate) with “Side B” (polyols, catalysts and a blowing agent) to form open-cell or closed-cell foam that cures in place. Airborne isocyanates during application are a key hazard — strict RPE/PPE and controls are required.
Closed-cell
Dense and more vapour-resistant; at rafter level it can block ventilation and trap moisture if detailing is wrong.
Open-cell
More vapour-permeable, but poor design/installation can still imbalance moisture in a cold roof.
Roof physics
Moving insulation to the rafter line turns a “cold roof” into a “warm roof” — condensation control becomes critical.
2) Why removal is often required
Hidden defects & inspection barrier
Foam can conceal leaks, nail corrosion and timber condition, making a full rafter inspection impossible. That lack of visibility drives surveyor and lender caution.
Damp/condensation risk
Poor design or execution can trap moisture behind foam. Over time this can cause decay in rafters, sarking and fixings — especially where ventilation pathways were blocked.
Fire & safety during works
Polyurethane foams are combustible; removal and rework require correct controls. Isocyanate exposure demands professional RPE/PPE protocols.
3) Why lenders care (and how that impacts value)
When foam obscures the roof structure, surveyors may down-value or request specialist reports. Some lenders apply strict policies until foam is removed and the roof is documented as sound.
Surveyor visibility
Limited access to rafters reduces confidence in structural condition and can affect valuation.
Policy triggers
Missing paperwork (product certs, condensation risk calcs, install records) often triggers extra scrutiny.
Sales friction
Buyers face mortgage hurdles; many sales pause until foam is removed and the roof passes inspection.
4) Quantifying the value impact
Where foam renders a home unmortgageable, the buyer pool can shrink to cash buyers. In practice, cash offers often land ~15–25% below open-market value until foam is professionally removed and mortgageability restored.
5) What homeowners should look for
Condensation smells
Musty odours in lofts/upper rooms, especially in colder months.
Visible damp/staining
Dark staining on sarking, damp patches, resin bleed, corroded fixings.
Blocked ventilation
Eaves and ridge vents covered by foam; no baffles; inadequate airflow.
Bowed/soft timbers
Localised softness, delamination, fungal growth, or unusual deflection.
Leak history
Historic leaks now hidden behind foam; no way to inspect nail lines/underfelt.
Missing paperwork
No product certs, U-value or condensation risk calcs, or installer evidence.
6) Paperwork lenders often ask for
- Product certification (e.g., BBA/KIWA) and installer credentials.
- Condensation risk assessment & U-value calculations for the roof build-up.
- Before/after photos, clear access for inspection, and any specialist report.
- Warranty/guarantee and evidence of correct detailing and ventilation.
The science behind spray foam and roof performance
Chemistry & health
SPF uses MDI isocyanate + polyol blend. Isocyanates are respiratory sensitisers — leading cause of occupational asthma — so application and removal require strict RPE/PPE and controls.
Formaldehyde (UFFI)
UFFI is an older foam type. Pure formaldehyde vapour is hazardous; UFFI itself is a solid, but legacy installs may warrant investigation if concerns arise.
Cold vs warm roofs
Insulating at rafter level alters moisture dynamics. Without proper design/ventilation, uncontrolled condensation can damage timbers.
Before & After: Transparency, not guesswork
We record progress videos every two hours as standard, so you can see exactly what’s been done — even if you can’t access the loft.
FAQs
Is spray foam always a problem?
No — certain build-ups can tolerate it. Issues arise when design/detailing is wrong or inspection is blocked. Our survey determines real-world risk for your property.
Will removal damage my roof?
We work methodically with the right tooling, RPE/PPE and disposal process to minimise disturbance, then photograph and log the roof’s condition for transparency.
What do you recommend after removal?
A breathable, high-performance insulation (e.g., multi-foil) with correct ventilation and detailing. It keeps heat in, lets moisture escape, and supports healthy timbers.
Ready to make your loft mortgage-friendly again?
Book a free assessment. We’ll expose and check rafters, take moisture readings, restore ventilation, and provide a clear report for surveyors and lenders.