Roof Survey Foam Spray.

Roof Survey Spray Foam:

The Risks of Insulating with Spray Foam

Spray foam between joists needs venteration.

Recently, I was asked to perform a roof survey on a property in Camden where spray foam had been applied to the underside of a pitched roof. The property was on the market, and a survey report from a Royal Institution of Chartered Surveyors (RICS) surveyor advised the customer that the spray foam between the rafters should be removed, as it was blocking the roof’s ventilation and potentially compromising the roof's stability. My task was to inspect the roof to verify whether the insulation should indeed be removed.

My Findings

Upon inspecting the roof, it was clear that spray foam had been applied between all the rafters, effectively preventing airflow into the loft space. I also noted that the foam was sprayed directly onto the back of the roof tiles, creating a complete seal that blocked any movement of air.

Conclusion

The presence of spray foam insulation directly on the underside of the roof tiles prevented essential ventilation. This lack of ventilation could potentially cause the battens supporting the tiles, as well as the fixings attaching the tiles to the rafters, to deteriorate and rot prematurely if left unaddressed. Over time, this could also lead to the decay of structural timbers.

Spray foam that has been removed from between joists

Findings After Spray Foam Removal

Two weeks later, I conducted a follow-up roof survey after the spray foam had been fully removed from between the rafters. This inspection revealed that the foam had been tightly installed against the tiles without any ventilation gap. There was visible deterioration on the battens and some structural timbers.

Additionally, I observed that the removal process had damaged the back of some tiles. Given the roof’s age, it’s possible that some of this damage predated the spray foam installation. Regardless, it was evident that the roof needed to be replaced and that proper insulation should be installed at ceiling level, leaving the loft space as a "cold space" to allow ventilation.

The Takeaway on Spray Foam Roof Insulation

In general, spray foam insulation on pitched roofs is problematic and is often condemned by surveyors due to the risk it poses to ventilation and roof structure. For most properties, spray foam in roof spaces is best avoided to maintain a healthy roof environment and to avoid long-term structural issues.