Selling a house with spray foam
Planning to sell: area matched the paperwork, foam depth up to twice the stated 100 mm
near Coventry · Recent inspection · Spray Foam Inspection
The house
Detached two-storey house, concrete interlocking tiles, a single-storey side wing with its own loft, closed soffits without vents, and the boiler in the loft.
The foam
Open-cell, sprayed in 2021 onto felt, quoted under the Green Homes Grant. It buries most rafters, misses others and left two short stretches bare; near the ridge, unstuck from the rafter sides, it leaves gaps to the felt. It also covers lights, cables and the boiler wall.
The paperwork
Quotation, product warranty, TrustMark lodgement and an insurance-backed cover notice. Not provided: signed contract, pre-installation roof survey, product approval, condensation risk assessment. The quotation refers to 10 years of insurance-backed cover; the notice states 2.
Why they called
Planning to sell one day, the owners wanted to know what is in the roof and whether it is doing harm.
What was measured
- Paperwork 152 m² at 100 mm; measured 152–157 m², with the foam about 150–200 mm deep where measured.
- 12 timber readings, all below 20%; the two highest, 18.6% and 19.6%, at the ridge.
- Main loft air 2.4 g/kg wetter than outside, and as moist as the room below or slightly more.
- Eaves filled with foam in every section seen bar one open eaves box, against about 0.125 m² of opening per side on the stricter case.
What it means
The two highest readings sat at the ridge, where warm, damp air rises and the foam leaves the felt open to it. With the eaves sealed and the loft as moist as the room below, the inspector's opinion is that household moisture is staying in the roof.
What happened next
A roofer first, before anyone touches the foam, since water marks near the ridge and elsewhere could not be traced from inside. Then an electrician for the lights and cables, and a gas engineer for the boiler and its flue. Then, soon, the missing documents, and the ridge re-checked after a winter.
For other homeowners
Check depth, not just area: here the area matched the paperwork, but the foam was up to twice the stated thickness in places and missed rafters in others.
Read the guide: Selling a house with spray foam: step by step · Selling a house with spray foam: what to tell buyers (including the TA6)
The honest limit
One sunny afternoon, loft warmer than the room below; not a winter night. The felt and timber behind the foam were out of reach, the roof was seen from the ground, services were not tested, and from inside, condensation and rain at the ridge could not be told apart.