Selling a house with spray foam
Selling with a previous owner's foam: all 15 timber readings above 20%
Stockport · Recent inspection · Spray Foam Inspection
The house
Two-storey mid-terrace, plain-tiled pitched roof with a party wall at each end. The middle of the loft has since been boarded, with eaves voids behind plasterboard.
The foam
Closed-cell, sprayed directly onto the tiles and battens with no underlay, on both slopes and the party wall at the chimney end; roughly 50–65mm deep and crumbling in places. Fitted by a previous owner (rafter insulation first appears in the property's EPC records in 2015); later strut removal left openings in it.
The paperwork
None for the installation, the later boarding or the strut removal; only two public EPCs and one page of a purchase survey.
Why they called
Selling, with the buyer planning their own survey. The owner wanted an independent, dated record of the roof void first.
What was measured
- 15 timber readings, all above 20%; ten sat between 20.3% and 21.5% across the loft.
- Highest 56.6%, beyond the meter's accurate range, on a rafter inside an opening left by a removed strut; all three rafters read in these openings were the wettest timber nearby.
- Bare party wall at the chimney end: 19.1 °C against a dew point of 17.1 °C, a 2.0-degree margin, with white salt bloom.
- Loft air 1.6 g/kg wetter than outside, rising during the visit; the room below 0.4 g/kg above outside, read as normal.
What it means
Foam on the slopes, sealed eaves and ridge, no vapour barrier and a bare brick wall: a cold roof with its ventilation taken away. That wall is the coldest surface, and a 2.0-degree margin on a mild afternoon is likely to vanish on a cold night; its salt bloom is consistent with repeated condensation. At the stack and the strut openings, a leak could not be ruled out.
What happened next
First, a roofer at the chimney stack, which has a shrub rooted in its joints, and at the bare tiles in the strut openings, before any foam decision: removing foam first would destroy the evidence of a leak. No roof work was needed before the buyer's survey.
For other homeowners
If your loft was altered after spraying, ask who did it and under what approval, and check those spots first: here, they held the wettest timber.
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 mild early-autumn afternoon, not a midwinter night. Timber under bonded foam could not be read, the boarded floor was not lifted, and the stack was seen from the ground only.