Roofs and flat roofs
Sarking felt sags into the eaves gap and holds a trough. What ventilation and what drainage of that felt were not corrected on the day?
Neither the ventilation past that eaves gap nor the drainage of the sagging sarking felt was corrected on the day. The felt has dropped into the gap and holds a trough, so moisture on the underside of the covering can sit there instead of running outside. The survey recorded the sag and the trough. It has not trimmed the felt, opened the eaves, or shown how air now moves at that point. A trough seen in the loft is a condition note, not a repair carried out during the visit.
Last reviewed 24 October 2026. Written for buyers in England and Wales unless this answer says otherwise. No named surveyor has signed this page. It is general guidance, not a report on your house, and not legal advice.
What is the fuller explanation?
Sarking felt is the underlay beneath the tiles or slates. Where it sags into the eaves it stops acting as a chute into the gutter and becomes a pocket. Water that passes the covering, or condensation on the felt, can collect there and sit against the timber. The same sag can block air that should leave at the eaves. The survey can describe that shape. It cannot say how long the trough has held water, or whether the rafter feet are already soft.
Ask a roofer to quote for easing the felt so it drains outward, and for restoring ventilation at the eaves, as roofing work rather than as something the survey already finished. Tell the solicitor the report records a trough that was seen, not a repair. Do not describe the visit as having cleared the eaves. If tiles must be lifted to free the felt, that opening is a new instruction. The home survey did not lift the covering.
What should you ask your surveyor?
- Where along the eaves does the felt sag into a trough, and where does it still run outward?
- Did you see staining or soft timber at the rafter feet next to that sag?
- Was the eaves air path blocked by the felt, or could you still see a gap?
What are the typical next steps?
- Treat the trough as uncorrected until a roofer eases the felt.
- Ask a roofer to restore outward drainage and eaves ventilation.
- Keep the survey as a record of the sag, not as a finished repair.
Costs vary with the building and with who you instruct. Where this page does not cite a published figure, ask the surveyor, a relevant specialist, or your solicitor for a written quote. Do not treat a forum average as the price.
Also asked about this
If the tiles look even from the garden, is the trough closed?
No. An even roof slope does not show how the felt sits in the eaves gap. The survey saw a sag that holds a trough, which is an underside detail. Garden appearance does not drain that pocket and does not prove air can pass. The covering can look tidy while the felt still dips.
Can the loft visit separate rain under the tiles from condensation in the trough?
Not reliably. Both can wet the same pocket, and the survey did not test the source. It recorded felt sagging into the gap and holding a trough. It did not trace a leak path and it did not measure moisture in the felt. The cause of any water in that pocket remains open.