Roofs and flat roofs
Lumps of mortar torching have fallen onto the loft insulation. What does that debris tell you about the underside of the tiles, and what leak has it not proved?
The debris tells you that mortar torching has come off the underside of the tiles and dropped onto the insulation. Torching is the mortar that older roofs used under the tiles, and lumps on the loft floor mean that bedding has detached. Tiles can then be less held from below, and driving rain can pass the laps more easily than when the torching was intact. That has not proved a leak. Fallen mortar is not a dated stain, and the survey has not shown water coming through the covering on the day.
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?
Torching was a way of closing the underside of a tile or slate roof from inside the loft. When it falls, you learn that this seal is incomplete where the lumps came from, and that the insulation now has mortar sitting on it. You do not learn that rain entered last week, or that every tile on the slope is loose. The survey can describe the debris and the bare undersides it could see. It cannot turn those lumps into a leak history.
A roofer can say whether the remaining tiles are still securely fixed and whether the fallen torching needs any local making-good, or whether the roof is better left without new mortar. Do not ask for the insulation note to be rewritten as an active leak unless water was actually seen. Tell the solicitor the defect recorded is detached torching, not a proved failure of the covering. The survey has not specified a full strip of the slope.
What should you ask your surveyor?
- Where on the slope had the torching fallen, and where was it still in place?
- Did you see daylight or water at those tiles, or only the fallen mortar?
- Was the insulation merely covered in debris, or was it wet as well?
What are the typical next steps?
- Read the lumps as detached torching, not as proof of a leak.
- Ask a roofer to check the tile fixings where the mortar has fallen.
- Keep any ceiling stain as a separate note until water is actually traced.
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
Should new torching be put back under the tiles?
Not on this note alone. Fallen torching shows the old mortar has detached. It does not specify a new mortar coat, and some roofs are left without it once the tiles are properly fixed. That choice is for a roofer, not a conclusion the survey has already made.
If the insulation is compressed by the lumps, is the loft wet?
Weight on the insulation is not wetness. Mortar can lie dry on the quilt. The survey has not called the loft wet merely because torching fell onto it. Asking about it again later still leaves this torching point outside what the survey decided.