Roofs and flat roofs
What is torching under old slates, and why do surveyors mention it in the loft?
Torching is mortar applied to the underside of slates or tiles from the loft, used on some older roofs to cut out draughts before underlay was common. When it falls off, you may see debris and daylight. Fallen torching is a clue that the covering is moving. It is not, by itself, a quote to strip the slope.
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?
A visual survey from the loft boards, where it is safe to stand, can see gaps, nail sickness and fallen mortar that nobody can see from the street. It still cannot name every slipped nib. Underlay may be absent because the roof never had any, which is a different sentence from underlay that has rotted. The report should keep those apart.
RICS home surveys do not require the surveyor to rake out remaining torching. Do not do that yourself before exchange. If rain is marking the ceilings under those slopes, say so when you ask a roofer whether the slates can be repaired from outside or whether the battens have gone. There is no single national cost for that choice.
What should you ask your surveyor?
- Did you see fallen torching, missing underlay, or both?
- Which slopes still have mortar on the underside, and which are bare?
- Was there staining on the ceilings under those slopes?
What are the typical next steps?
- Leave the remaining torching in place until a roofer has seen it.
- Do not stuff insulation into gaps as a repair. Insulation is not a covering.
- If the loft was not entered, the absence of a torching comment is not a pass. Read the limitations.
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
Is torching the same as pointing on the ridge?
No. Torching is on the underside of the slope. Ridge pointing is on the top of the roof, outside. They fail separately.
Does daylight in the loft mean it is raining in?
A little daylight along a lap is common on an old roof without underlay. Staining and drips are the stronger clue. Ask which one the surveyor saw.