Roofs and flat roofs
What did the visit record about diminishing courses of stone slate, about the farmhouse ridge, and about nail sickness the loft lamp did not prove?
The visit recorded diminishing courses of stone slate on the slopes in view, and the farmhouse ridge as the line those courses run toward. It recorded nail sickness only as a concern the loft lamp did not prove. The survey has not decided that the fixings have failed, because the lamp did not show the nails. It has not decided that the ridge mortar is sound. Diminishing courses describe the laying pattern. They are not a test of every peg or nail under the stone.
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?
Stone slates are often larger at the eaves and smaller toward the ridge, which is what diminishing courses means. Nail sickness is the failure of nails or pegs so that slates slip. A loft lamp shows only the underside the hatch can reach, not a catalogue of fixings. The surveyor should not turn a dark loft into proof. Slipped slates outside are a separate observation from an unproved phrase about nails.
Ask the solicitor whether slates have slipped and whether a stone-roof firm has reported on the fixings. The home survey's lamp was not that report. A specialist can judge nail sickness where slates can be seen from a safe platform. Do not tell a lender the farmhouse ridge was passed because the courses look traditional. The pattern was recorded. The sickness was not proved.
What should you ask your surveyor?
- Which slopes showed diminishing courses, and from where?
- What did the loft lamp actually reach under the ridge?
- Does the report say nail sickness was not proved?
What are the typical next steps?
- Read diminishing courses as a laying pattern.
- Keep nail sickness as unproved by the loft lamp.
- Ask a stone-roof firm if slipped slates need explaining.
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
Do diminishing courses mean the stone is original to the farmhouse?
They mean the courses get smaller toward the ridge, which is traditional. They do not date the stone or prove nothing has been relaid. The survey did not trace quarries or repairs. The farmhouse ridge was the line in view. Age of the covering stays outside this note.
If no slate has slipped, can nail sickness be dismissed?
The loft lamp did not prove nail sickness, so it also did not disprove it across the roof. Absence of a slipped slate on the day is not a fixing test. The report leaves that point unproved. A later slip would need its own look. Do not convert a limited lamp into a clean bill.