Age and type of house
A Victorian slate roof has been covered with a bitumen-like coating. What of the slates can the survey no longer see?
The slate surfaces, the nail fixings and most of the laps. A Victorian roof coated with a bitumen-like layer hides the slates underneath. The surveyor can describe the coating, cracks in it, and ponding if the slopes were visible. They cannot say each slate is sound, and they do not strip the coat. A coated covering is not certified. Decay under the layer stays unseen, including nail sickness that a bare slate roof might have shown.
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?
Bitumen and similar roof paints were spread over old slates to stop leaks without relaying them. The coat can seal the surface and also trap water, hide slipped slates and hide nails that have rusted away. From a ladder or the ground the surveyor sees the coat's crazing, blisters, patches and the edges at the ridge and verges. They do not scrape it off. Where a slate edge still sticks out, that edge is the only slate they can comment on directly. The rest is an inference from the ceiling stains and the loft, if the loft was entered.
Do not tell a roofer the slates have been passed. Tell them the covering is coated and the slates were not seen. A loft that smells damp, or a ceiling that stains, is a separate observation and still does not map every nail. If the coat is rating 3, serious or urgent, get written quotes before you commit. Those quotes should price what the roofer can see and should say what they too cannot see until the coat comes off. The survey has not produced that price and should not be asked to invent one.
What should you ask your surveyor?
- Which slopes are coated, and were any bare slate edges still visible?
- Did you enter the loft under this coating, and what did the sarking or rafters show?
- Are you rating the coating rather than claiming the hidden slates are sound?
What are the typical next steps?
- Tell a roofer the slates are hidden under a coating.
- Do not scrape the coat off during a viewing.
- If the covering is rated serious or urgent, get quotes before you are legally committed.
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
Does a shiny coat mean the slates were renewed?
No. It often means old slates were painted over. Renewal would show new slates, which this coat is hiding.
Can the survey see nail sickness through the coating?
Not reliably. Nail heads and most laps are covered. The report should not claim those fixings were inspected.