Roofs and flat roofs
What should you ask if the loft has no underlay beneath the tiles?
Ask whether the surveyor could see the underside, and whether water staining or daylight was there. An older roof can be tile or slate on battens with no underlay. That is not automatically a fail, but it means driving rain and snow can blow in, and a slipped tile leaks straight through.
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?
Underlay, sometimes called sarking felt, is a second line under the covering. Many roofs built or re-covered in recent decades have it. Many older ones do not. A home survey that enters the loft can see the difference. If the loft is marked not inspected, the report has not confirmed either the underlay or the timbers.
Adding underlay means stripping the covering. That is a large job, and the price is a roofer’s quote for this roof, not a figure we can invent. Sometimes the practical step is to keep the covering maintained and to accept the limitation. Ask the surveyor how they rated it and what they could see. Do not upgrade the job in your head.
What should you ask your surveyor?
- Did you enter the loft, and was underlay absent or only not visible?
- Was there daylight, staining or damp insulation?
- Is the rating about the missing underlay, or about slipped coverings as well?
What are the typical next steps?
- If the loft was not inspected, arrange access if the seller will allow it. A torch from the hatch is not the same as moving boards.
- Ask a roofer whether this covering can be maintained from outside, or whether stripping is the only way to add underlay.
- Budget from written quotes. The absence of felt is not a number.
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 roofing felt the same as a vapour barrier at the ceiling?
No. Underlay sits under the tiles. A vapour control layer, if any, is at the ceiling. They do different jobs.
Does no underlay mean the roof is illegal?
No. Older roofs remain lawful. Building regulations for new work are a different question, and a home survey is not a building-control approval.