Roofs and flat roofs
What is the difference between a trussed-rafter roof and an older cut roof, as far as a survey can see?
A trussed-rafter roof is usually a row of thin, repeating frames, common from the 1960s onward. An older cut roof is usually rafters, purlins and sometimes a ridge, built on site. A home survey can tell them apart when the loft is open. It does not strength-test either, and Approved Document A is not a certificate for the one you are buying.
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?
The difference matters when someone wants a loft room. Cutting a truss is not the same job as moving a purlin in an older roof, and neither is automatically approved because the room looks finished. RICS home surveys look at what is visible: damp staining, spread, cut members, stored goods that block the view. They do not redesign the loft.
Tell the survey firm which roof you think it is only if you know. Let them say what they saw. There is no RICS price that changes because the trusses are thin. Do not board across a trussed loft and then claim the survey should have seen the feet. Access is a limitation if the view was blocked.
What should you ask your surveyor?
- Which type of roof did you see?
- Were members cut, or only thin?
- How much of the loft was blocked by stored goods?
What are the typical next steps?
- Do not cut a truss to make storage.
- If you want a room in the roof, ask about papers and about the roof type before you buy the furniture.
- Keep a sagging covering separate from a cut member.
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
Are thin timbers a defect?
Not by themselves. Trusses are meant to be thin and to work together. A cut or a sag is the comment.
Does a 1930s house have trussed rafters?
Usually it has a cut roof. The survey should say what this house has, not what the decade usually had.