Roofs and flat roofs
What should you ask if a barn conversion still relies on the original timber trusses?
Ask which trusses were seen, and whether any have been cut, plated or left carrying a new floor. A barn conversion is not a new trussed-rafter roof. The old timbers can be the structure. A home survey can look at the members it can reach. It does not prove the conversion was approved, and it does not grade the oak.
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?
Planning and building-regulations papers are the solicitor’s file. The survey’s file is condition: rot at the feet, a failed joint, a roof covering that is now heavier than the frame, insulation that hides the timber. Approved Document A is England’s structural guidance for building work. It is not a retrospective certificate. Spray foam or boarded linings can hide the very members you need to see.
A structural engineer is the person who comments on whether a truss can carry a floor, if the survey says that is unclear. There is no RICS price for that opinion. Do not sandblast the timbers as a repair. Do not assume a barn is non-standard concrete construction. It is a conversion until someone shows a different frame.
What should you ask your surveyor?
- Which trusses were visible, and which were lined over?
- Did you see cuts, rot, or only the covering?
- Which papers are outside your inspection?
What are the typical next steps?
- Ask the solicitor for the conversion approvals.
- Do not hide the trusses with new linings before they have been seen.
- If the feet are rotten, that is a repair. It is not a reason to condemn the whole frame unseen.
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 a steel portal frame the same as an oak truss?
No. Name the frame. The survey should not call steel oak, or oak a modern truss.
Does a pretty interior mean the truss feet were dry?
No. The feet are often at the wall, behind finishes. Read the limitations.