Roofs and flat roofs
The survey states an assumption about insulation depth because the loft was not entered. Is that assumption a measurement?
No. The assumption is not a measurement. The survey states an assumption about insulation depth because the loft was not entered, so the quilt was not seen and was not measured. An assumption is a stated stand-in so the report can be read with that limit in mind. It is not a depth taken with a tape. If the loft is later opened, the real depth may be different. The report is telling you the figure was not observed. Do not quote it as a taped thickness.
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?
Surveyors sometimes state an assumption where a space is closed, so the reader knows the report is not pretending the void was inspected. Insulation depth affects how you read energy comments, and a guessed or standard figure is not the quilt in this roof. Hatsches stick, ladders are missing, or belongings block the way. Whatever the reason, not entered means not measured. The assumption keeps the prose complete. It should be read beside the limitation, not lifted into a specification as if the ruler had been there.
Ask the seller for access and, if it matters, have the depth measured once the loft is open. Tell a lender or an assessor that the survey figure is an assumption, not a measurement, if they ask where it came from. The solicitor can note the limit. Do not let a later form copy the assumption into a box marked measured. When someone does enter, the finding replaces the assumption. Until then the depth is unknown, and the report has already said so.
What should you ask your surveyor?
- Is the stated insulation depth a tape measurement?
- Why was an assumption used instead of a figure from the loft?
- Can the assumed depth be quoted as observed thickness?
What are the typical next steps?
- Treat the depth as an assumption, not as a measurement.
- Do not copy it into a form as a taped figure.
- Measure the quilt if the loft is later opened.
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
Can you give the assumed depth to a lender as a measured thickness?
No. The loft was not entered, so nobody measured the insulation. The survey labels the figure as an assumption. Passing it on as a tape result would misstate the report. Tell the lender the depth was not observed. If they need a real figure, the loft has to be opened and the quilt measured. Until then there is no measured thickness to give.
What should replace the assumption if the hatch is opened later?
A real measurement, taken in the loft, should replace it. The assumption exists only because the space was not entered. Once the quilt can be seen, the depth is whatever is there, which may not match the stand-in. That later look is a new observation. It is not a correction the original assumption already contains. Record the measured depth separately.