Timber decay and woodworm
What can a survey say about a sleeper wall if the surveyor could not crawl the floor void?
It can say the void was not entered, so the sleeper wall, the plates on it and the joist ends were not inspected. That is a limitation, not a pass, and it is not a finding that those timbers have failed. A sleeper wall is the low wall that holds up joists under a suspended floor. If nobody reached it, nobody has assessed it.
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 often cannot crawl a void because the clearance is low, the access hatch is too small, or there is no hatch at all. The Property Care Association links wet rot and dry rot to timber that stays damp. Joists and wall plates bearing on a damp sleeper wall are a known place for that, but only if someone can see or properly investigate them. A comment that the subfloor was not inspected does not invent rot in every bay. It also does not let you assume the plates are sound because the carpet upstairs feels firm.
Ask where access was attempted and why it stopped. Ask whether air bricks were blocked, because that is something visible outside even when the crawl was impossible. Blocked ventilation is a moisture risk the PCA would want dealt with. It is still not a view of the sleeper wall. Do not pay for a whole-house timber spray quoted from “not inspected”. If you need the void seen before you commit, agree an opening with the seller and a person equipped to enter safely. The home survey has already told you it did not do that crawl.
What should you ask your surveyor?
- Why could you not reach the sleeper wall, and was there any hatch?
- What could you see from outside, such as air bricks, that the crawl would not have changed?
- Please confirm you are not reporting the plates as either sound or rotten.
What are the typical next steps?
- Do not treat “not inspected” as a clean floor.
- Do not treat it as a reason to inject every wall and spray every joist.
- If the void must be seen, arrange access. Do not pretend a torch at the hatch was a crawl.
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 firm floor above mean the sleeper wall is fine?
No. Carpet and boards can feel firm while a plate at the far end is soft. Unseen means unseen.
Can the surveyor condemn the sleeper wall without entering?
They can report a risk if the outside evidence is strong, such as no ventilation and a wet wall. They still have not seen the timber. The sentence should stay that cautious.