Damp and moisture meters
What should you ask if the air bricks under a suspended timber floor are blocked or buried?
Ask whether the surveyor could see ventilation to the void under the floor, and whether the boards themselves were inspected. Blocked air bricks can leave that void stale and damp. They are not, on their own, a failed damp-proof course in the wall, and a Level 2 does not lift fitted floors to prove the joists.
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?
Older houses often have a timber ground floor over a shallow void. Air bricks are there so moisture from the ground can leave instead of sitting under the boards. Soil, a new patio or a painted-over grille can shut that path. The symptom inside may be a musty smell, blown skirtings or soft boards near an external wall, which a damp meter will also notice.
The Property Care Association’s advice on timber is that moisture has to be dealt with, not only the wood. Opening one board tells you about that bay, not about every joist. A home survey records the limit. If the rating says the floor matters before you commit, ask for a floor inspection with a written scope. Do not budget a whole new floor from a buried air brick alone.
What should you ask your surveyor?
- How many air bricks could you see, and were any buried or sealed?
- Did you lift any boards, or is the void not inspected?
- Is the recommendation ventilation, or a wider check of the joist ends?
What are the typical next steps?
- Do not screed over the void or block the grilles to stop a draught.
- Clear soil from grilles only if you can do it without undermining the path. Ask before you dig against a wall.
- If the report rates the floor, get a timber inspection rather than a spray quote.
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 air bricks the same as a damp-proof course?
No. The course is in the wall. The air bricks vent the space under the floor. A house can have one working and the other blocked.
Will a laminate floor prove the boards are dry?
No. A finish hides the boards. It is not an inspection of the void.