Timber decay and woodworm
Air bricks have been painted over so the holes are closed. What floor void has lost that air path?
The void under the suspended ground floor has lost that air path. The air bricks are painted over and the holes are closed, and those holes are what let outside air through the wall into the space under the boards. With the holes shut, the path is blocked. The survey has recorded painted air bricks. It has not measured moisture in the joists and has not called the floor decayed. Approved Document F is the guidance on ventilation. This visit has not applied it as a test of the void, and it has not proved the timbers are damp.
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?
Air bricks are built into the outer wall so air can cross the space under a suspended timber floor. That movement is there to keep the void from staying stale and humid. Paint that fills the holes turns the brick back into solid wall. The void inside those bricks is the space that loses the path: joists, sleeper walls and the oversite. The survey does not have to declare the joists rotten in order to record the blockage. Closed holes are the finding.
Tell the solicitor the air bricks to the ground-floor void are painted shut. Putting an air path back is a building job for someone instructed to do it, and the survey has not specified the method. Approved Document F deals with ventilation. The home survey has not certified this floor against it. Do not read closed holes as proof the joists have already decayed, and do not read them as harmless because no soft board was seen. The lost path is what the note establishes.
What should you ask your surveyor?
- Which air bricks are painted so that the holes are closed?
- Is the lost path the one into the suspended ground-floor void?
- Did you leave the joists in that void unmeasured?
What are the typical next steps?
- Treat the closed air bricks as a lost path into the floor void.
- Do not call the joists decayed from this note alone.
- Ask a builder to restore the air path. This report is not the specification.
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
If the floorboards feel firm, has the void kept its air?
Firm boards are the surface you walk on. They do not reopen holes in air bricks that paint has closed. The underfloor void has still lost that path. The survey has not measured the joists and has not called them decayed. Firmness underfoot is not the ventilation that is missing.
Does one open brick somewhere else replace the painted ones?
Not on this note. The bricks that were painted over have closed holes, and the void they served has lost those paths. Another brick left open, if there is one, was not assessed as a whole substitute system. The survey has not calculated how much air still moves. The painted bricks remain closed.