Outbuildings and conservatories
The conservatory base covers an air brick of the house. Has the subfloor ventilation that remains been judged adequate?
The subfloor ventilation that remains has not been judged adequate. The conservatory base covers an air brick of the house, so that inlet is bridged or blocked by the new base. Other air bricks, if they exist, were not measured as a system, and the underfloor void was not proved still vented. Losing that opening is clear. Whether what is left is enough was not judged, because the void and the remaining path were not fully seen. The survey records the covered brick. It does not pass the subfloor.
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?
Suspended timber floors rely on air moving through the void so moisture does not sit under the boards. Air bricks are the inlets and outlets for that path. When a conservatory base is built across one of them, that route stops at the new wall. Adequacy depends on how many bricks remain, whether they are opposite each other, and whether sleeper walls still let air through. None of that balance was calculated. A single covered brick is a defect in the ventilation path. It is not a whole-void test.
Ask the solicitor whether the conservatory had approval papers that dealt with the air brick. A builder can expose the brick and say what ventilation is left, if you instruct that. The survey has not made that opening and has not called the joists decayed or sound. Tell a lender one air brick is covered and the rest of the system was not judged adequate. Do not assume the floor is safe because the rooms above felt dry.
What should you ask your surveyor?
- Has the remaining subfloor ventilation been judged adequate?
- Is the air brick under the conservatory base still a working inlet?
- Was the underfloor void fully seen and measured as a system?
What are the typical next steps?
- Treat the covered air brick as a lost inlet, not as a passed void.
- Ask the solicitor for any approval papers for the conservatory.
- Instruct a builder if the remaining ventilation must be judged.
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 covering one air brick prove the whole void is wet?
No. It proves that one inlet is covered. Wetness in the void was not shown, and the joists were not fully seen. Moisture may or may not be building under the floor. The survey has not judged the ventilation that remains and has not diagnosed rot. The covered brick is the finding. Decay, if any, would need a proper look into the void.
Were the other air bricks counted and traced under the floor?
No. They were not counted as a system and were not traced past sleeper walls. The survey saw the conservatory base over one air brick. Remaining bricks, if noticed at all, were not used to judge adequacy. A count and a void inspection would be further work. This report does not contain that judgement.