What might be happening
Blocked, buried or bridged air bricks may restrict cross-ventilation, particularly under older timber floors.
A timber floor can look perfectly ordinary from above while the damage is hidden underneath. The first job is to work out whether the boards themselves are affected or whether the joists and their supports need attention.
What you can look for
Check external ground levels, vegetation, extensions and whether air can travel across the whole subfloor void.
You do not need to start taking the building apart yourself. If access is difficult, ask the person inspecting it to explain what needs to be opened up and why. Photographs of hidden defects are useful, especially when you are comparing quotations.
Putting it right
Clear obstructions and seek suitable ventilation improvements while also addressing damp ground, leaks or wet masonry.
Be wary of a quotation that deals only with the damaged wood and says nothing about the water or building defect behind it. Once the cause has been dealt with, the remaining timber can be checked and the necessary repairs planned.
When to call someone in
Do not open or alter ventilation arrangements without checking for services and site-specific requirements.
A carpenter or joiner may be right for a local timber repair. If the problem involves a leak, you may need a plumber or roofer first. Where supporting timbers have moved, sagged or seriously weakened, get advice from someone qualified to assess the structure.
Questions worth asking
- Is the problem in the floorboards, the joists or where the joists sit in the wall?
- Can you show me the extent of the damage before any sound timber is removed?
- What caused it, and how will that cause be put right?