Windows, doors and glazing
The window board is soft and the sealed unit above it is clear. Which material is damp, and which has not failed?
Only the soft window board is the damp material in that note. The sealed unit above it is clear, so the glazing has not failed. Soft timber has been wet enough to lose its firmness. A clear unit has no mist between the panes, and the seal is not the failure being reported. Do not swap the two. The board can be wetted by moisture running off sound glass, or by the sill, without the unit having failed. The visit identifies the board. It does not condemn a pane that is still clear.
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?
Boards sit where cold glass can shed water into the room. That wetting can soften the timber and blister the paint while the unit stays sealed. The check on the unit is the cavity between the panes, and here it is clear. The check on the board is whether it is soft, and here it is. Those results point at the timber. Replacing a clear unit would answer a defect that was not found, and it would leave the soft board where it is.
A joiner can repair the board and look at the sill and the frame beneath it, which may be the source and may be sound. Ask them to say which. If they also want the unit changed, ask them to show mist or a broken pane the survey did not find. Keep the damp note on the window board until that timber is dealt with. Clear glass stays off the defect line. The failed material is the board.
What should you ask your surveyor?
- How soft is the window board, and is the sill or the frame soft as well?
- Is the sealed unit clear between the panes, including at the edges?
- Which material are you calling damp, and which has not failed?
What are the typical next steps?
- Repair the soft window board rather than the clear sealed unit above it.
- Ask the joiner to check the sill and the frame before the glass is blamed.
- Do not replace the unit unless mist or a broken pane is actually found.
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
Has the double-glazed unit failed because the board under it is soft?
No. The unit is clear, so the seal has not failed. The damp material is the window board, which is separate from the pane above it.
Can a clear unit still wet the board beneath it?
Yes. Sound glass can shed moisture onto the board. That does not put mist in the unit, and it does not turn a clear pane into a failed seal.