Windows, doors and glazing
If a uPVC window frame is still square and firm, does a misted sealed unit mean the whole frame should go?
No. Mist between the panes means the edge seal of that glass unit has failed, and a uPVC frame that is still square and firm can remain serviceable, so the failed part is the glass rather than the plastic. A home survey does not measure the frame or order a new window, and replacing every frame because one unit has misted is a choice rather than what the misting proves. A failed seal is not rot, and it is not automatically a condition rating 3 for the whole elevation.
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?
Condition ratings describe what the surveyor thinks needs repair and how urgent it is. A single failed unit is often a replacement of that glass in the existing frame, which a glazier can confirm once they see the beads and the spacer. Rating 3 is for something serious or urgent, with quotations before you are legally committed. It is not the automatic label for misted glass, and rating 2 is not a price. The survey should say whether the frame was distorted, cracked or firm. Plastic does not rot in the way timber does. Do not import a timber-rot sentence.
Several misted units raise a larger glazing bill and still do not, by themselves, condemn sound frames. Ask which openings are misted and which frames are out of square. There is no national window price in the survey. A quote should separate glass from frames. Missing paperwork for the original installation is a solicitor’s question. It does not make a firm frame defective, and it does not make a clear unit misted. The survey has not tested the locks.
What should you ask your surveyor?
- Which units are misted, and which frames are still firm?
- Is any frame distorted, or only the glass?
- Are you rating the seal, the frame, or both?
What are the typical next steps?
- Ask a glazier for a glass-only price where the frame is firm.
- Do not replace the elevation because one unit has failed.
- Keep certificates with your solicitor. They do not change the mist.
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
Is mist in a timber window the same?
The failed seal is the same idea. The frame may also be rotten, which uPVC is not. Ask about the frame material you actually have.
Does a failed unit mean the cavity between the panes can be cleaned?
No. The seal has gone. Cleaning the inside of a failed unit is not a repair. The unit is replaced or the window is replaced. The survey does not choose which.