Wall ties and cavity insulation
Rigid insulation shows in the cavity at a window reveal where the frame was replaced. What fill of the rest of the cavity was not seen?
The fill of the rest of the cavity was not seen. Rigid insulation shows in the cavity at a window reveal where the frame was replaced, which tells you a board is present at that opening. It does not tell you whether the same board, a different fill, or an empty cavity continues past the reveal. The survey has recorded the exposed edge. It has not opened the wall elsewhere, and it has not described a whole-house insulation type from one cut reveal.
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?
Replacing a window often cuts back the jamb and shows whatever was in the cavity at that point. A rigid board at the reveal may be a closer piece, a partial fill, or the edge of a wider system. From that edge you cannot see the cavities above, below or along the wall. Energy Saving Trust material on cavity insulation is not a survey of this wall. The home survey did not use a borescope, and it did not infer a full fill from a single board.
If you need to know how the rest of the cavity is filled, that is a separate inspection which can see beyond the reveal. Tell the solicitor the report only describes insulation where the frame was replaced. Do not assume the house has been fully insulated, and do not assume the cavities are empty. The survey has not seen those lengths, so neither storey should be written up from the board at this window.
What should you ask your surveyor?
- Where exactly did the rigid board show, and was it only at the replaced frame?
- Did you see any other cavity fill away from that reveal?
- Have you left the rest of the cavity undescribed?
What are the typical next steps?
- Limit the insulation note to the board seen at the reveal.
- Do not describe the rest of the cavity as filled or empty.
- Arrange a further look only if the hidden fill must be known.
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 board is dry, is the whole cavity dry?
No. A dry edge at one reveal says nothing about cavities you did not see. Moisture elsewhere, or none, was not observed. The survey recorded the board where the frame was replaced. It has not graded the rest of the fill.
Does a new window frame mean the cavity was fully upgraded?
No. A new frame shows recent window work. It does not prove the rest of the cavity was insulated, and it does not name the product used beyond the board at the reveal. The survey has not seen that wider fill.