Roofs and flat roofs
The apron flashing under a roof window is dressed so water runs back toward the frame. What weather path is that, distinct from the glass itself?
The weather path is rain turned back toward the roof-window frame by the apron, which is separate from the glass. The apron flashing is dressed the wrong way, so water running down it is sent toward the frame instead of being shed onto the tiles below. The survey can see that dressing. It has not tested the glass unit, and it has not decided that the sealed pane has failed. The path is the flashing, not the glass.
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?
An apron is the flashing that sits under a roof window and laps onto the covering below, so rain leaves the frame and continues down the roof. Dressed the wrong way, the upstand or the lap turns that water back. It can track under the frame or sit against the timber. That is a weathering defect in the metal or the lead, whichever the apron is. Mist in the glass, if any, would be a different defect. This note does not depend on the pane.
Ask a roofer to redress or replace the apron so water sheds onto the covering, and to check the frame and the trim the water has been running toward. Keep that separate from any glass replacement. Tell the solicitor the survey has identified a flashing path, not a failed unit. Do not buy a new sealed pane on the strength of this dressing alone. The glass was not the finding.
What should you ask your surveyor?
- Is the weather path the apron dressed back toward the frame?
- Did you keep that path distinct from the glass?
- Was the sealed pane left untested?
What are the typical next steps?
- Describe the apron as the weather path, not the glass.
- Ask a roofer to redress the flashing so water sheds outward.
- Do not replace the pane solely because the apron is wrong.
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 glass is clear, can the apron be ignored?
No. Clear glass means you are not looking at a misted unit. The apron is still dressed so water runs back toward the frame. That path is independent of the pane. The weather path is the flashing, and the survey has not cleared it.
Does water staining on the reveal prove the glass has failed?
Not from this note. Staining on the reveal fits water from the wrongly dressed apron. The survey has not tested the glass, and it has not called the unit failed. A mark inside can come from the flashing without the sealed pane having failed.