Damp and moisture meters
No cavity tray is visible over the extension abutment. Has the survey opened the wall to prove it is missing?
No. The survey has not opened the wall to prove the tray is missing. No cavity tray is visible over the extension abutment, which means none could be seen at that junction. A tray can sit inside the cavity and show only as weepholes, and those too can be hidden by the abutment. Not visible is not the same as proved absent by opening up. The report records what could not be seen. It has not cut the wall to confirm a void where a tray should be.
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?
Where an extension meets a cavity wall, a tray is meant to catch water running down the cavity and throw it outside. If you cannot see the tray or its outlets, you cannot yet say it was never built. Render, cladding or the extension roof can mask the usual clues. The surveyor did not open the leaf. Any damp at the junction, if noted, is a separate observation and still does not prove the tray’s absence by itself. The limit is a hidden detail left unverified.
Ask the solicitor for any drawings or building-control photos that show a tray at this abutment, and keep them apart from the visual note. If staining suggests water is getting past the junction, a specialist may need to open the wall under a proper instruction. The home survey has not done that opening and has not proved the tray missing. Do not hack off render to settle it on a viewing.
What should you ask your surveyor?
- Where is the abutment, and what was looked for there?
- What coverings might be hiding a tray or its outlets?
- Does the report say the wall was opened?
What are the typical next steps?
- Read not visible as not proved absent.
- Ask for any drawings that show a tray at the junction.
- Do not open the wall on the back of this note.
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
Do blocked weep holes prove the tray was never installed?
No. Weep holes, blocked or missing, are a clue about outlets. They do not prove a tray was never built, and this visit did not open the wall. No cavity tray is visible over the extension abutment. That is a limit of what could be seen. Absence stays unproved until the junction is properly opened by someone instructed to do it.
Was a damp meter used to prove the tray is missing?
A meter, even if one was used on the surface, would not see a tray inside the cavity, and the survey did not open the wall. Moisture at a junction can have several causes. The report’s point is that no tray is visible. It has not proved the tray missing by instrument or by opening up.