Damp and moisture meters
Can a failed cavity tray above a window show as damp only after driving rain?
Yes. A cavity tray is meant to catch water that crosses the cavity above an opening and lead it outside. If it is missing, blocked or torn, the stain indoors can appear after wind-driven rain and then fade. A dry day of inspection does not prove the tray is sound.
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?
Surveyors see the symptom if it is there on the day: staining over a window, perished paint, or a damp patch on the reveal. They often cannot see the tray itself without opening the wall. The honest report says what was visible and what was not. It should not convert a possible tray fault into a diagnosis of rising damp.
The same stain can come from failed sealant, a cracked sill or a gutter above. Ask which of those the surveyor could check from the ground or from a ladder, and which would need a bricklayer or a cavity specialist. There is no national price for replacing a tray. Ask a contractor who has seen the opening.
What should you ask your surveyor?
- Was the staining above the opening, at the reveal, or at skirting level?
- Could you see weep holes, a tray, or only the inner decoration?
- Did the inspection follow wet weather or a long dry spell?
What are the typical next steps?
- Photograph the stain and note the weather. A faded patch is still evidence.
- Do not sand and repaint as the repair. Paint is not a tray.
- If you need certainty before exchange, ask for an inspection that will look for the tray, and put that scope in writing.
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
Are weep holes a defect?
No. Open weep holes are how many trays drain. Blocked or absent weeps are the thing to ask about.
Does a cavity tray replace a wall tie?
No. A tray handles water at an opening. A tie holds the two leaves together. They fail in different ways and they are not one quote.