Wall ties and cavity insulation
What is a cavity tray, and how is it different from a wall tie?
A cavity tray catches water inside the cavity and leads it outside, usually above a window, a door or a roof abutment. A wall tie holds the two leaves of brick or block together. One deals with water. The other deals with how the wall stands up. They are not alternative names for the same thing.
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?
A failed tray shows as damp over an opening or at an abutment. Failed ties show as cracking, bulging or rusty bed joints. A report that mentions both is describing two mechanisms. A quote that “sorts the cavity” without saying which one is not a specification you can compare.
Ask the surveyor which evidence points to the tray and which points to the ties. Then instruct the matching investigation. A bricklayer may deal with a tray. A tie specialist deals with ties. Some firms do both, but the quote should still separate them. Prices are theirs to give after they have seen the wall.
What should you ask your surveyor?
- Which signs are tray signs, and which are tie signs, in this report?
- Could you see weep holes or a tray, or only the internal stain?
- Do you want one specialist or two?
What are the typical next steps?
- Split the next instructions on paper so you do not pay twice for the same visit by accident, or miss one of the defects.
- Do not accept a damp-proof injection as the repair for either a tray or a tie.
- Read the driving-rain tray question if the stain is only over a window.
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
Can a wall tie double as a tray?
No. Some ties are shaped, but they do not replace a tray over an opening. If the report uses both words, keep both meanings.
Are weep holes optional?
Where a tray is supposed to drain, blocked weeps stop it working. Absent weeps may mean you cannot see a tray. Ask, rather than poking them shut.