Wall ties and cavity insulation

What is a weep hole, and why is it not a failed cavity wall tie?

A weep hole is a small opening, often in a perp joint, left so water in a cavity can drain out above a window, a door or at the base of a wall. It is supposed to be there. A failed wall tie is a different thing: metal in the cavity that no longer holds the two leaves together. A home survey should not call a clear weep a tie failure.

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?

Ties are hidden. The usual visual clues are horizontal cracks in regular courses, a bulging outer leaf, or a pattern a surveyor has learned to suspect. A neat open joint every so often along a lintel is a weep, not that pattern. The Energy Saving Trust’s cavity advice is about whether a cavity is fit to fill. It is not a tie test, and filling over working weeps can block the very path the joint was left for.

If weeps are blocked with mortar or render, say that. Blocked drainage of the cavity is a moisture comment. It still is not a borescope inspection of the ties. A tie survey, if you need one, is a separate instruction. There is no RICS price for it. Do not repoint every weep shut because the wall looks unfinished.

What should you ask your surveyor?

Are you describing weep holes or cracks in the bed joints?
Are the weeps open, or filled?
Have you inspected the ties, or only the face?

What are the typical next steps?

Do not seal weep holes as decoration.
If the survey suspects ties, ask for the clues, not a guess from an open joint.
Keep cavity insulation and tie condition as two questions.

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

Is a cavity tray the same as a weep?

No. The tray catches water. The weep lets it out. The survey may see neither.

Does an open weep mean the wall is leaking?

Not by itself. An open weep is often the design. Staining pouring from it is the comment.