Wall ties and cavity insulation

What should you ask if render or paint covers the base of a cavity wall?

Ask whether the weep holes and the damp-proof course are still visible, or whether the coating has buried them. Render taken down over the open joints can block the cavity’s way of draining and can bridge the course. That is a moisture detail. It is not, by itself, a wall-tie failure. A home survey sees the coating. It does not remove it.

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 cavity wall is meant to break the path of rain. If the coat seals the weeps and carries damp across the base, the inner leaf can stain even though the ties are sound. The Energy Saving Trust wants a cavity wall to be in sound condition before it is filled, and a coated wall is harder to judge. The Property Care Association’s damp advice is to find the defect, not to name a product from the pavement.

Cutting render off is a builder’s job, agreed with the seller if you do not yet own the house. There is no RICS price for it. If the survey also sees horizontal cracks above the render line, that is the tie question, kept separate. Do not hack the coat off on a viewing.

What should you ask your surveyor?

Could you see weep holes, a damp-proof course, or only the coating?
Is there staining inside at the same level?
Are you commenting on the coating, the ties, or both?

What are the typical next steps?

Do not seal the base further with more render.
If weeps are buried, ask a builder what it would take to open them, not for new ties by default.
Keep a tie inspection for the day the cracks justify it.

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 pebbledash the same comment?

It is another coating. It hides the joints. It is not a tie test and not a damp-proof course.

Does paint on brick always trap water?

Not always. The comment is when the paint, the ground or the render bridges the course or seals the weeps. Say which.