Damp and moisture meters
Render is hollow at the base of one wall and sound at the top. Why should the hollow band not be read as subsidence?
The hollow render at the base of this one wall should not be read as subsidence. A hollow coat is a comment on the render, not on the foundations. The top of the same wall was sound, so the hollow band is local. One patch is not the whole elevation, and it is not movement of the house. Do not invent a price or a lifespan for the masonry behind it. Treat the band as render to investigate.
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 hollow sound at low level can come from a coat that has lost its bond, or from salts or moisture held behind it. Those are reasons to investigate the surface. They are not proof of rising damp, and they are not a pattern of cracking in the wall. The survey noted a hollow band. It did not measure the building moving.
Subsidence is read from the ground, the cracks and the history of the site, not from a hollow knock on a render coat. A sound top and a hollow base do not supply that reading. Keep the comment on the render. If the coat needs opening, agree that separately, and do not let the word hollow move onto the foundations.
What should you ask your surveyor?
- Was the hollow sound limited to the base, with the render above it still firm?
- Did you see cracking or leaning of the wall, separate from the hollow coat?
- Are you commenting on the render, and not on foundation movement?
What are the typical next steps?
- Describe the hollow band as render on that part of the wall only.
- Do not relabel the hollow render as subsidence of the house.
- Do not invent a repair price or a lifespan for the bricks behind 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
If the render is hollow, has the wall behind it cracked?
Not from this finding alone. Hollow render is the coat you can tap. The survey has not said the masonry or the foundations have moved.
Does hollow render at the base prove rising damp?
No. It is a reason to investigate the coat and whatever is held behind it. It is not, by itself, proof of rising damp.