Wall ties and cavity insulation
Why can a hard cement render be a problem on a soft brick or stone wall?
Because the render can trap moisture in a wall that used to breathe, and when it cracks, water gets behind a sheet that cannot let it out. A home survey sees cracks, hollowness and blown patches. It does not test the mortar mix in a laboratory, and it should not call every render coat a wall-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?
Older solid walls were often finished in lime. A later cement coat is a different material. The surveyor may suspect that from the look and the age. Suspicion is not a specification for hacking it all off. Hollow areas and cracks that let rain in are the defects to quote. Sound render that is only unfashionable is not a rating 3.
The Energy Saving Trust says walls should be in good condition before cavity insulation, which is a different wall. On a solid wall, insulation is a separate design. Do not combine “remove render” and “inject beads” in one guess. There is no RICS price for render removal. A mason should say how far is hollow.
What should you ask your surveyor?
- Is the render hollow, cracked, or only hard?
- Is the wall solid or cavity?
- Are you seeing salts or just hairline crazing?
What are the typical next steps?
- Ask a mason to tap the hollow areas and quote those, not the whole street elevation, unless they explain why.
- Do not insulate over cracked render.
- If the house is listed, ask about consent before you specify a new coat.
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 as a smooth cement render?
It is a different finish. It can still crack and trap water. The survey should describe what is there.
Does paint on render make it worse?
A film can slow drying. The survey cannot prove that from one visit. It can note blistered paint over a hollow patch.