Wall ties and cavity insulation
Cavity fill is claimed in a random-stone wall that may not have a cavity. What has the survey not confirmed about the construction?
The survey has not confirmed that a cavity exists, that it was filled, or that the fill is the product claimed. Random stone is often solid or of uncertain build-up, with facing stones, mortar and rubble rather than two leaves and a clear gap. A seller's claim of cavity insulation does not create that gap. This visit did not open the wall, use a borescope or sample any fill. Stone outside and plaster inside do not show the core. The report can note the claim and the wall it could see. It has not confirmed the construction.
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?
Thick stone can look as if a cavity ought to be there when the wall is simply solid. Paperwork sometimes names cavity fill on a house that was never a cavity house, or describes material pumped into voids that are not a proper gap. The survey did not measure leaf thickness and did not take a core. A damp patch inside might relate to the stone, to rain on the face, or to material now holding water. None of those causes has been separated. The claim remains a claim.
Ask the solicitor for any insulation guarantee, the installer's description of the wall and any photograph from the time of the work. Those papers show what was asserted. They are not an opening of the wall. A lender may ask what construction the survey actually found. The honest reply is that a cavity and the fill are unconfirmed. If the build-up must be proved, that is a borescope or an opening agreed in advance, not a conclusion this visit already reached.
What should you ask your surveyor?
- Which sentence records a claim of fill, rather than a cavity the surveyor saw?
- Is the wall described as random stone, solid, or of unknown build-up?
- Were injection holes noted, or only a story that the wall had been filled?
What are the typical next steps?
- Ask the seller for the insulation guarantee and the wall description written on it.
- Do not tell the lender this stone wall is a confirmed filled cavity.
- If the build-up matters, instruct an opening or borescope this visit did not do.
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
Does an energy certificate that assumes filled cavities settle the construction?
No. An energy certificate uses standard assumptions and declarations. It does not core a random-stone wall or prove a cavity was there to fill. A modelled improvement can be printed for a wall that is solid. The survey has not treated that certificate as evidence of how this house is built.
Could the fill sit in a later inner leaf rather than in the stone itself?
It could, and the survey has not confirmed that either. A stone face sometimes has a later block leaf and a gap, and sometimes it does not. Without an opening or a borescope, the pack cannot choose between those builds. Keep the uncertainty. Do not draw a cavity that nobody saw.