Wall ties and cavity insulation

Does an invoice for cavity extraction prove the surveyor inspected the ties?

No. An invoice shows that someone billed for removing fill, and perhaps for putting fill back, but it does not show that your surveyor saw the ties or that every bay was checked. The home survey inspects what it inspects. A contractor’s bill is not that inspection, even if the date is recent.

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?

Extraction jobs are sold to take failed or slumped insulation out of a cavity, sometimes before new fill or before tie work. The paper might be a quote, a paid invoice, or a guarantee. Read the verbs. “Extracted and refilled” is not the sentence “ties tested and replaced”. The Energy Saving Trust still expects the wall itself to be suitable before fill goes back. A bill does not become a boroscope report because it has a letterhead. Your surveyor may never have seen the open cavity. They should not be asked to sign the invoice as if they had.

Ask the seller who did the work and for any photographs or guarantee that came with it. Then ask the surveyor, separately, what they could see on the day: new drill patterns, old cracks, spilled fill, or a wall that looks undisturbed. If they could not see inside, the limitation stands beside the invoice, not under it. Do not tell a lender the ties were renewed because extraction was paid for. If the wall still has the crack pattern that worried the surveyor, the invoice has not answered it.

What should you ask your surveyor?

Did you see the cavity, or only the outside of a wall that may have been refilled?
Does anything in your inspection confirm or contradict the invoice?
Please state that the invoice is not your tie inspection.

What are the typical next steps?

Put the invoice with the legal papers, not into the survey as if it were a finding.
Read whether it mentions ties at all.
If the survey still suspects tie failure, instruct a tie inspection rather than waving the bill.

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 a guarantee on the invoice cover the ties?

Only if it says so. Many cover the fill they installed. Read the exclusions before you rely on it.

Can you ignore cracks because the cavity was extracted?

No. Cracks are still on the wall. Extraction does not point them, and it does not date them.