Wall ties and cavity insulation
A single core hole shows a butterfly tie. Why is that one tie not a survey of every tie in the wall?
Not every tie. One butterfly tie in one core hole is that tie, at that hole, and nothing wider. A core is a small opening. It can show the type of the tie you happened to meet, and perhaps the state of that one piece of metal. It cannot map the spacing, the condition, or even the presence of the ties you did not core. The rest of the wall is unopened. Do not write a sentence that turns one butterfly into a survey of every tie. Say what the hole showed, and stop there.
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?
Butterfly ties are a wire shape people recognise in older cavities. Recognising one does not tell you that the wall was tied throughout with that pattern, or that the others are sound, rusty, or missing. A single hole also cannot say the cavity was clear, or that fill would be suitable. The Energy Saving Trust's decision about cavity fill looks at the wall as a wall, not at one lucky glimpse of metal. Keep the core as a sample of one.
If more holes were drilled, each hole is still only its own hole. Do not average them into a claim that every tie matches the first. If only one hole exists, the limit is stricter. The home survey, unless it commissioned that opening, may simply be reporting a hole someone else made. Either way, quote the location. A lender or a buyer should not be told the elevation has been tie-surveyed because one butterfly was photographed.
What should you ask your surveyor?
- Where was the core, and was the butterfly tie the only one seen?
- What could you not say about ties away from that hole?
- Who made the hole, and was it part of your inspection?
What are the typical next steps?
- Limit the comment to the butterfly tie in that one hole.
- Do not describe it as a survey of every tie.
- Ask for a proper tie investigation if the whole wall needs one.
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 one butterfly tie mean the wall is adequately tied?
No. One tie in one hole is not a survey of every tie, and it does not show the wall is adequately tied.
If the tie looked rusty, have all the ties failed?
No. Rust on the tie you can see stays with that tie. The others were not in the hole and were not inspected.