Wall ties and cavity insulation
Nothing on the visit sampled cavity bead, opened a buried air brick or tested the underfloor void the bead may have reached. What has to stay undecided?
Whether cavity bead has blocked the underfloor void stays undecided. Nothing on the visit sampled the bead, opened a buried air brick or tested the void the bead may have reached. Bead is a cavity-fill material. An air brick is the vent path to the floor void. If fill has spilled into that path, the survey has not shown it. The report notes the possibility and the limits. It has not inspected the void and it has not tested wall ties.
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?
Cavity beads are blown into the wall. They can escape through gaps, open perpends and air bricks that were meant to ventilate the floor, especially if the brick was already low or later buried by paths. A buried air brick may be blocked by soil alone, by bead, or by both, and the visit did not dig it out or enter the void. Timber moisture and sleeper walls were not inspected through that route. The spill remains a possibility, not a finding.
Ask the solicitor for the cavity-insulation guarantee and any note of air bricks or vents. A specialist can look in the cavity and, separately, the floor void can be inspected if access exists. Neither happened here. Tell a lender the bead was not sampled and the buried air brick was not opened. Do not state that the underfloor timbers are dry or that the ties were checked. The survey did not reach either.
What should you ask your surveyor?
- Was cavity bead left unsampled?
- Was the buried air brick left unopened?
- Has the underfloor void the bead may have reached stayed untested?
What are the typical next steps?
- Leave bead, the buried air brick and the floor void undecided.
- Ask the solicitor for the cavity-insulation guarantee.
- Do not tell a lender the ties or the void were checked.
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 bead insulation prove the wall ties are stainless?
No. Fill and ties are different. Bead can hide ties and can make a later tie inspection harder, but this visit did not sample the bead and did not test ties. A guarantee for insulation is not a tie certificate. Ask the solicitor which document, if any, actually names the ties.
Is a painted air brick on the wall above the path the same vent?
Not necessarily. The brick you can see may serve a room or a cavity tray, while the underfloor vent may be the one now buried. The survey did not open the buried brick and did not test the void. Count only the vent the report actually identifies. Do not let a visible grille stand in for the one that may be blocked.