Wall ties and cavity insulation
Cavity insulation is visible at the eaves with the cap missing, and the loft quilt is dry. What path for rain does that open cap still leave?
Not closed by a dry quilt. Cavity insulation visible at the eaves, with the cap missing, still leaves a path for rain at the top of the cavity. The open cap is an entry. Water can reach the insulation and the head of the wall there even though the loft quilt felt dry on the day. Dry quilt means the quilt was dry. It does not seal the cap, and it does not prove rain never uses that route. The survey should describe the missing cap as a rain path. It should not cancel that path because the quilt was dry.
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?
At the eaves the cavity meets the roof space. A cap or closer is what keeps the top of the filled cavity from standing open to weather blown under the tiles. If the cap is missing and the insulation is visible, the fill itself is sitting in that opening. Rain does not have to soak the quilt to have a route onto that insulation and down the cavity. Today's dry quilt is a snapshot of the quilt, not a test of the next wet wind.
Do not call this a wall-tie failure. Nothing in a missing cap measures a tie. It is also not proof that every filled wall has gone wrong. The Energy Saving Trust treats exposure and a suitable cavity as part of the filling decision. An open eaves detail is a defect in that detail. Ask which elevation, whether the cap is missing in a run or at one spot, and what the surveyor could see. Keep the dry quilt as a separate, smaller fact.
What should you ask your surveyor?
- Where is the cap missing, and is the insulation proud of the eaves?
- Did you see the quilt dry, and does that close the cap?
- Which rain path is left open that the quilt does not cover?
What are the typical next steps?
- Describe the missing cap as a rain path at the eaves.
- Do not treat a dry loft quilt as proof that path is closed.
- Keep this detail off the wall-tie line unless ties were separately seen.
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
If the quilt is dry, has rain been kept out?
Not proved. A dry quilt does not close a missing cap. The open eaves still leave a path for rain into the cavity.
Is a missing cap the same fault as corroded ties?
No. The cap is a rain path at the eaves. It has not measured the ties and should not be written up as tie failure.