Wall ties and cavity insulation
Does hollow render mean the wall ties have failed?
Not by itself. Hollow render means the coat has left the wall. Ties fail in the cavity, usually with a pattern of horizontal cracks in the bed joints, which render hides. A surveyor who cannot see the brick should say the ties were not assessed. They should not declare failure, and they should not declare the ties sound.
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?
A borescope inspection needs holes. It is not part of a standard Level 2 unless you agreed it. The Energy Saving Trust’s cavity-insulation advice assumes a wall in good condition, a clear cavity of at least 50mm, and repairs done first. You cannot know that through hollow render by tapping alone.
Quote the render if it is letting water in. Quote a tie survey only if age, exposure and the parts of the wall you can see justify it. They are different invoices. No price for either is stated here. A hollow sound on one panel is a render note. It does not, by itself, mean the cavity ties have failed across the whole elevation.
What should you ask your surveyor?
- Could you see any bed-joint cracking, or only the render?
- Is this a cavity wall?
- Would you need openings before you would comment on ties?
What are the typical next steps?
- Do not hack off all the render before a specialist has said where they need to look.
- Do not buy cavity insulation while the coat is hollow.
- Read the tie pages only if the wall is actually a cavity wall of the age that used metal ties.
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
Can render fall off a solid wall?
Yes. Solid walls are rendered too. No ties are involved. Ask the surveyor which wall they mean.
Is a crack at the corner of a window a tie crack?
Often it is the opening. Tie patterns tend to run in courses. The survey should not rename one as the other without the pattern.