Wall ties and cavity insulation

What should you ask if cracks inside line up with regular brick courses?

Ask whether that pattern is on the inner leaf and whether it matches anything outside. Tie corrosion cracks the mortar courses that hold the ties, sometimes seen inside as well as out. A single diagonal crack over a door is a different pattern. The survey still has not seen the tie.

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?

Inside, people paper over the courses, so the crack may show in the lining rather than in brick. Outside, the same levels may show in the mortar. When both faces match, a tie inspection becomes a sensible question. When only the plaster is cracked at random, think shrinkage or a local knock before you think of ties. The surveyor should describe the regularity rather than jump to a product.

A borescope inspection is the usual way to see ties. It is not included in a Level 2 unless agreed. The Energy Saving Trust’s notes on cavity walls are about insulation suitability, not a method for counting ties. If the pattern is there, ask for an inspection with a number of openings. Do not price “all the ties” from a hallway crack.

What should you ask your surveyor?

Do the internal cracks line up with external bed joints?
Are they horizontal and regular, or diagonal?
Did plasterboard stop you seeing the inner leaf?

What are the typical next steps?

Photograph inside and outside at the same heights.
Do not hack off plaster before a tie firm has said where they need to look.
If you commission an inspection, ask for it in writing with the elevations covered.

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 dot-and-dab plasterboard hide this completely?

It can hide the masonry. Cracks may then show only at board joints. Say that limit out loud before you clear the wall of ties.

Is a regular crack always ties?

It is a reason to suspect them in a cavity wall. Shrinkage in blockwork can also follow courses. Seeing the tie is what separates them.