What are cavity wall ties, and what if a survey flags them?

What are cavity wall ties?

A cavity wall is two leaves of masonry with a gap. The leaves are tied so the outer skin does not act as a tall, thin wall on its own. The ties are small metal pieces bedded in the mortar. In sound walls you never see them. They become a survey item when the outer leaf cracks or bows in a way that fits tie failure, or when the surveyor knows the age and exposure of the wall make corrosion plausible and can already see a pattern.

Older cavities were often built with galvanised steel ties. Those can rust, expand, and jack the mortar bed apart, which is why the classic clue is horizontal cracking at fairly regular vertical spacing, sometimes with a bulge, often worse on a weather-exposed elevation. Later ties are stainless. We are not putting a year on your house from this page. The survey, or the specialist, has to say how this wall was built. A date guessed from a national “pre-something” rule is how sound walls get condemned.

What can a RICS survey responsibly say?

It can describe cracks, measure them approximately, note whether they repeat up the wall, and say whether the leaf is bulging. It can recommend a specialist inspection before you exchange. That recommendation belongs with a rating that matches the urgency. Widespread cracking and a bowing leaf is a serious defect in the ordinary meaning of RICS rating 3: investigate urgently, because delay can mean further damage. A single hairline bed-joint crack on a wall that is otherwise flat may only be a note. The paragraph is the difference.

It cannot say “40 percent of the ties have gone”. Nobody counted them. Level 1 will not generally tell you how to manage the defect even if it flags it. Level 3 should explain consequences. Neither level is the replacement contract. If the report says “possible wall-tie failure”, keep the word possible until someone has looked inside the cavity.

What does a specialist wall-tie inspection do?

A proper inspection locates ties, looks at their condition in sample openings or with a borescope, and reports whether replacement or isolation of the old ties is needed. It is a different visit from a general survey and a different visit from a contractor who only prices replacement. Ask for a written finding that says the ties are sound, corroded, or absent, and on which elevations. Then, if work is needed, get a separate price for that specification.

Replacement involves new ties and, where the old ones are bursting the joints, dealing with those joints. It is structural work. Approved Document A is the government’s structure guidance for England. Whether your repair must be notified to building control depends on the work. The specialist or their designer should say so in writing. Do not drill a grid of holes because a rating mentioned ties and a Saturday was free.

Should you renegotiate, repair, or walk away?

First confirm. A price cut for “possible ties” with no inspection is a guess, and the seller is entitled to say so. A confirmed failure, with a specification and two prices, is a normal rating 3 negotiation: reduce the price or agree the work before completion. Walking away fits when the outer leaf is already dangerous, the seller will not allow inspection, or the cost of repair plus whatever else the report found is more house than you want. Staying, with the work priced and a lender who is content, is also normal. Plenty of cavity walls are re-tied every year without the sale collapsing.

Do not confuse this with subsidence. Tie failure cracks beds horizontally and can bulge the leaf. Subsidence, as the ABI describes it, is the ground dropping under the foundations and more often cracks diagonally through the wall. A house can have both. The investigations are different. Send the right person.

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