Worried about the cracks in your walls?
Our RICS chartered building surveyors identify the root cause and tell you exactly how to fix it. Not every crack is serious, and we will tell you straight which ones are.
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How to Tell If Your Property Cracks Are Serious.
Cracks appear in almost every building at some point, and the vast majority are harmless. A few, though, are the first visible sign of structural movement that needs attention. The trouble is that a cosmetic hairline and a serious crack can look alarmingly similar to an untrained eye.
This guide explains what causes property cracks and movement in a property, which signs are worth acting on, and how a defect survey from our chartered building surveyors gives you a definite answer rather than a worried guess.
Not every crack means trouble
Buildings move. New plaster dries and shrinks, materials expand and contract with the seasons, and a recently built structure beds into the ground. All of this produces fine cracking that is purely cosmetic. As a rough guide, hairline cracks under about a millimetre in plaster are rarely anything to worry about.
The useful question is never simply “is there a crack.” It is why it is there, how wide it is, what shape it is, and whether it is getting worse. Those four answers separate the cosmetic from the structural.
Common causes of cracks and movement
Subsidence
Downward movement of the ground supporting the foundations. Across much of Kent and the wider South East it is driven by clay soils shrinking in dry spells, often made worse by nearby trees drawing moisture from the soil, or by a leaking drain washing fine material away from under the foundation. Subsidence typically produces diagonal cracks that are wider at the top and often appear around doors and windows.
Heave
The opposite of subsidence. The ground swells and lifts the structure, commonly after a large tree has been removed and the clay soil slowly rehydrates and expands. Heave can take years to play out and tends to push cracks open from the bottom.
Settlement
A newer building bedding into the ground, or made-up ground compressing under load. Settlement usually happens early in a building’s life and then stabilises, which is what distinguishes it from ongoing subsidence.
Lintel failure
The beam carrying the load above a door or window losing strength, often through corrosion or poor original specification. It shows as a crack stepping out from the top corner of the opening, sometimes with the brickwork above sagging slightly.
Wall tie failure
In cavity walls, the metal ties linking the two leaves can corrode and expand, slowly lifting the brick courses. The tell-tale sign is horizontal cracking at regular intervals up the wall, following the line of the ties.
Thermal and moisture movement
Everyday expansion and contraction as temperature and humidity change through the year. This is the most common cause of all and is almost always cosmetic, showing as fine hairline cracks that open and close with the seasons.
Warning signs worth acting on
One of these on its own is not a diagnosis, but the more of them you can see, the more sense it makes to get the property looked at:
- Cracks wider than about 5mm, or wide enough to slot a coin into.
- Diagonal or stepped cracks running through the brickwork, especially around doors and windows.
- A crack that is noticeably wider at one end than the other.
- Doors and windows that have started to stick or no longer close squarely.
- Property Cracks that are clearly getting longer or wider over weeks and months.
- The same crack appearing on both the inside and the outside of a wall.
Surveyors classify crack severity against a recognised scale (BRE Digest 251 runs from category 0 to category 5). Establishing where a crack sits on that scale is one of the first things a defect survey does.
What a defect survey for cracks includes
The aim is to identify the cause, not just describe the symptom. When you instruct Price Lilford, you get:
- A detailed on-site inspection of the affected areas, inside and out.
- The likely cause of the movement, identified rather than guessed.
- Crack measurement and classification, with a clear severity and risk level.
- Moisture readings and technical checks where they are relevant.
- Photographs of the affected areas.
- Recommended remedial options, in plain English.
- Guidance on who can carry out the work.
No jargon. No upselling. No confusion. We are RICS-registered chartered surveyors and completely independent. We do not carry out the repairs or work with contractors, so the advice you get is based on what your property actually needs.
Why early investigation matters
Genuine structural movement rarely settles on its own, and many issues worsen over time. Catching it early helps you:
- Avoid escalating repair costs.
- Prevent further damage to the structure.
- Understand the risks before buying, if it is a property you are considering.
- Make confident, informed decisions about what to do next.
A clear professional report also carries far more weight than a homeowner’s description if you are selling, remortgaging or making an insurance claim.
Related problems we diagnose
Movement rarely sits in isolation, so it is worth ruling out the issues that often travel with it:
Damp & condensation – water in the ground or structure frequently sits behind movement.
External walls & masonry problems – spalling, mortar failure and render cracking can accompany or mask movement.
Roofing & chimney issues – a leaning chimney is a classic sign of movement.
Frequently asked questions
Are cracks in my walls dangerous?
Most are cosmetic and pose no risk. The ones worth investigating are those that are wide, diagonal or stepped, that affect both faces of a wall, or that are actively getting worse. A defect survey tells you which category yours falls into.
How wide does a crack need to be before I should worry?
As a rough guide, cracks wider than about 5mm are worth investigating, but width alone is not the whole story. A 2mm crack that is steadily growing can matter more than a static 6mm one. Shape, location and movement over time all count.
What is the difference between subsidence and settlement?
Settlement is the normal bedding-in of a building early in its life, and it stabilises. Subsidence is the ongoing downward movement of the ground beneath the foundations and usually needs intervention. They can look similar, which is why the cause needs to be established rather than assumed.
Do you carry out the repairs as well?
No. We are completely independent and do not carry out repairs or work with contractors. That means our advice is unbiased and focused solely on what is right for your property.
Will my insurance cover subsidence?
Many buildings insurance policies include subsidence cover, usually with a specified excess, but terms vary, so it is worth checking your own policy. An independent professional defect report supports a claim by setting out the cause and severity clearly.
Get a clear answer on your property’s cracks
Request a defect survey and we will diagnose the cause, assess the severity and set out exactly how to put it right.
No jargon. No upselling. No confusion.