After a hot, dry summer, many homeowners start noticing cracks they had not seen before. A diagonal crack beside a window. A stepped crack through brickwork. A gap that looks wider than it did a few months ago. It is completely understandable that the first thought is the dreaded S word: subsidence.
But the first step is not to panic, and it is not to rush straight into filling cracks, removing trees or commissioning repairs. The first step is to understand what you are looking at, what it might mean, and what your insurance position is before you accidentally make things more complicated.
For the crack itself, surveyors and engineers commonly refer to BRE Digest 251, published by the Building Research Establishment. BRE Digest 251, Assessment of damage in low-rise buildings, is a recognised technical reference used to assess cracking by width and severity. It helps professionals think about whether cracking appears very slight, slight, moderate, severe or potentially more serious.
But once subsidence, heave or landslip is suspected, the issue is no longer only technical. It also becomes an insurance issue. That is where the ABI, the Association of British Insurers, becomes relevant. The ABI is not a structural authority, and it is not there to diagnose the crack. Its relevance is insurance: how buildings insurers generally approach subsidence claims, cover, excesses, renewals and future insurance implications.
That distinction matters. BRE helps you understand the crack. ABI helps you understand the insurance context.
Why cracks can appear after dry weather
Subsidence happens when the ground beneath part of a building loses support and moves downward. Heave is different. It happens when ground swells and pushes upward. In many parts of the UK, the concern after a long dry spell is shrinkable clay soil. Clay can shrink when it dries, and large trees or hedges can increase the effect by drawing moisture from the ground.
That does not mean every crack near a tree is subsidence. Buildings crack for many reasons. Thermal movement, historic settlement, plaster shrinkage, lintel movement, drainage defects, poor alterations and seasonal changes can all play a part. What matters is the pattern.
Cracks that are wider than hairline, diagonal, stepped through brickwork, visible both inside and outside, or concentrated around openings deserve more attention. Cracks that suddenly appear after a dry summer, especially near large trees or drains, should be recorded properly and considered carefully.
A simple practical check is whether the edge of a pound coin fits into the crack. That is roughly 3mm, which is often a point where further assessment becomes more sensible. Width alone never tells the whole story, but it is a useful starting point.
Do not just fill the crack and hope
It is tempting to fill the crack, repaint the wall and move on. Sometimes cracking is minor and decorative repair is all that is needed. But if the cracking could indicate structural movement, simply decorating over it may create a poor paper trail and a bigger problem later.
If you later sell the property, you may be asked about movement, insurance claims, structural repairs, disputes, guarantees, investigations and anything that may affect a buyer’s decision. If you knew about a possible issue and failed to disclose it properly, you could find yourself in a legal dispute after completion.
Not claiming on insurance does not necessarily make the issue disappear. If you knew about it, investigated it, repaired it, monitored it or received professional advice about it, it may still be relevant to a future buyer.
That is why the priority is not simply “who pays for the repair?” The priority is clarity. What caused the crack? Is the movement ongoing or historic? Has it stabilised? Was drainage checked? Were trees assessed? Were repairs appropriate? Is there evidence?
A properly investigated issue with clear records is usually far easier to explain than a vague history of cracks, informal repairs and no conclusion.
If you have buildings insurance, think before going it alone
This is the part many homeowners miss. If you have buildings insurance and you suspect subsidence, heave or landslip, you need to understand your policy position before commissioning major works yourself.
Some owners worry that making a claim will affect premiums, future cover and resale value. That concern is understandable. Subsidence can carry stigma, and it can affect how buyers, lenders and insurers view a property. But avoiding a claim is not always the safer option.
A useful point made by Bob Gibson, a subsidence consultant, is that if you merely notify an insurer but do not make a formal claim, or if the insurer has not accepted the claim, you may not have the same protection as you would under a proper claim process. The insurer may be relieved that you want to deal with it yourself, but that does not necessarily mean they will maintain subsidence cover later.
So the sensible advice is not “always claim immediately” and it is not “never claim because it will blight the house.” The sensible advice is this: if subsidence is genuinely suspected, speak to your insurer or broker before taking major steps. Understand whether notification is required. Understand the excess. Understand the process. Understand what happens to future subsidence cover if you investigate or repair privately.
If you are going to involve your insurer, think carefully before trying to sit halfway between notifying them and avoiding a claim. If the issue is genuine subsidence, a formal claim may give you a clearer route, a clearer paper trail and a better future insurance position than trying to quietly manage it alone.
Why selling changes the advice
If you are not planning to sell, the focus is usually investigation, stability and repair. If you are selling, or hoping to sell soon, the advice changes slightly. You are not just trying to understand the crack for your own peace of mind. You are also creating the evidence a buyer, solicitor, lender or insurer may later rely on.
A retired property underwriter made a very useful point in the discussion that prompted this article. From an underwriting perspective, the issue is not only whether the owner makes a claim. It is whether the cracking, suspected movement, structural report or repair history is something an insurer or buyer would reasonably expect to know about.
That matters. If the property is on the market and cracks appear, simply filling them and saying nothing is risky. It may not protect the sale, and it may create a much bigger problem later if movement is identified after completion.
If the cracking is not serious, your best weapon may be the report. A good structural engineer’s report saying the cracking is minor, historic, weather-related or not structurally significant can help reassure buyers. It shows that you did not ignore the issue, hide it, or guess.
Buyers are often less worried by a clearly explained issue than by a vague one. Fresh filler and no paperwork can create more concern than a report that explains what was found and why no further action was recommended.
Can you instruct your own expert?
Yes, and in many cases that may be sensible. You do not necessarily have to sit back and wait while an insurance process moves slowly. An independent structural engineer can inspect the cracking, consider likely causes and advise what investigation is needed.
A CCTV drainage inspection may also be an important early step. Failed drains can cause or contribute to movement by softening or washing away supporting ground. Even where drains were not the original cause, movement can damage nearby drains. Many structural engineers will want drainage defects ruled in or out early because it is one of the clearest starting points.
Where trees are suspected, arboricultural input may also be needed. But there is a difference between getting proper advice and rushing into action. Removing a large tree without the right evidence can be risky. On shrinkable clay, tree removal may allow the clay to rehydrate and swell, which can create heave. Some trees may also be protected by a Tree Preservation Order, or may fall within conservation area controls.
If a neighbour’s tree is involved, the situation can become even more complicated. You may need evidence showing that the tree is implicated, not just suspicion. That evidence may include crack monitoring, soil testing, root identification, drainage results, arboricultural advice and structural engineering input.
The tree or the clay? Usually, it is the relationship between them
Homeowners often ask whether the problem is the tree or the clay. In many cases, that is the wrong way to frame it. Clay soil is the ground condition. The tree can be the trigger that changes the moisture balance. The risk comes from the relationship between shrinkable clay, foundation depth, seasonal weather, nearby vegetation and the building itself.
You cannot remove the clay. You may be able to manage the tree, install a root barrier, repair drains, improve water management, or carry out structural repairs where justified. But each option has consequences, and the wrong action can make matters worse.
That is why suspected subsidence should not be rushed. Nobody wants to watch cracks open while monitoring takes place, but monitoring exists for a reason. It helps establish whether movement is active, seasonal, progressive or historic. Without that evidence, it is easy to spend money on the wrong repair.
What you should do first
Start by recording what you can see. Photograph the cracks clearly. Take close-up photos and wider photos showing where the cracks sit on the wall, elevation or inside the room. Measure the width if possible. Note the date you first noticed them. Check whether the same crack appears inside and outside. Look for sticking doors or windows, sloping floors, gaps around skirting boards, rippled wallpaper, reopened filler or fresh cracking through previous repairs.
Then look around the property. Are there large trees nearby? Have any trees recently been removed? Are gutters leaking? Are drains blocked? Is there recent excavation, a new extension, raised ground, leaking pipework or changes to hard landscaping? These observations do not prove the cause, but they help the next professional ask better questions.
If the pattern suggests possible structural movement, speak to your buildings insurer or broker before commissioning major works. Ask what you are required to report, whether opening a claim is appropriate, what the excess is, what investigation process they would follow, and what happens to future subsidence cover if you investigate or repair privately.
Then get the right evidence. That may mean a structural engineer, CCTV drainage inspection, arboricultural advice, crack monitoring, or a combination of these. The correct route depends on the property, the cracking and the suspected cause.
The uncomfortable truth about value
Subsidence can affect value, even when repaired. Some buyers will be cautious. Some lenders may ask more questions. Some insurers may apply higher excesses or premiums. That is frustrating, especially when the movement has been properly dealt with.
But uncertainty usually causes more damage than disclosure. A buyer is more likely to be reassured by clear evidence showing what happened, what caused it, what was done and whether the property has remained stable. A property with old cracking, no records, no explanation and no insurance clarity is much harder to defend.
If concerns like these are first raised during a buyer’s survey, our guide on What Happens After a Bad House Survey? explains what can happen next and the options available to buyers and sellers.
If you are planning to sell soon, this becomes even more important. Do not assume that avoiding an insurance claim avoids the need to disclose. If you know about suspected movement, professional advice, monitoring, drainage defects, tree-related issues or structural repairs, take legal advice on what must be declared.
How Survey Shack fits in
Survey Shack does not decide insurance claims, diagnose subsidence or replace a structural engineer. But we help owners understand what they are looking at earlier, before panic takes over and before expensive mistakes are made.
Our guided condition assessment helps you record the right evidence, recognise patterns that may need escalation, and understand whether the next step is likely to be monitoring, drainage investigation, structural engineering advice, arboricultural input or insurer involvement. The aim is not to frighten people. The aim is to get them asking the right questions in the right order.
With cracks after a hot, dry summer, the worst outcome is not always the crack itself. It is delay, guesswork, undocumented repairs and poor decisions made before the insurance position is understood.
Do not panic. Do not hide it. Do not just fill it. Record it, understand it, and get the right advice before deciding what to do next.
