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Concerned cracks could be subsidence? The cause is usually less sinister
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Although some cracks are warning signs that the ground beneath a building is shifting and causing structural damage, most are harmless.
Common causes of minor cracks include:
All new buildings – or new extensions to homes – settle downwards under their own weight. This can cause cracking without any threat to the structure.
Usually, settlement cracks appear at weak points, like around windows and doors.
It can take a couple of years for a building to settle, so you can expect some minor cracks to appear in new builds for quite some time.
All buildings, new and old, expand in the heat and contract in falling temperatures. You may have even heard creaks or snapping sounds as these movements occur.
Thermal cracks caused by this sort of movement are minor and easily repaired.
In newly-built homes, moisture in building materials like wood, concrete and mortar dries out over several months. This results in some shrinkage, which can lead to cracks, usually near ceilings and floors.
In homes old and new, cracks can appear when building materials expand and shrink depending on how much moisture is in the air.
Materials expand as they absorb the water vapour that’s expelled in our homes when we take baths and showers, or boil kettles and cook, for example. Then they shrink as they dry out when it’s warm outside or when the central heating is on.
Cracks can also be caused by:
Minor cracks that measure no more than 2mm are usually nothing to worry about and will have no effect on the safety and stability of your property. You can easily check the width of cracks with a measuring tape.
But you should investigate cracks that:
These sorts of cracks could be a sign of structural damage and subsidence.
Cracks and bulges in the exterior render of a property can happen for a variety of reasons, most of which aren’t serious. For example:
Any crack in the render of your home should be attended to. Even small cracks can allow water to seep into the brickwork and cause more damage - like damp, or wider cracks if the water freezes in cold weather.
You can either cut out and fill these types of cracks or if the render is ‘blown’ and has become detached from the wall, it’ll need to be taken off and the render replaced.
Any cracks measuring more than 15mm should be investigated by a professional.
Subsidence happens when the ground beneath a property erodes and moves downwards.
As the ground sinks, it pulls the property’s foundations down with it, damaging its structure and causing cracks.
Heave, on the other hand, is when the ground moves upwards, or swells, causing a property to lift. It’s less common than subsidence.
Heave and subsidence can occur when soil gets too wet due to flooding, or too dry due to excessive periods of drought.
These type of ground movements tend to happen in:
As well as wide cracks appearing, signs of subsidence can include:
The Building Research Establishment (BRE) identified six categories of crack to help surveyors and insurance assessors identify whether a crack is likely to affect a property and the type of repairs that would be appropriate.
Broadly speaking these are:
Look out for the direction in which a crack runs through the wall as this can sometimes help determine how serious it might be and how to treat it.
In a newly-built home, you can help to keep cracks at bay by allowing building materials to dry out gradually so that shrinkage is not too sudden.
Try leaving window vents open to allow for natural evaporation of moisture and avoid cranking up the central heating too high as excessive heat can speed up the drying process and cause cracking.
If you live somewhere that’s prone to subsidence issues – such as a clay soil area – there are some things you can do to help prevent the problem.
When you next decorate, you can easily repair minor cracks using a filler, then lightly sanding before applying paint.
If a crack is wider and more severe, you should get the advice of a professional structural engineer. They can determine if they think the crack/s are an indication of structural damage and next steps to take.
If you suspect subsidence, you should contact your insurer.
They may send out a building specialist or surveyor to take a look.
The specialist might want to place monitors onto cracks to check for ongoing movement and to assess the ground below the foundations.
If movement of your home has stopped, then repairs to damage can go ahead.
If movement is ongoing and is causing major structural damage, then you may need to have your home underpinned. This involves lifting, re-levelling and strengthening the ground underneath the building.
If you’re renting, contact your landlord about any concerning cracks. And if you’re a leaseholder, contact the freeholder. It’s their responsibility to investigate the problem and to claim on their buildings insurance for repairs if necessary.
Small, hairline cracks are normal as a newly-built property or extension settles, or as any home ages and is lived in.
Minor cracking is a cosmetic problem, and any repairs needed won’t be covered by buildings insurance.
Cracks that form as the result of subsidence, though, are usually covered by a home insurance policy.
This is true only if your home has not suffered subsidence in the past (though there are some specialist insurance policies that will cover properties with subsidence history.)
Your buildings insurance policy will cover the cost of repairing damage to the structure of your home that occurs as the result of subsidence, including cracks.
It won’t normally cover the cost of preventing further subsidence and movement of your home though.
Some policies offer to cover the cost of your accommodation if your home needs extensive repair and you have to move out.
Subsidence claims usually come with an excess in the region of £1,000.
Premiums and excesses usually increase after you’ve made a subsidence claim with your insurer, especially if it’s still at risk of further movement.
Some companies won’t insure you at all if your home has had subsidence issues as they see it as too much of a risk.
You may need to shop around for specialist insurers who will cover you.
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