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Guide to Subsidence

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Guide to Subsidence

Guide to Subsidence


Overview of subsidence

Subsidence is when a property sinks into the ground due to the contraction of the soil below it. The changes in the soil affect the foundation of the property, causing it to sink.

It is often a greater problem in clay soil because it is more prone to shrinking. In fact, the vast majority of cases occur in properties that are built on clay soil. However, soil with a large sand, chalk or gravel content can also be more affected by subsidence.

Changes in the soil are often related to the amount of water present in the soil. Subsidence occurs when there is not enough moisture in the soil, which causes it to contract. Normally, soil will expand in the wetter winter months and contract during the drier summer months, and this permanent shift keeps the foundations of the building steady. Particularly long spells of dry weather can often cause a spike in subsidence cases due to the greater degree of contraction in the soil.

Where are properties affected?

Subsidence can occur anywhere. However, in the United Kingdom, London and the South East are the areas that are most affected because of the larger amount of clay present in the soil in this region. However, subsidence can still affect properties in other areas of the country because it is not always caused by soil with a high clay content.

You can find a good overview of soil types in Britain subsidence at the British Geological Survey.

What causes subsidence?

Although contraction of the soil below a property is the cause of subsidence, there are many reasons why one property may be affected more than another even if they are built on similar soil.

Trees near your property

One of the most common causes of subsidence is the amount and type of trees surrounding your property.

Trees and shrubs suck up large amounts of moisture from the ground. They send their roots out in search of moisture, and these can stretch for many metres underneath the ground. As they suck up the moisture, the soil becomes drier and the risk of subsidence increases. This is even more problematic during prolonged dry spells.

Some trees are particularly problematic when it comes to draining the soil of moisture. These include, but are not limited to, oak, willow, ash, poplar and sycamore.

Because trees often play a role in causing subsidence, you may be asked about the number and types of trees in the vicinity of your property when you enquire about subsidence insurance.

Water leaks

Although subsidence is often caused by soil drying out and contracting, it can also be caused by an excess of water caused by a leaking pipe. If a pipe bursts under the ground, the water can wash away the particles of soil, leading to a reduction in the amount of soil. If the foundations are affected sufficiently, the property can start to sink.

Mining activity

If there has been mining activity in the area, perhaps even a very long time ago, this can also affect the foundations of your property. A collapsed mine can cause the soil to become unsettled, which can lead to subsidence in some cases. This is often more common with old, disused mines.

What about natural settling?

Sometimes a new property will settle into the soil over the first few years as the soil below it compacts. This is completely normal and is not classified as subsidence because it does not usually cause any serious problems. However, this initial settling can become a lot more significant if the ground on which the property is built is of a poor quality.

What are heave and landslip?

Heave is the opposite of subsidence, and it is not as common. It is when the ground below the property becomes saturated with water, which causes the soil to swell and expand. Instead of causing the property so sink into the soil, this has the opposite effect, pushing the property upwards.

Although it is not as common as subsidence, it can still lead to serious damage. There are certain things you can do to avoid heave, one of the most important of which is to avoid removing large trees that have been in the ground for a long time.

If you suddenly remove trees from your land, the soil can rapidly become a lot more saturated because the trees no longer soak up the water.

Landslip is when the ground physically slides. This is not as common as subsidence and is often less of a concern for homeowners.

Spotting the signs

When subsidence occurs, it can be very expensive to fix. Although many homeowners will have cover for subsidence on their insurance policies – though note that with some buildings insurance providers, subsidence is NOT included as standard – it is still crucial to spot the warning signs as early as possible. Catching subsidence early can reduce the damage and therefore the amount of money spent on fixing it, as well as the disruption caused to you and the other inhabitants.

So which signs should you be looking out for? Firstly check our short article here.

Cracks in the walls

Cracks in the walls are the most common signs of subsidence. However, just because you spot cracks, it does not mean you definitely have a subsidence problem.

Cracks can occur on the exterior and interior of your property when they are caused by subsidence. They are usually quite distinctive, tending to be narrower at one end than at the other. They usually range from about 1 mm in width to 3 mm, and often stretch out in a diagonal line.

Subsidence cracks can also appear quite suddenly, especially around doors and windows in your home. They may be deep as well, going below the level of the damp proof course. If the cracks appear after a long spell of dry weather, this could also indicate that subsidence is to blame.

If the cracks appear suddenly and then become worse quickly, sometimes over the course of a few weeks or months, there is also a chance that they are caused by subsidence.

Not all cracks are due to subsidence

Although cracks in the property are the main sign of subsidence, not all cracks indicate that you have a problem.

New buildings often suffer from small cracks as they are settling, and this is not usually anything to worry about. Buildings can also swell and shrink due to changes in temperature and humidity, and this can cause hairline cracks.

Although not all cracks are serious, you should always get them checked over by a professional as soon as possible. An expert eye will quickly be able to tell whether they are anything to worry about or not.

Doors and windows sticking for no reason

Another common sign that your property has a subsidence problem is when the doors and windows start to stick for no apparent reason. If this is due to subsidence, the doors and windows may stick because the property is shifting.

However, doors and windows can stick for other reasons. For example, a door can swell due to changes in the season, and this is nothing to worry about.

Once again, if in doubt, make sure you get your property checked over by a specialist.

Rippling in the paint or wallpaper

Rippling in the paint or wallpaper can often be a common sign of damp. However, if you do not have a damp problem in your home, you may find that subsidence is to blame.

What to do when you spot potential signs of subsidence

As soon as you spot any of these telltale signs of subsidence, it is better to be safe than sorry. If you have buildings insurance with cover for subsidence, contact your insurer immediately. They will want to know as soon as possible so that, if necessary, they can act to prevent more serious damage occurring.

Your insurer will probably send an expert to check over your problem and identify whether subsidence is to blame or not. If it is to blame, they will then discuss options for fixing it.

How to reduce the risk of subsidence

Prevention is better than cure with most things in life, and the same can certainly be said for subsidence. If your property is affected by subsidence, not only can it be very costly to fix, but it can also cause a great deal of disturbance for you and the other inhabitants.

Even if you have subsidence insurance, you may be required to pay a large excess – with most policies the amount is £1,000, however it can typically be up to £5,000 – for any repairs, so it makes good sense to reduce the risk as much as you can.

Control trees and shrubs

One of the most important ways to reduce the risk of subsidence is to carefully control any trees and shrubs that you have in your garden. This can include:

  • Avoid planting new trees too near to your home. Not only can the roots cause physical damage as they grow, but they can drain the water from a large area. If you do want to plant trees, make sure you plant them far enough away from your property that they will not be a problem. As a general rule, plant them the same distance as their expected maximum height;
  • You should also consider neighbours’ properties before planting any trees because you do not want to cause them any subsidence problems either;
  • If you already have trees near to your property, you may want to consider removing them completely. However, this is not always a good idea. As mentioned earlier, removing the trees can lead to an increase in the amount of water in the soil, which can cause heave;
  • Find out whether the trees were planted before or after the property was built. If they have been in the ground longer than the property, it may be best to leave them where they are. If they are newer, however, you may want to remove them;
  • Rather than removing the trees completely, you may want to consider cutting them back and thinning them out instead;
  • The types of trees can also be an important consideration when you are planting new trees. Broad leaf trees tend to cause more risk of subsidence because they require more moisture, whereas evergreens do not cause as many issues;
  • Rose shrubs, pyracantha shrubs and wisteria are also potentially problematic because of the amount of moisture they absorb, so avoid planting these too near to your property. If you do want them near to your property, you may want to plant them in containers instead.

This can be a specialist area, so you may want to discuss your plans with an experienced tree surgeon and ask for their recommendations before doing anything. You can find information here about what to do if you suspect a tree is causing problems.

Inspect drains on a regular basis

Leaking drains and pipes under the ground can cause subsidence, so you may want to arrange for inspections on a regular basis. This might be more of a concern if you live in an area more prone to subsidence, but it is a sensible step to take whatever the soil conditions.

It may be worth carrying out an inspection before you buy a property to make sure there is nothing to worry about before you part with your money – especially if you are buying at auction where you are buying the property “as seen” and are therefore not entitled to get your deposit back if you change your mind / discover a problem.

Conduct careful research before buying a property

Before you buy a property, you may want to find out whether there has been any mining activity in the area, perhaps decades earlier. Carry out careful research beforehand because it could reveal potential problems.

Ensure renovations are constructed properly

If you plan a renovation, such as adding on an extension to your property, make sure it is carried out by professional and experienced builders. If the wrong foundations are used, the soil may settle badly and the extension may sink lower than the level of your home.

Getting insured

Even if you have never suffered from subsidence, or you live in an area where the risk is considered small, you should not let yourself fall into a false sense of security. Subsidence can happen to any property, and the repair costs can be very large.

If you do not want to take any risks, you may want to find out about getting your property insured.

Not all insurance companies cover subsidence

The first thing that you should know about subsidence insurance is that not all buildings insurance companies provide cover for it.

A company may provide adequate cover for other situations, but it may simply not provide cover for the costs of fixing subsidence issues. However, some insurers, like all of ours at GSI Insurance, do cover subsidence as standard.

This is something you may want to look out for when choosing a policy because it can make a big difference in your decision making

Excess issues

Excess is the amount of money that you will have to pay when making a claim. For example, if you make a successful claim for £500, you may have to pay the first £50, and this is standard on just about all insurance policies.

When it comes to protection for subsidence, you may have to pay a high excess, sometimes of £1,000 or even £5,000, and the exact amount will depend upon the insurer. This is because subsidence is often very expensive to fix.

Insurance typically only covers the main building

Subsidence can affect the main property as well as walls, gates, sheds and other structures. However, typically insurance only provides repair costs for the main building itself, so this is something to keep in mind.

Alternative accommodation costs

If your property requires extensive repairs, you may find that you / your tenants are unable to live in the property for a period of time. Some insurance policies may include expenses for alternative accommodation, which can take a weight off your mind, so this may be something you want to consider.

Getting insurance after you have suffered from subsidence

If your property has already experienced issues with subsidence in the past, you may find that it can be more complicated when you want to take out an insurance policy. This is because it represents a larger risk for the insurer.

Some insurers may refuse to cover you for subsidence completely, while others may do, but could set a higher excess, such as £5,000, or load up your premiums. The provider may also have different terms and conditions, so this is something you should be aware of.

At GSI Insurance we have specialist insurers who understand subsidence and its repair. These are insurers are typically able to find your affordable buildings insurance cover, including subsidence.

Discovering subsidence after changing insurers

If you decide to change your insurance provider and then find subsidence at a later date, you may find that your previous insurer is actually responsible for making the changes.

This will typically be the case if the subsidence is discovered within eight weeks after you change companies. If subsidence is discovered after eight weeks but before one year after changing insurers, the two companies may share the costs. Once a year has passed, the new insurer is usually responsible.

Always contact your insurer when you suspect a problem

When you notice the signs of subsidence, always contact your insurer immediately. Even if it turns out to be nothing, they will want to know so that they can send a structural engineer to check it out and monitor the situation so that they can make any repairs if necessary as soon as possible.

Take subsidence seriously

Subsidence can be very distressing for homeowners. You can never be 100% sure that you will not face problems with subsidence, so it is important to take all the necessary precautions, including following prevention tips and taking out insurance.

Do not leave yourself at risk of paying large costs for subsidence. Find out the risks in your area, take sensible precautions, look out for the potential problem signs and consider taking out an insurance policy that covers your property should it be affected by subsidence.

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