Subsidence: why it happens and how to deal with the damage
 
Could your home be at risk of subsidence? We explain how subsidence happens, show you how to spot the signs early and how you can fix any damage caused.
 
Time and changes in temperature and humidity can cause your home to move and settle, resulting in hairline fissures and minor surface cracks to your property. These will not cause any lasting damage and are usually nothing to worry about.
 
Subsidence, however, is the result of sinking ground beneath your home and damage to the deeper structure. Read on to find out about subsidence and how you can deal with the damage it can cause.
 
How it happens

Subsidence occurs when the ground beneath your home starts to sink, causing the property to move on its foundations or a failure of the foundations themselves. This can happen for a number of reasons, including:
 

• Dry weather

Subsidence can occur during long periods of unusually dry weather, when the soil contracts too much, it can’t support the building properly.
 

• Soil type

Some types of clay soil can be particularly affected by long dry periods. The clay shrinks due to dehydration and is slow to rehydrate leading to long-term subsidence of the ground above it and damage to buildings.
 

• Water damage

While too little water can damage soil, so can too much. Leaks from underground drains and pipes or overflowing gutters around the property can wash away soil or make it saturated, again meaning that the ground may not support the building properly.

 

• Vegetation

Trees are a big problem when it comes to subsidence. Large trees will extend their roots over great distances and suck the ground dry of moisture over long periods of dry weather. The main culprits are ash, oak, plane, poplar, sycamore and willow.
 

• Location

It is rare, but if your home is built on or near an old mining site there is a chance that the ground could be structurally unsound.
 
How to spot it

Cracks caused by subsidence are easy to spot. Here’s what to look out for:
 

• Shape

Subsidence cracks tend to be diagonal, narrower at one end and usually increase in width over time.
 

• Location

Look for cracks that are visible both inside and outside the property, and that appear around doors and windows. They also tend to extend below the damp-proof course.
 

• Timing

Subsidence cracks will often appear after long periods of dry weather.
 

• Other signs

Windows and doors can start sticking as the property shifts out of alignment and, with extreme subsidence, floors become uneven.
 
How to prevent it

You can reduce the risk of subsidence in a number of ways:
 

• Plant trees and shrubs in your garden as far as possible from your home. You may be able to prune or remove trees that could be a problem, but check with a professional first – some older trees may carry preservation orders and permission will be needed from the local authority to remove or reduce them.
• Check pipes, gutters and drains frequently to make sure there are no leaks that could be adding excess water to the soil.

 
Can it be fixed?

As soon as you see any tell-tale signs of subsidence, you should contact your insurer so that they can send round a specialist to assess the problem. It may take some time to establish whether the problem is subsidence or not, so regular monitoring may be necessary. Most subsidence can be fixed; the key is spotting it early.
 
If your property is being damaged by subsidence, it can be fixed by a few methods, including:
 

• Tree removal

Usually, pruning or removing nearby trees will stabilise ground movement.
 

• Underpinning

It’s rare that a property will require underpinning, but if it does you may be required to move out of your home while repairs are carried out. If underpinning is needed, many modern repair methods are relatively unobtrusive and can be completed with minimal disturbance
 
Most building insurance policies cover damage caused by subsidence, but you will need to check this, and be aware that you will usually need to pay a subsidence excess, which is more than the standard.
 
UIA Mutual Insurance is the trusted insurance provider for Usdaw. Their buildings insurance policies cover you for subsidence and heave, including necessary monitoring and repairs, and the cost of any alternative accommodation should your home become uninhabitable. Find out more on the UIA Mutual website.