Subsidence: what is it, how do you spot it and what should you do if you have it?

Damage caused by subsidence can be expensive to fix. In fact, our most expensive claim for subsidence damage was £71,800! The good news is that our average claim size for subsidence is cheaper than you might think at just £11,423. 

The key thing with subsidence is to take action right away. It can be tempting to put off dealing with it, but the longer you leave it, the more expensive your repairs will probably be.

To help you make the right decisions, we’ve rounded up everything you need to know about subsidence.

There’s a lot of information here, but you can skip ahead using the menu below:

What is subsidence?

Subsidence: what is it, how do you spot it and what should you do if you have it?

Subsidence is when the ground beneath a property sinks, pulling the property’s foundations down with it.

This process can cause the walls and floors to shift, leading to cracks and potentially destabilising the construction of the property.

What causes subsidence?

Subsidence can be caused by a range of things including clay shrinkage, trees growing close to the foundations, water washing away soil beneath the property, used or disused mines, formation of underground caverns and poor foundations.

Clay shrinkage

Warmer weather is one of the most common causes of subsidence. In fact, subsidence claims increased by 20 per cent in 2018 because of the UK’s heatwave. 

As the ground below a property warms, clay-rich soil can shrink as the water trapped in it evaporates. This causes the soil to shrink, leading to the downward movement of the ground above.

Trees

Trees may look harmless enough, but they can cause subsidence in two different ways. 

Drawing water out of the soil can cause that soil to shrink – and a mature oak tree can draw up to 1,000 litres per day! Trees growing near to or under the foundations can also cause the ground to shift and become less stable.

Washing away of soil

Leaking drains, escape of water, flooding and heavy rainfall can wash away soil particles over time, causing the ground to slowly shift or become less stable.

Poor foundations

Older properties often have shallower foundations than new builds. The use of the wrong materials in the foundations or not properly preparing the earth can also lead to foundations shifting below the property in new developments as well.

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What is the difference between subsidence, settlement, heave and landslip?

Subsidence is just one of the types of ground movement beneath a property, but there are others including settlement, heave and landslip. 

What is settlement (also called compaction)?

Settlement and subsidence are often confused. It’s important to understand the difference between the two, because some insurers will cover subsidence but not settlement. 

Hamilton Fraser, for example, does not cover the normal settlement, shrinkage or bedding down of new structure or the settlement or shrinkage of made up ground or of materials brought to the site.

Subsidence: what is it, how do you spot it and what should you do if you have it?

Settlement occurs when the ground below a property is compacted by the weight of the building. This usually happens in the first 10 years after building and is relatively common. Cracks in the walls caused by settlement are usually harmless and can be plastered over. 

However, cracks that appear and continue to grow, reaching a width of 15mm or more, should be investigated to make sure that the property is structurally sound. 

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What is heave?

Heave is essentially subsidence in reverse. The ground below your foundations moves upwards, causing the foundations, walls and floors to shift.

The most common cause of heave is when the soil beneath the house becomes saturated with water that has no way to escape – often because a mature tree near the property has been removed or died. This causes the soil to expand, pushing the foundations 

upwards or sideways. 

Subsidence: what is it, how do you spot it and what should you do if you have it?

What is landslip?

Subsidence is down, heave is up – so what is landslip? 

Landslip is the sideways movement of the ground beneath a property, often the result of soil erosion or the property being built upon or near to a slope.

Subsidence: what is it, how do you spot it and what should you do if you have it?

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What are the signs of subsidence?

Since you can’t see what’s going on below ground, the evidence of subsidence is usually found in the property itself, most often as cracks in the walls.

Cracks in the walls

Don’t worry, not all cracks are signs of subsidence. Most cracks in the walls are harmless and perfectly normal. 

Cracks caused by subsidence tend to have a few noticeable characteristics. Here are a few questions that will help you tell if your cracks are caused by subsidence.

  • Is the crack wider at the top than it is at the bottom?
  • Is it wider at any point than a 10p coin (roughly 3mm)?
  • Can the crack be seen from both the inside and the outside of the property?
  • Are the cracks found close to weak spots like doors, windows or where extensions join the house?

Subsidence: what is it, how do you spot it and what should you do if you have it?

If the answer to any of these questions is yes, it may be worth getting an expert to assess whether subsidence is an issue. 

Ripples in the wallpaper

Wallpapers can start to wrinkle or crease because of condensation, but it can also happen because of subsidence. 

A good way to test whether the ripples are the result of dampness is to check the windows for signs of condensation first thing in the morning. If there’s no condensation, it might be a sign of subsidence. 

Doors and windows no longer fitting

Cracks caused by subsidence often appear near to doors and windows. If your doors and windows no longer fit or are tighter than they used to be, that may be a sign of subsidence. 

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What are the risks of ignoring subsidence?

In most cases, subsidence happens slowly. Because of this, it can be tempting to put off dealing with it or to convince yourself that there isn’t really a problem at all. Unfortunately, this can create more problems in the long run.

Loss of property value

Properties with a history of subsidence are often harder to sell, which means that you’ll have to sell at a lower price. 

It’s expected that people who are selling a property with a history of subsidence are honest with their letting agents and potential buyers. It’s likely that any buyers will ask for as much documentation and information as you can give them.

Don’t try to cover subsidence up. Most buyers will conduct a survey before handing over any money, which will reveal  the subsidence. At this point it’s likely they’ll either pull out of the deal altogether or ask for a dramatically reduced price.

Similarly, most renters won’t want to live in a property which doesn’t feel secure, which may mean that you have to put your property on the rental market at a lower price.

Serious structural damage

If subsidence isn’t addressed in the long term then there is a risk of serious structural damage and even collapse.

As is often the case, the cost of preventing this kind of damage will probably be lower than the cost of repairing it.

Higher insurance premiums

Most insurers charge higher premiums to cover properties with a history of subsidence because there’s a higher chance of damage claims.