Subsidence: insurance, causes and cures

Subsidence has the potential to cause all kinds of damage to your property. Here’s how you stop it

If your home suffers from subsidence, you could find yourself facing a costly repair bill or having to claim on your home insurance policy.

But with a little preparation and knowledge, you might be able to stop the problem before it starts. 

  

What is subsidence?

Subsidence is when the ground beneath your house starts to sink. This causes parts of your house to sink, too, creating misaligned walls, cracks, and damage to the building.

 

What causes subsidence?

The two main causes of subsidence are either too much or too little moisture in the soil beneath your home’s foundations. This happens when:

Nearby trees and shrubs suck up the moisture in the soil beneath your home

Leaking drains and burst pipes soften the ground beneath your house

Your house is built over an old mine or near an old quarry, which could be structurally unsound.

Periods of intense weather e.g., flooding and drought, which saturate or dry out the soil.

Clay soil is particularly vulnerable to subsidence, as it’s sensitive to moisture. This makes it expand when wet and contract when dry – not ideal with unpredictable British weather.

 

How does subsidence happen?

Subsidence is more common in Victorian and Edwardian houses as their foundations are shallower than the UK minimum (1 metre). As such, they’re more at risk of damage.

It's normally the result of a three-step process:

1. Trees and shrubbery around your home suck up moisture from clay-rich soil.

2. A 'shrink-swell' effect causes the clay to harden and crack as it dries.

3. Cracked soil causes sinking in the foundation of your home.

Subsidence is also more common in areas with clay-rich soil, like much of south-east Britain. The Subsidence Support website has a useful map of areas at risk of subsidence.

 

What does subsidence insurance cover?

Most home insurance policies should have some cover for subsidence baked into the policy. There could be exclusions, though, if your property has already fallen victim to subsidence in the past.

Policies with subsidence insurance might cover:

• Repairs to damage caused by subsidence

• Alternative accommodation if the danger or repair work is substantial

As with any home insurance claim, you’d likely have an excess to pay before you’d get any payout.

Although insurance companies offer cover for subsidence-related damage, the scale of the repairs can often leave you facing an excess of up to £1,000.

How to check for signs of subsidence

One of the tell-tale signs of subsidence is cracks along your walls.

But don’t assume that a single crack is caused by subsidence - there are a few reasons why this could be happening:

• Natural swelling/shrinking of your home’s walls in response to temperature.

• The house settling into its foundations and naturally sinking down a little - this is more common in new builds under 10 years old.

Settlement cracks generally don’t get wider with time, nor are they bigger on one side than the other. Most buildings insurance policies don’t usually cover house settlement.

Your home might be suffering from subsidence if you spot:

• Sudden cracks in plaster and brickwork that are wider at the top than the bottom

• Cracks that are visible on the outside and inside of your home

• Doors and windows sticking for no apparent reason

• Rippling wallpaper that isn’t caused by damp or moisture

• Cracks around a particular weak point e.g., where an extension meets the main property.

If you spot any of these problems it’s worth getting in touch with your home insurance company. You could also have a qualified surveyor look at the problem to limit the damage.

 

How can you prevent subsidence in your home?

There are a few steps you can take to minimise the risk of damage caused by subsidence.

 

Plant trees away from your home

According to the Royal Horticultural Society (RHS), tree roots can extend up to three times the height of the tree.

So, even if you think your trees are far enough away, they could still pose a risk. This is particularly true if you live in an area with clay-rich soil.

The Association for British Insurers (ABI), gives this guidance on how far from your home to plant certain kinds of tree:

 

So, you’re looking at a minimum distance of five metres to plant your tree, but the further away you go, the lower the risk.

 

Clean your gutters and drains

Regular maintenance on your home is generally a good idea, especially as you go into the colder, wetter months.

But it becomes especially important if your home is at risk of subsidence.

Make sure your gutters are free from debris so water doesn’t overflow into the soil. It’s also your responsibility to make sure that your drains are in good shape.

If you’re worried about drainage being a problem, you could get a CCTV drainage survey to make sure your waterworks are in good condition.

If your drains are watertight, there should also be less risk of tree roots getting in and causing further damage.

 

Check surveyor’s reports

Before you buy a house, you’ve got the option of having a building survey done of the property.

This report should tell you if there are any red flags for subsidence. You can then make an informed decision as to whether you want to buy a house that has this risk.

 

How can you fix subsidence?

The potential fixes for subsidence depend on what the cause was.

If moisture-sucking trees are the culprit, you could have them removed. Then you’d monitor the property to see if taking the trees out has stabilised the soil enough to fix the issue.

If your drains are to blame, then fixing any broken pipework could be enough to sort out the problem without a ton of cost. Again, you’d need to monitor the property to make sure the subsidence stops and doesn’t get worse.

The most common ‘big fix’ for subsidence is underpinning your foundations.

This involves installing support beams, or a second concrete layer, to strengthen your foundations.

Having an underpinned home might be an indicator to insurers that your home is at risk of subsidence again, which may lead to higher prices.

That's why it's a good idea to compare buildings insurance quotes to find the best deals.

 

What is heave?

Heave is a separate problem which is often covered under the same insurance guidelines as subsidence.

Heave has the opposite effect to subsidence. It happens when the ground beneath a building becomes saturated with water and begins to swell, moving upwards and often sideways.

This can have similar symptoms, and cause similar damage to subsidence.

Sometimes, if you take out a tree to lessen the risks of subsidence, you could then experience heave.

This is because the previously dry soil suddenly has no tree roots to absorb it, causing waterlogged soil that swells and pushes the foundations.