What is subsidence and how can it affect your home insurance?

Subsidence insurance

If you’ve found your dream home but the survey suggests it might be subsidence-prone, or you’ve noticed changes in your own home and wonder if you should be concerned, put your mind at ease by reading through the following information on what subsidence is, what you can do about it, and whether you’re covered by your home insurance.

What is subsidence?

Subsidence is when ground underneath a building sinks and pulls the building’s foundations down with it. You might find evidence of subsidence when the ground loses moisture and shrinks due to long periods without rain, or when trees and shrubs are planted too close to the building causing the soil to dry out.

What causes subsidence?

Subsidence happens for a number of reasons including:

• Type of soil – the water content of different soils has an impact on their chances of causing house subsidence, with heavy clay soils being especially prone to cracking and shrinking in hot dry weather.
• Leaking drains and water mains – leaking pipes or drains can wash away soil or cause it to soften. Too much water in sandy and gravelly soils increases the chances of the ground washing away.
• Trees and shrubs – if these are planted too close to the house and become too large, they can dry out clay soils as they take up water to grow.
• Mining activity – if houses are built on or near filled-in quarries or mines, the ground can become unstable if the material used to fill them in collapses creating sinkholes. Digging out basements can also affect foundations.
• Solution – a natural underground cavern usually in limestone or chalk caused by rising of the water table, which can become unstable like a mining tunnel.
• Poor ground preparation – this is due to the quality of the fill materials used in the foundations themselves, a lack of compaction or decomposing organic fill.

Building foundations might also be affected by other issues such as heave, when the ground underneath moves upwards due to over-saturation, and landslide, when a building moves down a slope with the ground underneath.

How to check for subsidence

The first signs of subsidence in a house are usually cracks appearing in external or internal walls.

But not all cracks mean you have subsidence. New homes may have cracks as they settle, or houses can display fine cracks with temperature and humidity changes.

Subsidence cracks look quite different to other cracks. Internal subsidence cracks usually appear suddenly and can be found mostly around doors and windows.

Common early signs of subsidence include:

• Diagonal cracks in the walls, visible internally and externally, which are usually wider at the top than the bottom
• Cracks that are thicker than a 10p coin
• Doors and windows sticking or not shutting properly
• Wallpaper crinkling or ripping when not caused by damp.

How to prevent subsidence

Natural ground subsidence is when the ground cannot support the weight of the building due to natural causes like trees or a spell of dry weather. There are some steps you can take to reduce the risks:

• Remove trees and bushes that are planted near the house. Trees are a common cause of subsidence as their need for water can make surrounding soil too dry to support foundations
• If you can’t remove the trees, keep them trimmed to a manageable size to limit their water uptake
• Inspect your gutters and drainage systems regularly so you can spot any leaks or blockages before they become a problem.

How to fix subsidence

If you do spot signs of subsidence in and around your home, you’ll want to look at subsidence repair pretty quickly, before any issues get worse. If you have a policy that covers subsidence, you should contact your insurer for help as soon as possible.

Your insurer will advise you on the next steps and will usually send a specialist like a structural engineer or surveyor to examine the damage and confirm whether subsidence is the cause.

• If there’s only a small amount of damage and the cause is obvious, repairs can be made straightaway.
• If the damage is severe and it still seems to be happening, your house might need to be monitored over time to work out the cause and the right long-term solution.
• If the house subsidence is very severe, your house may need to be underpinned, with the foundations strengthened to prevent any more damage.

If it’s found that the subsidence has been caused by coal mining, you’ll need to get help directly from the Coal Authority, although you should keep your insurance provider informed of any claim.

How much does subsidence devalue a property?

Subsidence can have a significant impact on the value of your property, dependent on how severe the effects are.

Anna Thunstrom, Home Product Manager advises: "If you want to sell a property that’s been affected by subsidence, your estate agent will consider the impact when they give you a valuation, and it could affect the market value of your home by as much as 20%."

If you’re thinking about buying a house with minor subsidence you should make sure that any potential issues are considered when you make an offer. You should also talk to your insurance provider to see if you’ll be able to get suitable cover for a property that has a history of subsidence.

Anna adds: "Older homes, particularly those with unique or historical features, might be more expensive to repair or rebuild, and they could be at greater risk of issues like subsidence. This could lead to higher premiums."