What is subsidence?
Subsidence is when the foundations of a building collapse or sink – either suddenly or gradually over time. Sinking foundations put a strain on the rest of the property and cracks usually appear in the walls.
Subsidence typically occurs due to changes in the structure of the earth under a building. For example, when the soil is too dry its structure can start shrinking and cracking. This dry ground becomes unstable and can’t support the property and its foundations. In other cases the soil might have become saturated with water over a long period of time. This can cause the foundations of a building to sink.
What causes subsidence?
Subsidence is usually caused by at least one of the following factors:
- Clay soil: Clay contains a lot of water, so clay-rich soils are particularly vulnerable to structural changes if there’s a sudden dramatic change in moisture levels
- Trees: Tree roots sap moisture from the ground, which can cause dryness in the soil, and, in severe situations, structural changes that lead to subsidence
- Heat: During periods of hot or dry weather soil shrinks, while wet weather allows it to expand as it absorbs water again – this cycle normally evens out any damage. But problems can arise with extended hot periods which dry out and shrink the soil without letting it recover properly
- Escape of water: In some instances, excessive moisture can cause subsidence. If water is leaking underneath your home, for example from a broken drain or pipe, it can soften the soil – leaving it more susceptible to sinking foundations
- Solution features: A solution feature is an underground cavernous structure created by the erosion of soil beneath the ground, which can collapse and lead to subsidence in buildings above ground. These often happen in limestone or chalk-rich ground
- Mining: Underground mines, even unused or deserted ones, can sometimes collapse and cause subsidence in buildings above the ground
- Poor ground: Properties do generally ‘settle’ into the ground as a result of the weight of the building itself. However this can lead to subsidence if the ground itself is in poor condition, or if the work done by builders surrounding the property and its foundations is poor
- Decomposing organic fill: Fill dirt is used to tend to depressions or holes in the ground, but if the fill is organic it can decompose and lose structure
- Underpinning: Underpinned foundations can be found in properties that have previously experienced subsidence, which means there is a risk that it may happen again
- Old homes: Homes built in the Victorian or Edwardian eras have shallow foundations, less than the one metre minimum for UK houses today – making them more vulnerable to subsidence
What are the signs of subsidence?
There are a number of recognisable signs and symptoms of subsidence. Keep an eye out for:
- New cracks forming or existing cracks expanding
- Wallpaper rippling in patches
- Doors and windows sticking, which is caused by door and window frames warping
How do I know a crack is caused by subsidence?
If a crack is caused by subsidence, you can usually tell because:
- It’s wider than 3mm
- It appears on both inner and outer walls
- It’s narrower at the bottom
- It’s diagonal
- It’s near to a window or door
- It gets wider over time
You might notice cracks if your home is a new build property, but this is usually just ‘settlement’ - where your home is naturally settling onto its foundations. This is a normal occurrence in new properties.
How can you prevent subsidence?
Subsidence can be hard to stop if it’s already happening but taking the following steps can reduce the risk of it starting as well as the damage it might cause:
- Regularly prune trees and shrubs close to the property to control growth and prevent excess moisture being taken from the ground by their roots
- Ensure any new trees or shrubbery are planted further than five or 10 metres away from the property
- Maintain your pipes, plumbing and drainage to prevent water leakage
- Check if there is a history of subsidence on a property before purchasing
What is subsidence home insurance?
Most standard buildings insurance policies include cover for damage to your home due to subsidence as long as your home has not had subsidence before. This means you would be covered for the cost of repairs which can be expensive.
However, there will usually be a high excess to pay – this is the first part of the claim which you must pay before the insurer picks up the rest of the bill. Subsidence claims usually have a higher excess than other common home insurance claims, such as for burglary or accidental damage, for example. This is because subsidence claims can run into hundreds and even thousands of pounds and so the higher excess acts as a safeguard for the insurer.
Some policies will cover you for alternative accommodation if you need to move out of your home while it is repaired or underpinned.
How is subsidence fixed?
The most common way to fix a home with subsidence is by underpinning the property. Underpinning is the process of strengthening the foundations of a building, sometimes by extending them, adding in support beams, or reinforcing the ground with other materials, such as concrete or resin.
Underpinning and the associated repair costs after subsidence can be expensive. Typical costs are between £10,000 and £15,000, but in some cases it can be much more.
Why are excess fees so high on subsidence claims?
Excess fees are the first portion of an insurance claim which you the customer must pay – this acts as a safeguard for the insurer to make sure you only claim when you really need to.
These fees can be higher for subsidence claims compared to ordinary home claims as the repair costs associated with subsidence can often reach tens of thousands of pounds.
Typical excess payments on a subsidence claim might be £1,000, for example, although for some insurers it may be even higher. Always check the terms of your policy.
What should I do if I have subsidence?
It’s important to contact your home insurance provider as soon as possible if you suspect your house is subsiding. They’ll organise a survey to investigate whether subsidence has become an issue, and if it is you can start thinking about the next steps to take.
When buying a new home always check for signs and symptoms of subsidence and get a full structural survey if you have concerns. Home insurance will be very expensive for a property at high risk of subsidence.
Are there any problems related to subsidence I can claim for?
Aside from subsidence, your home insurance policy may also offer cover for:
- Heave: Heave is when the ground around and under your property becomes saturated with water, causing it to swell up and push against the structure of your home. This usually has the effect of pushing up the foundations of a property
- Landslip: Landslip is when the ground around and under your home slides down a slope
Will my home insurance premiums go up after subsidence?
It is likely your home insurance premiums will go up after you have made a claim due to subsidence, heave or landslip.
Premiums cost on average £241 per year for properties that have had previous problems with subsidence - £131 per year more than properties that have had no issues, according to MoneySuperMarket data.
Based on MoneySuperMarket data collected between January and September 2020 and accurate as of November 2020.
Compare subsidence home insurance quotes
If your home is at risk of subsidence, compare home insurance with MoneySuperMarket and find cheaper cover for your property. All you need to do is tell us a little about yourself and your home, including when it was built, whether it’s already at risk of subsidence, and how much cover you’d like on your policy.
We’ll use this to put together a list of quotes from a range of providers, so you can compare deals by the monthly and annual cost of the policy, the level of cover you’ll get, and the excess you’ll need to pay to make a claim. Once you’ve found the deal you want, just click through to the provider to finalise your purchase.
As with all insurance policies, the cheapest available deal isn’t always the best. We recommend you aim to balance the cost with the cover you get, so you don’t end up under-insured or overpaying for a policy you don’t need.