Subsidence – What is it and how to prevent it?

 If you have trees or large shrubs planted too close to your home they can cause subsidence as the plant drains the moisture from the soil causing it to dry out and sink. Estimates suggest that around 70% of all subsidence cases are a result of tree roots absorbing all the moisture out of soil.

 This type of soil changes a great deal with the weather. When it is hot and dry it can shrink, crack and shift which makes the ground unstable and there is a greater risk of it sinking.

If you live somewhere that is prone to a drought then the soil could dry out which increases the chance of subsidence.

A leaking drain or water main can soften the soil, or wash it away, causing sinkage.

If you live in a period or historic property, there may be a greater risk of subsidence as your house may have shallower foundations than a more recently built home. However, the flipside is that older properties tend to be built from bricks and lime mortar, which could make them more flexible and less likely to be damaged by the ground shifting beneath them.

This is one of the more well-known causes of subsidence. If your house has been built near to a former quarry or pit, then it could be unstable as the material used to fill the site will shift as it decomposes.

 If the foundations aren’t done correctly before building, this can lead to subsidence problems.

In the worst cases of subsidence, your house may need to be underpinned. This can be expensive, disruptive, invasive and a long process. 

This is a new and modern technology that can replace the need for underpinning; the process involves injecting resin into the ground to raise, re-level and re-support the building. 

It’s much less disruptive, fast, clean and cost-effective compared to traditional underpinning. 

Once your subsidence problem has been fixed, you’ll want to get any cosmetic damage repaired. For example, this may include plastering over subsidence cracks and replacing wallpaper.

Whether or not subsidence stops on its own depends on the cause. If the cause is a one-off event, such as a burst water main, then subsidence may stop on its own once the event is fixed. However, if the cause is ongoing, such as soil erosion or mining activity, then subsidence is likely to continue, and you should address the issue as soon as possible.

If you live in a house that is at risk of subsidence, then there are a couple of steps you can take to reduce the chances of your property sinking.

Firstly, keep the trees at a safe distance. Don’t plant any trees within 10 metres of your home and particularly large trees should be no closer than 40m.

Secondly, try to catch excess water. Avoid your soil from becoming waterlogged by using water butts to collect rainfall. Also, keep your guttering, pipes and plumbing well-maintained to avoid leaks.  

So what if you’re buying a house with subsidence? Here’s what you need to consider.

Get a structural survey

When you are viewing properties keep an eye out for the signs of subsidence. Ask the seller and estate agent directly if the house has suffered from subsidence. But your enquiries shouldn’t stop there. If you are interested in buying a property that you suspect may have subsidence get a full buildings survey done, and flag with the surveyor you suspect there may be signs of subsidence. The survey should inform you if there is any risk of subsidence and whether further investigation is required. Your mortgage lender’s valuation is not a survey into the condition or structure of the property so will not highlight subsidence; you will need to get a full survey done yourself.

Buying a house with minor subsidence

If you’re considering buying a house with minor subsidence you’ll still want to consider it carefully. Even if the subsidence issue isn’t particularly serious and it has been fixed, you need to reassure yourself you can get insurance as a priority. And when it comes to sell in the future, you should be prepared for the history of subsidence, no matter how minor, to put off some potential buyers.

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