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What is subsidence and what causes it?

Subsidence is a word no homeowner wants to hear and can be a nightmare for both your and your property. At Environ Drainage Services, we work hard to make sure we can help homeowners in London avoid the costly side effects of subsidence caused by drainage problems.
What is subsidence and what causes it?
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Here’s a quick guide to understanding what subsidence is, what causes it, and what are the signs to lookout for, and how we can help!

What is subsidence?

Simply put, subsidence is the gradual caving in or sinking of the ground beneath your property. As the ground beneath your home continues to sink further, the home’s foundations subsequently begin to sink as well. This can be particularly troublesome if the ground is sinking at different rates, which can lead to the foundations of the home being misaligned and puts the very structural integrity of the property at risk. This downward movement of the property due to the ground caving in can affect the support, structure, and stability of your home.

What causes subsidence?

Subsidence itself occurs when the ground loses moisture and begins to shrink and cave in. While it may be difficult to determine what is causing subsidence without looking a bit deeper, the two main culprits are usually tree roots and drainage leaks, among others. Read below to see a full breakdown of what can cause subsidence.

Tree roots

Roots are one of the most common causes of subsidence, especially those from willow, elm and ash trees! Roots are constantly reaching for a source of water and nutrients, which often leads to them absorbing the moisture in the soil surrounding your property. The more dry the earth is beneath your home, the more likely subsidence is to occur. If this is your problem, our skilled drainage specialists are expert at tree root removal and removing trees from your premises if necessary!

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    Drain leaks and drainage problems

    Leaking drains and gutters are both prevalent sources of subsidence issues. When blocked drains or broken pipes are leaking water into the ground around your homes, it can wash away the soil beneath your home and the foundation of your property along with it, causing the ground to cave in. Our expert drainage teams are well equipped to locate the source of your drainage problems and fix them to avoid any further damage to your foundation.

    Clay soil

    Many houses built on clay soil are more likely to experience subsidence due to the very nature of clay itself. Since clay is a porous type of soil that absorbs water and shrinks when dry, it is the most likely to pull away from the foundation of a home which ultimately weakens the support. South London properties are especially prone to these types of subsidence risk since clay soil is much more common within this area.

    Weather and climate

    Soil is very susceptible to weather conditions, so when it is dry it tends to contract and when it is damp it tends to expand. When we experience long periods of rain followed by warm dry summers, the soil beneath our homes can fluctuate and become unstable. In dry weather, the ground can shrink and cave in, while areas prone to flooding can see the ground become loose from oversaturation of water and be washed away.


    Properties built in areas that were previously used for mining or quarries an also be at risk for subsidence. The ground in those areas are understandably less stable, and properties built on top of them are more likely to experience weaker and more unstable foundations.

    What are the signs of subsidence?

    There are a few key signs of subsidence that you can look out for to make sure you tackle the problem before it gets any worse. The main sign to look for are cracks throughout your property, especially those that are:

    • Wider than 3mm, or the width of a 10p coin.
    • Visible on both the outside and the inside of the property
    • Diagonal and usually wider at the top and then gradually small at the bottom
    • Located close to any doors or windows

    Cracks such as these can be caused by leaking drains, tree roots, or any of the reasons detailed above. When you notice these cracks, it is important to determine what is causing them.


    How Environ Drainage Services can help!

    At Environ Drainage Services, our experienced drainage experts are on hand to determine if tree root ingress, blocked drainage or damaged guttering causing water leaks are the source of your subsidence issues! We have skilled surveyors who can locate the source of any leakages that can be causing subsidence, and using a CCTV drain survey, our experts can spot any cracked drains or tree root ingress. From there, we can provide our expert recommendations for any remedial works that need to be undertaken to stop the drainage issue and the subsequent subsidence that it may be causing.

    If our surveyor determines that the issue is coming from tree root ingress, we can suggest to cut them out of the drains themselves, and then restore your drains to full working condition using our patch repair techniques. If the cause is leaking drains, we can flush out any blockages using our high power pressure jetters, and then use a CCTV drain survey to locate the precise location of the leak. Similarly, we will then repair your drains to prevent any further leakages. It is important to fix the root of the subsidence problem before fixing the cosmetic cracks in your walls, to avoid the costly and more damaging issues in the future!

    Call our friendly staff today to set up a time for one of our professional surveyors to come out to your property and determine if drainage issues are causing your subsidence!

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