Can Blocked Drains Cause Subsidence?

Subsidence is quite a common and serious problem for many homes in the UK. This is partly due to the soil structure but can also be a result of the increased weight placed on the ground from large buildings in close proximity to each other. But, can blocked drains cause subsidence?

Although blocked drains may not directly cause subsidence, they can contribute to problems that are generally regarded as the major causes of subsidence. If drains are blocked, it often means that surface water cannot drain away and will, therefore, pool around the foundations of your home.

Additionally, blocked drains can break or split and can also be an attractant to tree roots that will eventually damage the drain pipes. All of this leads to excess water on the ground and thus, subsidence can be a real problem.


What Is Subsidence?


Put quite simply, subsidence is the result of the ground sinking beneath the foundations of your home. This, in turn, weakens the foundations as well as your home’s support and structure.

This sinking can either be the result of too much water in the soil, especially during periods of heavy rainfall, or that the ground is too dry. In certain soils, when there is a lack of moisture, the soil will often crack and shrink.

Subsidence can be a serious problems as it affects the integrity of the home and can result in large cracks in the walls as well as more dangerous problems associated with the entire structure of the house.

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    What Causes Subsidence?


    There are a variety of factors that can cause subsidence to your home. These include:

    • The type of soil. Clay soils are particularly prone to subsidence. Because the clay is porous, it will shrink when it becomes dry. This means it can pull away from around your foundations. On the other hand, sandy soils can easily be washed away from around the foundations during periods of heavy rainfall.
    • Invading tree roots. The roots of larger deciduous trees such as oaks, elms, willow and ash, can easily grow close to or under your home as they search for moisture. When this happens, the soil will become dry and possibly shrink away from your foundations.
    • Drains that are leaking, broken or blocked. When your drainage system is not functioning as it should, leaking, broken or blocked drains can add to the problem of subsidence. Any excess water that gathers under your home is a concern as it can saturate the soil and disrupt its structure. Sandy and gravelly soils can easily get washed away and this can cause your foundations to sink.
    • Previously mined areas. If homes are built on top of ground that has previously been mined, there’s a strong danger of subsidence occurring as the soil fills in the gaps that may still be there deep under the ground.



    How Do Your Know If You Have A Problem With Subsidence?


    There are many telltale signs that can alert you to the fact that your foundations may be weakened and are sinking into the ground. These include:

    • You notice cracks appearing both inside and outside on your brick walls.
    • These cracks will often spread diagonally across the wall.
    • You may also notice cracks at various wall joints especially where an extension has been added.
    • There may be cracks close to the windows and doors of your home.
    • You should take note of cracks that are expanding rapidly.
    • If your windows or doors became harder to open or close or begin the stick.
    • If you have wallpaper on your interior walls, this may start to form ripples, especially at the joints.


    What Should You Do If You Suspect That Your Home Is Subsiding?


    The first thing you should do is try to work out what is causing the subsidence. If you suspect that it may be a problem with your drainage system, you should book a CCTV drain survey as soon as possible. This drain survey will let you know whether there are any problems that can be identified within the network of drain pipes underneath your home.

    If the survey indicates that there is a problem with your drains, this can be repaired and will ensure that the foundations of your home don’t suffer any more damage.

    You should also get help from a surveyor who will be able to undertake a structural survey. This should give you an indication as to the extent of the damage and what measures should be taken to rectify it and avoid any future problems.



    What Are The Most Common Solutions To Fixing Subsidence Problems?


    The most appropriate solution to your subsidence problem depends entirely on the cause of the problem in the first place. Here are the most common solutions:

    • Leaking, broken or blocked drains. Your drains should be thoroughly inspected and any problems should be fixed as soon as possible. It’s then important to have your drainage system inspected regularly to ensure that the problems don’t recur in the future.
    • Tree roots. If you believe that tree roots may be causing the ground to sink, then it could be prudent to have these trees removed as they pose a danger to the structural integrity of your home.
    • Underpinning. If the problem of subsidence is quite severe, you may need to have your house underpinned. This involves adding extra foundations to help to strengthen the structural integrity of your home.


    Final Thoughts


    Blocked, leaking and broken drains can certainly add to the problem of subsidence. If your drainage system is not doing the job that it is designed for correctly, you could end up with excess water pooling around your foundations.

    This excess amount of water can either over-saturate the soil and make it unstable or, in the case of sandy or gravelly soils, it can wash away the soil from around your foundations.

    If you suspect that there may be a problem with your drainage system, it’s best to book a CCTV drain survey as soon as possible so that any problems can be rectified before any more damage occurs.

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