Home » Clay Shrinkage Subsidence

Clay shrinkage subsidence accounts for roughly 70% of all subsidence cases in and around the United Kingdom, with trees and dense, heavy vegetation or foliage being the root cause of the issue that many homeowners fear. But what exactly is clay shrinkage and how are trees responsible for it happening in the first place?

What is clay shrinkage subsidence and how is it caused?

Clay shrinkage subsidence occurs when nearby tree roots extract the majority of the moisture from the ground during the warm, dry summer months. The subsequent lack of water in the ground will cause the clay to shrink and, in turn, cause the foundations underneath the building to shift. 

As the autumn and winter months roll around, the moisture will return, causing the foundations to move upwards as opposed to downwards, as it did the summer. The danger here is that the foundations could keep moving up and down seasonally, which could make the subsidence significantly worse and a lot harder to rectify as the years go on – this is called ‘Seasonal Movement’.

Therefore, it’s important that a suitable subsidence solution is found before further damage, that would have otherwise been preventable, is done. In order for the issue to be resolved as effectively as possible, a soil investigation must be done before any work can be carried out. Where there are some who would opt out of having a soil investigation conducted, it’s actually a vital step in the overall process, hence why it’s highly advised by the experts to have one carried out. 

Tree root subsidence diagram

Soil investigation: what is it and why is it important?

A soil investigation allows the engineers to determine, as accurately as possible, the depth of the deepest roots in order to resolve the problem effectively. If you opt-out of having a soil investigation done, work will be carried out based on assumptions rather than the factual information that will always be used for verification.

If the treatment then doesn’t extend far, or deep enough to reach the cause of the problem, then the surrounding clay will still have the potential to continue shrinking, making it highly likely that the subsidence will, eventually, reoccur. This means is very important that a soil investigation be conducted prior to work being carried out.

What does a soil investigation consist of?

  • A trial pit will be used to help determine the number of important factors, including depth, thickness and foundation type
  • A borehole will be constructed either 3 or 5 metres below ground level. This will help to establish how strong the clay is, its moisture content and its likelihood of shrinking. It will also help to identify the depths of the deepest roots that now sit below the foundations, making it a fundamental part of the overall process as it will establish where the unstable ground ends and the competent soil starts

Geobear have a highly-effective, non-disruptive solution

Illustration of tree roots beneath foundation with geopolymer

Geobear has an extremely effective solution to clay shrinkage subsidence that has been specifically designed and engineered to be non-disruptive, highly-successful every single time. This particular procedure differs somewhat from how other causes of subsidence would be dealt with, such as drain failures for instance.

Geobear has revolutionised the way in which clay shrinkage subsidence can be rectified, all with the innovative geopolymer (resin) injection method. Firstly, the geopolymer is injected into the ground below the deepest tree or plant roots that are causing the problem. The resin will continue to be injected at various levels until the underside of the foundations has been reached.

Almost immediately, the resin will begin to flow into all the cracks and fissures, no matter how big or small they may be. This will help to prevent moisture from getting in and subsequently being extracted from the clay as the seasons change. In turn, this will reduce the risk of shrinking and swelling considerably, making it the most ideal solution to your clay shrinkage subsidence problem.

The benefits of the geopolymer injection method

  • It’s non-disruptive – our engineers won’t need to gain internal access to your home in order for work to be carried out
  • It saves time – it’s a fast-working process that can usually be completed within two days at the most, whereas traditional methods may take weeks
  • It’s mess-free – our engineers carry out their work precisely and meticulously, meaning that the surrounding ground will be undisturbed as an excavation won’t be necessary with this procedure
  • Eliminates need to cut down offending trees and foliage – it protects plant life which, in turn, will help the environment

Related projects