How do trees contribute to subsidence?

As tree roots spread, they take up moisture from the soil to support the tree’s growth. In some soils, that moisture loss causes the ground to shrink, which can lead to subsidence. How much risk this creates depends on several factors:

Soil type: clay is more vulnerable than sandy or chalky soils, as it shrinks during prolonged hot and dry weather, and swells when wet.

Tree species: larger, thirstier trees such as willows and poplars take more water from the ground. A mature tree can absorb anything between 500 and 2,000 litres of water a day.

Root distribution: some trees have far-reaching roots, so they can affect the ground a long way from the trunk. Willow tree roots can extend up to 40m from the tree.

Weather conditions: consistently dry weather can cause clay soils to lose their moisture and shrink, potentially leading to ground movement. Roots searching for whatever moisture is left can make this movement worse.

Foundation depth: shallow foundations in clay soils are more at risk because they sit in the top layer of soil, which is where most roots take up water.

That said, not all trees pose a subsidence risk. Understanding what trees you have near your home, and their characteristics can help determine if your property is at risk.

Why tree removal isn’t that simple

Removing an offending tree may seem like the obvious solution, but it’s not as straightforward as it appears. Tree felling can introduce other challenges.

Trees may be protected by tree preservation orders (TPOs), which means consent is generally required from your local council before any work starts.

Established trees also provide habitats for wildlife, playing a vital role in biodiversity and the local ecosystem. They offer shade, urban cooling and carbon storage, whilst enhancing the character of streetscapes and public spaces.

If a tree is removed, there is a potential risk of further ground movement, especially in areas with clay-rich soils. In certain cases, when the moisture returns, it can cause the ground to swell in a process known as heave.

Felling a tree may not be the best way to deal with a subsidence problem. A more targeted approach can help protect the property and preserve the local tree at the same time.

The role of engineered tree root barriers

In appropriate circumstances, a tree root barrier can be an effective solution that manages the interaction between the tree roots and vulnerable ground. Due to the change of weather, removing trees creates high risks during the wet season as they help to manage the waterlogged ground, with their roots working as a binder too. A geosynthetic textile root barrier allows for the moisture to move through it without creating two different moisture zones, unlike uPVC or concrete.

This barrier is a physical membrane, typically made of heavy-duty plastic, copper or engineered fabric, that’s installed below ground to form an obstruction. In copper root barriers, the copper ions naturally discourage root growth at their tips, helping to redirect the roots away from foundations and structures.

Root barriers are designed to limit root intrusion while preserving the health of the tree. On their own, though, they may not be suitable where roots have already caused significant structural damage and further remedial work is needed. Therefore, identifying the risk of tree-related subsidence early is essential in helping to prevent further, more costly damage.

Getting an early assessment

If you suspect tree-related subsidence on your property, arranging for a professional assessment as early as possible can help prevent further damage and identify the best remedial work.

Early warning signs such as long, widening cracks in walls, sticking doors and windows or emerging gaps around extensions can have several causes, so they shouldn’t automatically be put down to trees. 

A full site investigation, usually carried out by a geotechnical specialist, will typically involve trial pits and boreholes to examine the building’s foundations, the underlying geology, soil conditions and the level of risk posed by surrounding trees.

With prolonged hot, dry spells likely to become more frequent, proactive assessments can help homeowners protect their properties. Homeowners can benefit from a free visual site inspection from Mainmark UK. To book, contact us today.

Protecting properties, keeping trees standing

Whilst tree removal may sometimes be necessary, it’s important to know about the other options available. In some cases, engineered tree root barriers can offer a targeted alternative, which helps manage the risk of root damage while preserving established trees.

Mainmark UK can help homeowners understand ground movement challenges and identify appropriate ways to protect their properties. By looking at the cause early rather than simply removing the offending tree, it’s possible to manage tree-related subsidence effectively without compromising the local vegetation.

If you’re looking for more information on how Mainmark UK can help you or to book a free visual site inspection, speak to an expert today.