As the UK continues to experience hotter, drier summers, cases of building subsidence are on the rise. Tree roots are one cause of ground movement, made worse when planted too close to properties. Certain types of trees may be more likely to cause subsidence than others, so it's worth paying attention to the types of tree species planted close to a building.

What Is Subsidence?

Subsidence is the downward movement of the ground supporting a building. When this movement is uneven, it places stress on walls and foundations, leading to visible cracks, sloping floors, or doors and windows that suddenly stick.

Common Causes of Subsidence

Subsidence is common in areas with clay-rich soils, such as London and much of the Southeast. Clay soils expand when wet and shrink when dry, creating movement that can compromise a building’s structural integrity. You can check the soil type in your area using the British Geological Survey’s online maps.

Water-thirsty trees growing near the building draw up water through the roots, leaving the soil drier and therefore more prone to shrinkage. Tree roots are just one of the common causes of subsidence, others include:

• Your soil type: different soils are affected by the shrink and swell of UK seasons, clay being the most affected

• Seasonal drying: warm and dry summers combined with wetter winters increases the risk of movement

• Local leaking and drainage: excess moisture from leaks can accumulate and shift soils

How Trees Contribute to Subsidence

Seasonal moisture variations in clay soil typically occur within the top metre of ground. For older buildings with shallow foundations, this movement alone can cause significant damage. However, where trees are present, they will absorb more water from the ground via their root system. Tree roots can draw moisture from deeper levels, sometimes several metres, meaning even newer homes with deeper foundations are not immune.

A mature tree can absorb between 500 and 2,000 litres of water per day during summer. Different species demand different amounts of water so it’s worth understanding which you have nearby to help assess the risk.

Problematic Tree Species in the UK

Some tree species are far more likely to cause subsidence than others due to their aggressive root systems and high-water uptake. See Fig 1. Some of the most common problematic species for subsidence include:

Figure 1 Information from the Association of British Insurers showing the species of trees most likely to cause subsidence, starting with Willow, and showing the safe planting distance from a building for each species

Willows (Salix species)

Weeping Willow trees are very thirsty and their root systems, which can extend up to 40m, will seek out water anywhere, which is why they are commonly found on riverbanks. It is also why their roots often find their way into drains, where they can expand and cause blockages

Poplars (Populus species)

These tall, columnar trees are fast growing with an invasive root system that is notorious for penetrating foundations in search of water.

Oaks (Quercus species)

Oaks have extensive, shallow root systems that spread far from the trunk with a very large canopy and need for a lot of water.

Horse Chestnuts (Aesculus hippocastanum)

Horse Chestnut have a high-water demand and can affect soil moisture over large areas. The ABI recommends planting at least 23m from a building.

Ash trees (Fraxinus species)

Ash trees are fast growing with a high water demands that can affect soil moisture over a large area. However, the species is in rapid decline because of Ash Dieback fungus, which is predicted to kill up to 80% of ash trees across the UK.

Maples (Acer species)

Often chosen for their highly decorative foliage, maples have a high-water demand and can affect soil moisture over a significant area.

Leylandii (Cupresso-cyoparis leylandii)

Leylandi and other cypress varieties are a popular hedging choice. Initially small hedges of Leylandii bushes may not cause a problem, they will have a much greater desiccating effect on the soil when massed together.

Signs of Tree-Related Subsidence

Tree-related subsidence often develops gradually, but early warning signs can help homeowners act before damage becomes severe. The symptoms are similar to general subsidence but tend to appear more quickly during warm, dry periods when trees take more moisture from the soil.

Common Symptoms

Tree related ground movement can show subtle signs before becoming an issue. Watch for these early warning signs around your property:

• Diagonal cracks in brickwork or plaster, often wider at the top

• Doors and windows sticking due to slight movement in the building’s frame

• Sloping or uneven floors that worsen during dry summer months

• Visible tree roots near walls, paths, or driveways

• Ground sinking in areas close to large, high water demand trees

Monitoring and Early Detection of Tree-Related Subsidence

Regularly check your property during dry spells, particularly if you have fast-growing or water-hungry species nearby. Avoid removing large trees suddenly, as this may trigger ground heave. If you notice cracks, sticking doors or other symptoms, don’t hesitate to seek advice from a specialist who can confirm whether tree roots are contributing to the problem and recommend appropriate next steps.

How to Prevent and Manage Tree-Related Subsidence

Do not plant trees close to buildings, particularly if a property is on clay soil. Figure 1 provides guidance on minimum safe planting distances for different tree species, which can be a useful resource when planning landscaping near buildings.

Tree Management Strategies

Large, mature trees can often be managed rather than removed. Techniques such as pollarding or crown thinning carried out by a qualified arborist can reduce water uptake by limiting the amount of foliage. Even simply replacing high water demand trees with lower demanding trees can help reduce the risk.

For situations where the tree must remain, root barriers can offer an effective solution. These are specially designed membranes made from heavy-duty plastic, copper, or engineered fabric, installed underground to prevent root intrusion. For best results, they should be installed by an experienced ground engineering specialist such as Mainmark UK.

Structural and Ground Solutions

If a property has already suffered from ground movement, modern remediation technologies can restore the ground's stability and level structures with minimal disruption. Mainmark UK uses innovative methods such as resin injection and screw piling, providing a faster, cleaner, and less invasive alternative to traditional underpinning.

Address the Root of the Problem

While trees bring character, shade and biodiversity to our gardens, certain species can pose a risk to foundations if planted too close to a property. Staying informed about the types of trees you have, monitoring signs of movement, and managing high-risk species proactively can help prevent costly damage.

If you’re concerned about tree roots affecting your home or have noticed early signs of subsidence, make sure to contact Mainmark’s specialists who can help assess the issue.

Frequently Asked Questions

How do tree roots cause subsidence?

Seasonal moisture variations in clay soil typically occur within the top metre of ground. For older buildings with shallow foundations, this movement alone can cause significant damage. However, where trees are present, they will absorb more water from the ground via their root system and tree roots can draw moisture from the top level and from much deeper levels, sometimes several metres, meaning even newer homes with deeper foundations are not immune.

A mature tree can absorb between 500 and 2,000 litres of water per day during summer. Different species demand different amounts of water so it’s worth understanding which you have nearby to help assess the risk.

It is also worth noting that roots can spread out at least as wide as the canopy, and sometimes up to four times the crown diameter so even if a tree appears to be a safe distance from a building, its roots could still affect the property.

Are all trees near houses bad for foundations?

Trees with a low demand for water such as Hazel, Elder, Silver Birch, Holy and Hornbeam can be planted closer to houses on clay soils, although even these species should still be planted no closer than 5m

Which tree species are the worst for subsidence?

Willows are the worst for subsidence - See Figure 1, which ranks common tree species found in the UK

How close is too close to plant a tree to my house?

This depends on the species, but even trees such as Holly, Laurel, Magnolia and Yew still have a minimum safe distance of 5m from a property

Can removing a tree fix subsidence?

No. If you suspect a tree is contributing to subsidence, do not rush to remove it. Sudden removal can cause a problem known as ground heave, where the previously dried-out soil swells as it reabsorbs moisture. This can take years to stabilise and may cause even more severe structural damage than subsidence itself.

Additionally, many trees are protected by Tree Preservation Orders (TPOs) or are located within Conservation Areas, meaning you must seek permission from your local authority before carrying out any work.

What should I do if I think a tree is causing subsidence?

Large, mature trees can often be managed rather than removed. Techniques such as pollarding or crown thinning carried out by a qualified arborist can reduce water uptake by limiting the amount of foliage.

For situations where the tree must remain, root barriers can offer an effective solution. These are specially designed membranes made from heavy-duty plastic, copper, or engineered fabric, installed underground to prevent root intrusion. For best results, they should be installed by an experienced ground engineering specialist - a service Mainmark UK is soon to launch.

If a property has already suffered from ground movement, modern remediation technologies can restore grounds stability and level structures with minimal disruption. Mainmark UK uses innovative methods such as resin injection and screw piling, providing a faster, cleaner, and less invasive alternative to traditional underpinning.