How Trees & Dry Weather Cause Subsidence | Geobear

Written by Aleister Willis | Jun 4, 2025 9:15:00 PM

How Trees and Dry Weather Cause Subsidence: A Homeowner’s Guide

If you live in a part of the UK built on clay soils, particularly in the south and east, your home could be at risk of subsidence, especially during long, dry summers. This guide explains the science behind the problem, why certain trees make it worse, and what you, as a homeowner, can do to protect your property.

What Is Subsidence and Why Does It Happen?

Subsidence occurs when the ground beneath a building sinks, causing the structure to move. On shrink-swell clay soils, this is most often caused by the soil drying out and shrinking. During hot summers, two things accelerate this process:

Evaporation: Water evaporates from the soil surface
Transpiration: Trees and plants draw moisture from the soil through their roots and release it through their leaves

Together, these processes are called evapotranspiration, and they can remove large amounts of water from the soil, causing it to shrink

How Trees Affect Soil Moisture and Foundation Movement

Tree roots naturally seek out moisture. In dry conditions, they grow deeper and wider, especially in clay-rich soils. Many UK homes have shallow foundations (often less than 1 metre deep), which puts them at risk when deep-rooted trees nearby draw moisture from the soil beneath.

This causes the clay to shrink and the ground to sink unevenly, resulting in cracks in walls, sticking doors, and other structural issues.

Tree Species with the Highest Risk

Some trees have much higher water demands and more aggressive root systems. Here are the top 10 trees most likely to cause subsidence on clay soils:

Tree Species	Water Demand	Root Spread	Typical Depth	Subsidence Risk	Min. Distance from Buildings
Poplar	Very High	Up to 40m	2–3m	Very High	40m+
Willow	Extremely High	30–40m	2–4m	Very High	35–40m
Oak	High	Up to 30m	3–5m	High	25–30m
Horse Chestnut	High	25–30m	~2m	High	25–30m
London Plane	Moderate–High	20–25m	Moderate	High	20–25m
Elm	High	Up to 30m	Moderate–Deep	High	25–30m
Sycamore	Moderate	20–25m	Moderate	Mod–High	20m+
Ash	Moderate	20–30m	Moderate–Deep	Mod–High	20–25m
Beech	Moderate	Up to 20m	Shallow	Moderate	15–20m
Birch	Moderate	15–20m	Shallow	Moderate	15–20m

What Can Homeowners Do?

1. Manage Trees Wisely

Avoid planting high-risk species near your home
Regularly prune large trees to reduce their water demand
Consider removing problematic trees – but always seek professional advice to avoid sudden ground movement (\”heave\”)
Check with your local authority if trees are protected

2. Understand Your Soil and Trees

Use online tools (like Soilscapes) to check if you’re on shrinkable clay
Measure the distance of nearby trees from your property

3. Watch for Warning Signs

Cracks wider than 3mm, especially diagonally above windows or doors
Doors or windows sticking
Gaps are opening between walls and skirting boards

4. Get Professional Advice Early

Contact a structural engineer or a specialist subsidence company like Geobear
Don’t wait – early intervention can prevent costly repairs

5. Check Your Insurance

Make sure your building’s insurance covers subsidence
Inform your insurer of any tree management near your property

6. Be Aware of Heave Risk

Removing a mature tree can cause the clay to rehydrate and swell
Always get an expert opinion before tree removal

7. Use Geobear’s Free Assessment

Geobear offers free, no-obligation assessments for homeowners worried about subsidence. Our geopolymer injection process can improve ground conditions and remediate subsidence issues without excavation, often in just one day.

In Summary

Hot, dry summers and thirsty tree roots are a major trigger for clay shrinkage subsidence in UK homes. But with awareness, preventative steps, and expert help, you can manage the risk and protect your property.

Need help assessing cracks or subsidence risk? Contact Geobear today for a free assessment.

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