Subsidence: what do you need to look out for?

Not all cracks necessarily mean subsidence. For example, new build properties settle overtime, and buildings naturally shrink and swell to a degree, which can cause fine ‘hairline’ cracks. These types of cracks are normally uniform in width, and up to 3mm wide (7).

Cracks which should have further investigation however, include:

• Cracks which are 3mm+ in width
• Diagonal/stepped cracking
• Cracks which are not uniform in width (e.g. wider at the top than the bottom)
• Cracks seen from both inside and outside
• Cracks which occur near doors or windows. (4).

Other things to look out for include cracks which blow the damp proof course (10), warping around doors so they don’t close properly or start sticking, and cracking where extensions join the original property.

What should I do if my home is showing signs of subsidence?

If you notice anything that causes concern, it’s best to get these checked by a structural engineer. Engineers may install monitoring equipment to track changes over time.

If remedial work is required, depending on severity, this could involve underpinning, drainage repairs, or tree removal. Remember to keep a record of repairs for insurance and future property sales.

What can I do to help prevent subsidence at my property?

Maintain trees and shrubs. As trees and shrubs remove moisture from the soil, when they are close to the building they can contribute to subsidence in certain soil types. Maintaining trees stops them from becoming too large, meaning their water intake is maintained and the surrounding soil doesn’t become drier (9).

Removal of a tree can cause the opposite problem, with there being an increased level of water in the soil, causing the ground to “heave”. We would always recommend seeking advice from an arboriculturist.

If you have a tree with a Tree Protection Order, its important you don’t carry out any works without Council consent.

Consider your planting. Different trees have different uptakes of water. This means that some trees are better suited to clay rich soil, as they don’t dry the soil out as much. The silver birch, holly, and hornbeam for example all take up a lower rate of water, whereas oak trees, elm and willow are all high water intake trees (8) and therefore give a higher risk of drying out the soils around them. If you’re looking to add plants to your garden, you could consider a less “thirsty” tree.

Regardless of the tree, it is still wise not to plant too close to your building. Generally, if the tree is taller than the distance from the house, it’s likely the root system will spread beneath the property (5). Removing trees which are older than the property, however, can also cause issues so its recommended that these aren’t removed if possible (10).

For more advice on tree maintenance and what insurers will consider, please read our article: Trees and your property: insurance consideration.

Leaking pipes, drains, gutters and downpipes. As well as the weather affecting the ground moisture, leaking drains can have a similar effect. Soil around a leak (especially in sandy soils) can soften or begin to wash away, so that the ground sinks and potentially the foundations too (9). If you notice a leak, damp patches on your walls, pooling of water anywhere, or unexpected changes in your water usage, it’s best to get this checked.

My property has had subsidence repairs – what should I do?

If your property has had subsidence, an up-to-date structural engineer’s report can be beneficial, it may even be an insurer’s requirement, especially if this confirms the property is now structurally stable and any movement historic.

If you’re thinking of buying a property with a history of movement, ask for a Certificate of Structural Adequacy or a Structural Engineer’s Report which shows that the cause of the movement has been removed, that any cracks have been properly filled, and that the superstructure is now sound.

New measures for subsidence

As research continues, there are new methods being trialled to remedy subsidence.

Electro-kinesis Stabilisation (EKS) for example is currently being trialled as a method to resolving tree root related subsidence by treating clay soil so that it no longer ‘Shrink-Swells’ significantly, rather than removing trees or underpinning the property. This method takes about 2 weeks and involves passing an electrical current through metal tubes into the ground; to introduce electrolytes into the soil and change the soil structure so it is no longer drastically affected by the presence/absence of moisture. (11) As this treatment of the soil is permanent, this would offer a long term, minimal disruption solution to subsidence, which is also environmentally friendly (with no trees being removed) & at a lower cost than underpinning.  

Subsidence insurance

Obtaining home insurance for a property that has previously been affected by subsidence can be difficult. We understand the challenges of subsidence and historic movement and can negotiate with insurers on your behalf.

To speak to us about your home insurance call 020 8256 4901, request a call back, or email privateclients@howdeninsurance.co.uk

References
1. Innovation Group - Technical Bulletin - May 2025
2. The CII - Predicting and preparing for the increasing risk of subsidence
3. ABI - Subsidence | ABI
4. British Geological S Swelling and shrinking soils - British Geological Survey
5. Subsidence risks for properties in London - Structural Engineers Report
6. Subsidence 'surge years' create waves of major insurance claims, reveals IStructE guide
7. n/a
8. Subsidence and Trees - Woodland Trust - Woodland Trust
9. Subsidence and trees - how to avoid that sinking feeling - Aviva plc
10. Loss Prevention Council Information Sheet
11. Innovation Group - Technical Bulletin – April 2025
12. Innovation Group - Technical Bulletin – February 2025