How can I be more aware of subsidence?

Author: Lee​ Cleaver, sales development account broker at BHIB Councils Insurance 

In recent years the UK has been subject to extremely hot and dry weather, putting properties at greater risk of subsidence.

Subsidence happens when the ground under a property collapse or sinks lower. This uneven movement may result in structural damage, such as cracks in walls, floors, and ceilings, which can be expensive to repair.

Causes of subsidence

Properties built on clay soil, which shrinks when there is less moisture in the ground, are particularly at risk of subsidence in a prolonged dry spell. Trees and large vegetation are also generally involved. Their roots take water from the soil, drying it out and causing it to shrink even more.

When the UK gets a long, hot and dry summer, such as in 2022, it is known as an “Event Year” in the insurance industry. Many trees have been left to grow unabated as people assume they aren’t causing damage. Therefore, there is a possibility that potential problems have been created and will be unleashed during the next inevitable dry year.

Poplars, willows, and oaks are among the worst culprits as they have long, fine root structures, meaning they can drink massive amounts of water daily and dry out gardens. Mature trees may remove more than 50,000 litres from the ground each year.

Another cause of subsidence is water leaking into the soil from damaged drains, washing soil away from a building’s foundations.

How to spot subsidence and what to do about it

The tell-tale sign of subsidence is a diagonal crack next to a door or window, often narrow at the bottom and wider at the top. Look out for cracks that can be seen on both the inside and outside of the property. If they are underneath wallpaper, they may cause it to wrinkle.

Some movement in a property’s foundation is normal and won’t necessarily cause damage. Likewise, it is normal for some properties to have minor cracks which have nothing to do with subsidence.

If you are concerned about a crack, ask yourself: “Has it been there for a long time, or has it just appeared? Is the crack in just the plaster, or is it going behind into the structure, through the wall and onto the other side?” In that case, it could be the beginning of subsidence.

In the winter, when there is frequent rainfall, the cracks may start to close again, but the problem will come back again the following summer unless the underlying cause is dealt with.

The important thing is to call your broker if you are concerned. Most policies will have the option to cover damage caused by subsidence, but this might not have been selected.

Beware of the following subsidence myths

Myth one: Removing a problem tree could cause more extensive damage

The removal of trees causes problems in less than one in 1,000 cases. There’s more chance of a problem tree causing damage by leaving it there. Nor does it help to remove the tree in stages – if the tree is the cause of the soil shrinkage, it is generally prudent to remove the tree. You don’t have to remove roots; you just have to kill the tree.

Myth two: Underpinning (strengthening the building’s foundations) is the answer

Underpinning is often not the right solution. Why would you want to throw a bit of concrete under one part of the house? It fails because people take their minds off the cause, usually a tree or a shrub. Underpinning is only a last resort when we cannot stabilise by other means.

Myth three: Trees with a Tree Preservation Order (TPO) can’t be removed

When a tree has a TPO, it just means you need approval from the council to remove it. It doesn’t mean you can’t do it.

Myth four: Large thick roots are the problem

The fibrous, hair roots at the extremes of the root system take the water rather than the big primary roots.

So how can I reduce the risks?

If you are aware of the potential problem, there are some simple steps you can take to limit the risks:

• If you have trees on your land, take responsibility for them. Manage, maintain, reduce, clip, and control them.
• Don’t plant inappropriate trees too close to your home, garage or outbuildings. The Association of British Insurers (ABI) suggests willows need to be no closer than 40m from the nearest building, poplars 35m away, and oaks and elms 30m away.
• If you’re unsure whether a tree could cause damage, seek professional advice.

• Check whether your current property insurance policy covers you for subsidence risks, and if not, make sure that it is included at your next renewal. 

Are you covered?

It is essential to check that your local council insurance policy covers Subsidence. This cover can be added to your councils policy, subject to underwriting. If you are unsure whether your policy provides this cover, don't hesitate to contact your provider for clarification.

If you have any questions or queries on any of these topical matters, please get in touch with BHIB Councils Insurance for further information at .

The following blog post is for informational purposes only and should not be considered professional or legal advice. The views and opinions expressed in this post are those of the author and do not reflect the official policy or position of the National Association of Local Councils. Any links to external sources included in this blog post are provided for convenience and do not constitute endorsement or approval of those websites' content, products, services, or policies. Therefore, readers should use discretion and judgment when applying the information to their circumstances. Finally, this blog post may be updated or revised without notice.