In recent years the UK has been subject to periods of extreme hot and dry weather, putting properties at greater risk from subsidence.
Subsidence happens when the ground under a property collapses 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 we had in 2022 it is known in the insurance industry as an “Event Year”. Lots of trees have been left to grow unabated as people assume they aren’t causing any 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, which means they can drink huge amounts of water each day and dry out gardens. Mature trees may remove more than 50,000 litres out of 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, which is 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 has 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 an option to cover damage caused by subsidence, but this might not have been selected.
Beware of the following subsidence myths
Myth 1: 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 2: 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, which is usually a tree or a shrub. Underpinning is only a last resort when we cannot stabilise by other means.
Myth 3: 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 4: Large thick roots are the problem
It’s the fibrous, hair roots at the extremes of the root system that 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 them, maintain them, reduce them, clip them 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 important to check that your Local Council insurance policy provides cover for Subsidence. This cover can be added onto your Councils policy, subject to underwriting. If you are unsure whether your policy provides this cover then please contact your insurance provider for clarification.
