What is Subsidence and What Impact Does it Have?
Subsidence refers to a building that’s sinking into its foundations. It can stop a proposed property sale in its tracks and cost thousands to fix. But, if you know what you’re looking for, spotting the signs early makes all the difference! So, what is subsidence? What impact does it have? What can you do about it? Let’s take a closer look.
Subsidence definition
It occurs when the ground beneath the foundations of your property become unstable. The result of this is that your home begins to sink unevenly into the ground. If you’ve seen old properties propped up for months with scaffolding, this is often the culprit. However, all homes are at risk of subsidence – not just older buildings.
What causes subsidence?
The most common causes of house subsidence are:
- Clay soil beneath the building shrinking during dry weather, making the foundations unstable
- Vibrations from the ground on which the property sits
- Tree roots causing soil shrinkage by extracting water
- Leaking drains or pipe blockages causing an overflow, resulting in soft ground
- Disused mines or other excavations underneath the property
Signs to look out for
Usually, cracks are the biggest sign of subsidence. However, it’s also important not to jump to conclusions. Cracks can occur due to temperature, as your house shrinks and swells due to heat changes.
Also, if your home is a new-build or has been freshly painted, minor splits can occur in the plaster naturally.
But, there are ways to the difference. So, what do subsidence cracks look like? They will be:
- Usually bigger than 3mm
- Noticeable from both the inside and the outside
- Diagonal
- Usually found near doors and windows
- Wider at the top than the bottom
These could be on the walls, ceilings or external brickwork though they normally appear at ‘weak points’, such as around windows and door frames or where an extension has been added. It’s a good idea to keep an eye on these cracks and take action if you see them getting bigger.
Other tell-tale house subsidence signs include:
- Doors and windows sticking or being tough to open
- Rippling wallpaper (which you’re sure isn’t the result of damp)
What to do if you spot warning signs
Don’t panic, but take action! The sooner it’s fixed, the less damage will be done to the property.
Find a surveyor and arrange an inspection of your property. They’ll be able to tell you whether they believe the building has subsidence and then advise on what remedial action can be taken.
This can involve measuring and monitoring the cracks long-term (this can often be up to a year). You can also prevent the problem with regular pruning of nearby trees and shrubs. Take care to avoid leaks also, as this can make the problem worse.
How to treat subsidence
Depending on how bad the problem is, there are a few different options you and your surveyor can choose to treat it. These include:
- Stop overflowing water by repairing damaged drains or pipe work
- Remove or prune any offending trees, including taking up the roots (these can continue to grow even after a tree is felled)
- Once you’ve tackled the cause of the subsidence, you can then underpin the problem area of the building
Underpinning the foundations means digging deeper into the ground and adding support to existing foundations in an effort to prevent the building moving down further. This takes time to carry out and can prove very expensive.
Sort out insurance
Once your property is treated, subsidence shouldn’t recur. Some home insurance policies cover the work of rectifying subsidence. If it is covered, the insurance company will send a specialist (often an independent structural engineer) to inspect the problem.
This isn’t the case will all home insurance covers – so be sure to check your plan and contact your insurer. The cost of your insurance claim will depend on the severity of the problem.
Should you buy a house with subsidence?
What happens if your property survey reveals some inconvenient truths? Depending on the type of property survey you choose, it should reveal subsidence.
Buying a house with structural problems is an enormous concern. It can severely impact the resale price of a property due to the cost of repairs.
But, should you be concerned about a home that has previously had this issue?
If a property you’re thinking about buying has been treated for subsidence in the past, the owner should have a Completion Certificate showing it has been underpinned (if relevant) and a Certificate of Structural Adequacy. The latter is issued by a building surveyor for an insurer.
The Coal Authority also has a database of claims to give you peace of mind.
It’s important to check you can get insurance for the property, some companies don’t like to insure previously underpinned properties. This will prevent you getting a mortgage. Most insurance providers should be reasonable if the cause of the subsidence has been tackled. Some companies, can offer specialist insurance advice for properties that have been underpinned.
Be aware before you buy
If there’s no history of subsidence in a property but you suspect it may be a problem in the future, an independent HomeBuyer Report and Building Survey should highlight this.
When buying a property, consider the type of soil it has been built on (the more clay-based, the more prone the building is to subsidence). Look for signs of cracks (internal or external) that have been painted over or ‘touched-up’. Keep an eye out for large trees close to the building.
If you already own a property, preventative maintenance is the key to keeping subsidence at bay. Remove any large plants or shrubs sitting close to the building and ensure you maintain drains, pipes and gutters.
Get a good surveyor
Don’t get that sinking feeling! You need a good surveyor to assess the property so you know what you’re spending your money on is structurally sound. If you spot the early signs, get a professional opinion. Get your free survey quote below.
Last Updated: November 1st, 2024
