Buying a house with subsidence
Are you considering buying a house with subsidence? Or perhaps you’re hoping to sell your property and are worried about some cracks that have begun to appear? Subsidence is a scary word for any homeowner or prospective buyer, but it is estimated that around 40,000 properties are affected by subsidence each year.
In this guide
- What is house subsidence?
- Should you buy a house with subsidence?
- What’s the difference between subsidence and settlement?
- Signs of subsidence
- Subsidence warning signs to look out for
- What is underpinning?
- How much does subsidence devalue a property?
- What can you do if your house has subsidence?
- Selling a house with subsidence history
What is house subsidence?
Subsidence is the downward movement or collapse of the ground that a property sits on.
All properties will experience a small amount of movement, which will largely go unnoticed, but sometimes that movement occurs in a downward direction, causing the property to become unstable. When this happens it is important to take action to protect the property from extensive damage.
Should you buy a house with subsidence?
If you’re considering buying a house with subsidence history, your first step should be to gather more information about the current condition of the property. If the problem is a historic one that has been treated,it’s important to gather all of the paperwork you can from the seller. It is also advisable to ensure you have a thorough structural survey carried out before proceeding with a purchase. If subsidence may be a current issue at the property, a full structural survey will assess the severity of the issue and advise on work required to address the problem.
Properties with current subsidence will be unmortgageable, so if you were planning to use a mortgage to purchase the property it’s unlikely that you’ll be able to go ahead.Properties with a history of subsidence that has now been fully resolved are often challenging to mortgage and insure, but it is possible. The Subsidence Claims Advisory Bureau (SCAB) specialises in assisting people who live in or are considering buying properties that have suffered from subsidence. They can help with securing mortgage lending and comprehensive insurance, as well as offering advice on many other aspects of owning a house with a history of subsidence.
What’s the difference between subsidence and settlement?
Most newly-built properties will experience some degree of settlement. Settlement is caused by the ground beneath the property compacting under the weight of the new structure.
Unlike settlement, subsidence is not caused by the weight of the building, but by the ground beneath the property becoming unstable. Subsidence would have occurred whether the property was on the land or not.
Properties can also experience ‘heave’, which is where the ground beneath the property swells and moves in the upwards motion.
Signs of subsidence
Early signs of subsidence may include torn wallpaper or windows and doors that are starting to stick, but the most obvious sign of subsidence is the appearance of substantial cracks in your walls. When the ground beneath your property becomes unstable and moves in a downward motion it will take some of your property’s foundations with it. As one section of your property begins to move it will put pressure on the structure of your home and cracks will begin to show at the point of tension.
It is important to note, however, that cracks are not always a sign of subsidence. Small hairline cracks that appear seasonally are likely to be due to the expansion or contraction of materials caused by changing weather, which is not something to be overly concerned about. Cracks that are a result of subsidence will usually be large (thicker than 2mm) and visible internally and externally. You would also suspect any cracks caused by subsidence to be wider at one end and often diagonal in direction.
Subsidence warning signs to look out for
There are several things that can put a property at increased risk of subsidence. These include:
- Large trees close to a property
Large trees close to properties can cause problems with the stability of the property’s foundations. Large tree roots can disturb the soil beneath the foundations and thirsty pants can dry out the ground, leaving it more vulnerable to cracking and movement.
- Older foundations
Older properties tend to have shallower foundations, which may leave them more susceptible to erosion and subsidence
- Clay soil
It is estimated that around 80 percent of subsidence claims involve clay soil. Clay soil is particularly prone to cracking, shrinking and moving during warmer, drier weather. This then unsettles property foundations and causes subsidence. A good way to assess whether clay soil is likely to cause a problem is to look closely at surrounding properties for any sign of external cracks.
- Water leaks
Any damaged water mains or household drains can create an added subsidence risk over time. Soil that becomes saturated with water can easily become unstable and erode under the weight of a property.
- Nearby mining history
Any area that has a history of mining has an increased risk of experiencing subsidence. It is important to gather information about any historic mining activity as part of your pre-purchase property searches so that you can take any necessary steps if the property is at risk.
What is underpinning?
Underpinning a house is the process of strengthening foundations that has been affected by subsidence.
Underpinning costs will vary depending on the severity of the subsidence and the method of underpinning required to resolve the issue.
There are several different types of underpinning, including:
- Mass concrete underpinning
Mass concrete underpinning is a way of extending or deepening existing foundations and is the most common method of property underpinning. Areas of ground beneath the existing foundations will be excavated and then filled with concrete. This process is completed in small, manageable sections to ensure the property remains well supported while the work is carried out.
Piling is seen as the most versatile method of strengthening a property’s foundations. Piles are driven into the ground, bypassing the weaker, looser soil, to sit on more stable soil or bedrock below.
- Jet grouting
Jet grouting can be used to strengthen weak soil beneath the existing property foundations. High-pressure jets are used to mix existing soil with a self-hardening grout, creating a strong, substantial base to support the property’s foundations.
Underpinning used to be routine when resolving subsidence issues, but now tends to be used as a last resort for more severe subsidence. Buying an underpinned house should offer reassurance that any previous subsidence issue has been resolved. In fact, an underpinned house is usually substantially more robust and stable than a property that has never experienced any issues with subsidence.
How much does subsidence devalue a property?
How much subsidence devalues a property will depend on how severe and recent the problem is, but a property that has previously been underpinned to address an issue with subsidence is estimated to be worth around 20 percent less than a similar property without any history of subsidence.
What can you do if your house has subsidence?
If you suspect subsidence, your first step should be to contact a chartered surveyor to assess the severity of the problem. Unfortunately this is not always a quick process as any cracks or movement may need to be measured and monitored for a number of months. If subsidence is confirmed, the cause will need to be identified and addressed.
Selling a house with subsidence history
If your property has a history of house subsidence that has been dealt with effectively, it’s important that you keep any relevant paperwork and make it readily available to any prospective buyers.
If you’ve experienced subsidence, insurance and mortgages can be more challenging to secure. This will undoubtedly put some buyers off. If you bought a house with subsidence history yourself, you’ll be aware of the challenges. This means you may be able to reassure any prospective buyers. If the subsidence has occurred while you’ve owned the property, ensure you are open and forthcoming with information about the root cause of the issue and how it has been dealt with.
Unfortunately, even if the subsidence has been dealt with and no longer poses any problem, there are some prospective buyers that will still be nervous about moving ahead with purchasing the property. It’s important to be upfront about the historic problem and how it has been resolved, as subsidence – even historic – is something that will show up in a property survey.
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