Should I buy a house with a history of subsidence?

Subsidence – the ground itself sinking and causing a house to go with it – sounds terrifying, like something from a disaster movie. Yet it’s more common than most of us like to believe and something home surveys occasionally pick up on. When you buy a house, it’s absolutely crucial to discover as many of its defects as possible before committing to the sale. Home surveys help with this hugely. Subsidence is something home surveys might pick up, whether current or historic. So, is it an immediate deal-breaker? Or not?

What is subsidence?

Subsidence is when the ground underneath a property sinks. A bit like your heart when you hear the word. As the ground sinks, it alters how the house sits by causing the foundations to shift and stretch. This causes damage and cracks to walls, ceilings and floors within the home. If it gets serious enough, it could even structurally compromise the building.

What causes subsidence?

It can be caused by one (or more) of several things, including:

Clay shrinkage
In warmer weather, clay-rich soil beneath a property sees the water it stores evaporate off. As this happens, it shrinks, meaning the ground above it drops slightly. For example, the UK heatwave in the summer of 2018 saw an increase in subsidence claims due to the dry weather and heatwave.

Tree roots
Trees can cause subsidence in one of two ways. Firstly, they draw water from the soil to grow. The removal of water causes the soil to shrink. Secondly, as the roots burrow down and out, they can change the soil density, structure and compactness, causing the building foundations to shift.

Too much water movement
If there’s too much water movement, it washes away the soil, leading to subsidence. This washing away could be caused by leaking or blocked drains, flooding, heavy rainfall or escaping water. The ground eventually becomes less stable.

Poorly built foundations
Older buildings tend to have shallower foundations constructed with fewer guidelines and measures in mind. As such, they can shift. In newer houses, using the wrong materials or not properly preparing the site could also lead to subsidence.

How to spot subsidence

Look out for the following signs, all of which could indicate a subsidence problem.

Cracks in interior walls – usually, these are harmless. However, when a building subsides, all the walls start to move, with stress points changing as it shifts position. This can lead to obvious cracks. If cracks continue to widen to more than 15mm, it could mean an ongoing subsidence issue. It’s essential to not simply ignore the problem and plaster them over every time.

Cracks in exterior walls – in the same way as above, exterior walls shift. You might notice cracking in the mortar or bricks as you look at the house from outside.
Wallpaper ripples – this problem is usually caused by humidity. Check the room’s humidity level by seeing if there is condensation on the window in the mornings. If there isn’t, the ripple could be due to the walls moving because of subsidence.

Windows and doors not fitting – if windows and doors suddenly become tighter or won’t open or close altogether, it could be because of subsidence. As the structure moves, the fine space between the walls and the windows and doors alters. You might also notice plaster cracking or wallpaper ripples around the door or window.

Why subsidence is dangerous

Subsidence is dangerous because it can compromise the structural strength of a house. If it’s left unaddressed for years, it could eventually lead to the house collapsing. Any house with a known subsidence issue will be much more challenging to sell or insure, meaning you might be stuck there for a while. Finally, if a house is currently experiencing subsidence, it makes it much harder to get a mortgage, meaning the only way to buy the house would be through a cash sale. As always, the cost of prevention is much lower than the cost of repair.

Can a home survey check for subsidence?

Home surveys, carried out by expert chartered surveyors, check for subsidence and, if it’s present, they will find it. All the details will be recorded and set out in the home survey report, which will then be available for you to read. Crucially, the surveyor will also recommend what you do next. Subsidence can usually be fixed, but not always. For example, trees can be removed, water problems can be addressed, and, in extreme cases, the entire property could be underpinned. Overall, we’d usually suggest avoiding buying a house with a history of subsidence unless you’re prepared to accept the risks that come with it. That being said, everything is always addressed on a case-by-case basis.

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