What is subsidence?

‘Subsidence’ is when a piece of land begins to sink. As you can probably imagine, this can present a very serious danger to any properties built on the land; try to imagine ground movement that causes parts of your property to pull away from each other and you will have a basic idea of the dangers involved.

When subsidence causes a major problem it can be hugely expensive to fix, to the extent that most home insurance policies cover subsidence as standard. It can also make or break a property sale, as a homebuyer must have been informed about any previous issues with subsidence when making an offer on a property.

In short, subsidence can be a huge problem for a property! It pays to keep a close eye out for signs of subsidence so that any issues can be identified and fixed before they become a disaster. 


What is a subsidence survey?

A ‘subsidence survey’ is a careful inspection of a property to see if it is suffering from subsidence and, if so, whether it will continue to make the building deteriorate. It will be handled by a qualified structural engineer, who will pinpoint any damage and inform you about any necessary corrective work.

At first, your engineer will perform a standard visual inspection, where they will look for signs in your walls, ceiling and flooring. They may also need to perform an ‘intrusive inspection’, where they will also examine hidden structural elements.

Depending on the extent and cause of your problem, other Pros may also need to be brought in for your inspection. For example, a tree surgeon could be called in to examine how plant life is impacting your property and whether it needs to be removed. Similarly, a drainage specialist could be asked to pinpoint drainage defects which are causing leaks and subsidence.

After the survey, your Pro may offer a quote for the corrective work outlined in their findings. You should not feel any pressure to accept the offer immediately, especially if the danger is still in an early stage, so try to take the time to collect more quotes if you can. Having said that, you should still make the repairs a priority. If the subsidence get worse, your issue will only become more expensive to repair.

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Signs of subsidence

Luckily, it can be fairly simple to identify signs of subsidence in a property:

  • Have you spotted new cracks in your wall? New vertical or diagonal cracks that are wider than 3mm can be a sign of subsidence, especially if you see that they are widest at the top
  • Have cracks been appearing about openings in your walls, such as windows and doors? Subsidence can also cause frames to warp, so you might notice that your windows and doors have been sticking
  • Has your wallpaper been crinkling around the wall and ceiling joints?
  • Do you have cracks in your property that seem to open and close seasonally?

If you have seen any of these signs around your property then it can be a good idea to hire a structural engineer to perform a subsidence inspection right away.


Am I at risk from subsidence?

Certain signs of subsidence can actually be caused by other issues. For example, your doors could be sticking because the lintels above them have worn down and need to be replaced, or cracks in your walls may have been caused by thermal movement instead of subsidence.

You may be at more or less of a risk from subsidence depending on the type and location of your property:

  • Properties built before 1976 will typically have shallower foundations, which can put them at higher risk from subsidence
  • Does your property have any particularly large shrubs or trees? These can suck moisture out of the soil, making it dry and more vulnerable to subsidence
  • Leaking drains and water mains can soften the soil under a property, which in turn can make it collapse under the weight of the building on top
  • A drought-prone area where the soil regularly dries out will be vulnerable to regular subsidence
  • Soils with a high clay content are particularly prone to drying out in hot weather
  • Areas with local mining can experience regular subsidence. The fill material used in closed quarries or pits can also decompose over time, leading to ground movement 

One of the first things to do if you believe that your property is showing signs of subsidence is to check to see if it is common in your area. Take photos of the signs that you notice and speak to a local structural engineer as soon as possible. You should also check your home insurance policy to see if you are covered against subsidence; if not, you could have a very expensive repair job on your hands!