What is subsidence and what causes subsidence?

Defining what subsidence is helps you understand why it can be a real headache for building owners. Whether that’s a commercial property, a residential property (new build or existing), or something more specialist such as sea ports, airports and so on.  You need to know your building is set on strong foundations and want to be secure in the fact that the structure will withstand the weather, soil conditions and any geological changes for years to come.

The definition of subsidence can be summarised into the following: subsidence refers to the downward movement of soil mass underneath foundations resulting in the structure above, gradually or suddenly, sinking into the ground. It is often seen as being a relatively infrequent issue affecting the built environment, however, when subsidence affects a property or infrastructure, it can be a costly and time-consuming task to find a suitable solution.

Causes of subsidence include, but aren’t limited to:

• Soil types under your building – typically clay soils
• Tree roots – affecting moisture levels
• Leaking drains or pipes – saturating ground
• Poor ground or soil compaction – poorly prepared foundations
• Drought or long dry periods, which can cause clay to shrink and crack
• Shallow foundations or inadequate building foundations

We’ll be covering these causes in more detail in the near future as each cause has its own correction, which Mainmark has built a reputation on solving.

It starts with understanding what subsidence is, so you know what signs to watch for in your property before problems worsen. While you can’t always control ground conditions, there are steps to reduce the risk of subsidence—especially with clay soils or older infrastructure.

Start with proper site investigations – if you’re a developer, a homeowner or a home buyer – know your soil type. Checking for drainage and nearby vegetation helps inform design decisions.

For existing buildings, keep drains in good condition—leaks can erode soil. Be cautious of large trees like oak or willow; their roots dry out clay, causing shrinkage.

In new builds, ensure ground is well-compacted. Where needed, technologies like geopolymer injection can add strength.

If you’re a homeowner or a building owner, the first step is to confirm that subsidence is the cause of any cracks or movement in your property. A structural engineer or surveyor can assess the situation and advise on next steps. If the issue is confirmed, your home insurance provider may help cover investigation and repair cost – this can be the most cost-effective way of fixing subsidence issue.

Traditional underpinning methods can be effective but often disruptive and expensive. Many homeowners now opt for modern alternatives like resin or geopolymer injection—quicker, cleaner solutions that stabilise ground with minimal disruption, such as the services offered by Mainmark.

Whatever the solution, early action is key. The sooner subsidence is addressed, the less damage it’s likely to cause.

If you suspect subsidence, it’s important not to ignore it. Start by getting a professional assessment from a qualified surveyor or structural engineer to confirm the cause.

If subsidence is diagnosed, contact your home insurer to check your cover and next steps. Keep records and photos of any visible damage.

In many cases, modern methods like Teretek® resin injections can resolve the issue quickly, meaning subsidence can be handled quickly, at a reasonable cost and with minimal disruption.

Importantly, speak to the experts. Get a free, no-obligation quote from Mainmark today and find out how we can help stabilise your property.