What is the shrink-swell problem? 

Shrink-swell is a term describing the natural behaviour of clay-rich soils. When it rains, clay absorbs significant amounts of moisture, causing it to expand and when it dries out it contracts. Repeated shrinkage and swelling can cause differential ground movement beneath foundations. During extended dry periods the ground may contract and settle, while rewetting can cause heave or recovery movement. Amid prolonged drought conditions, the shrinking phase can become severe enough to cause structural movement.   

Climate change is amplifying the problem. Heatwaves are becoming more common and hotter, drier summers are drawing even more moisture out of the ground over longer periods of time. The emerging patterns presented in the BGS data suggest that this trend will intensify. That means areas which may have only experienced minor or occasional shrink-swell activity may now face it as a recurring challenge. Homeowners already in high-risk areas, the problem is even more severe. 

Is your property at risk? 

Not all homes are at risk of subsidence. The more susceptible properties are sitting on clay-rich soils and made-ground.  

Clay soils are dominant across the UK, especially in London and the south-east and East Anglia, and the Midlands, so there is potential risk of significant ground movement. 

Properties built on ‘made-ground’ such as former industrial land or backfilled ground, can behave unpredictably under moisture stress. That’s because the material used to fill the ground may not be uniformly compacted. This increases the risk of differential settlement, which is often difficult to identify from the surface.  

So, what are the early signs of subsidence? Some indicators homeowners should watch out for include: 

• Diagonal cracking, especially at the corners or windows and door openings.

• Doors and windows that suddenly stick or become misaligned.

• Gaps appearing between skirting boards and floors.

• Visible movement in garden walls.

It’s worth noting that while these are some of the most common signs of subsidence, visual indictors alone are not enough for a diagnosis.  

Why visual signs are only half the story 

A crack in a wall could indicate several things. Fine or hairline cracks may be a sign of your house naturally settling or normal seasonal temperatures. Larger, wider cracks can could suggest ongoing and progressive movement. Without a full understanding of what is happening beneath the surface, it’s not possible to accurately assess the severity of the issue or identify the best course of action. 

A general builder or a standard structural surveyor may not be equipped to make the best decision, and making any remediation works without a proper understanding of the subsurface can be counterproductive and costly. To thoroughly investigate the ground conditions beneath the surface, contacting a ground engineering specialist, such as Mainmark, is your best call. 

What do ground investigations involve? 

A professional ground investigation is considerably different from a visual inspection, or building survey. It typically starts with a review of your property’s history and geological records and is followed by a site survey, which may include taking soil samples to understand how the subsurface is behaving. Vegetation and drainage are also assessed as moisture levels have a significant impact on how soil behaves. Once everything has been analysed, the geotechnical engineer will have a full picture of what’s happening and the appropriate remediation strategy can be designed.   

Geotechnical engineering solutions work by address the root cause of the issue, rather that just treating the symptoms. Traditionally, subsidence repair involved mass concrete underpinning, where sections of the ground is excavated and filled with concrete, however, it can be a long and costly process.  

Modern techniques such as expanding resin injection, works by injecting material directly into the ground beneath foundations, filling voids, densifying loose soils, and restoring load-bearing capacity with minimal disruption to the property above. 

Getting help from the experts 

The key takeaway from the BGS report is that the shrink-swell problem is not going to disappear. For homeowners who live in the more vulnerable clay-rich soil or made-ground areas, it’s all about how well-understood and well-managed the risk of subsidence is. 

With extensive experience across UK, Mainmark has the knowledge and expertise to address shrink-swell subsidence properly, from root-cause diagnosis through to targeted remediation. It all starts with a thorough understanding of the ground. 

If your home is showing signs of subsidence, or you are in a high-risk area and want to understand your exposure before problems develop, getting a professional assessment is your first best step. Contact Mainmark today for a site visit.