What is subsidence in a property? 

Subsidence occurs when the ground beneath a property’s foundations sinks downwards, causing the structure above to sink or shift unevenly. Typical signs of subsidence include diagonal cracks in walls, doors and windows that suddenly stick or become misaligned, or uneven or sloping floors. 

What causes subsidence? 

Subsidence can be caused by several factors: 

• Clay soil shrinkage: Clay-rich soils expand when wet and contract when dry. This movement can cause an uneven shift beneath the foundations.

• Trees and vegetation: Large trees or shrubs close to a property draw significant amounts of moisture from the surrounding soil, which can cause it to shrink further.

• Leaking pipes or damaged drains: Any escaping water can over saturate the subsoil, washing it away or weakening the supporting soil.

• Ageing properties: Older properties with shallow foundations are more prone to movement because they sit within the top layer of soil. This is where moisture levels fluctuate due to weather and vegetation.

How much does subsidence devalue a property? 

The short answer is it depends. Many estate agents or chartered surveyors will quote 20% but this is just an average. In reality, the impact on value depends on the property’s actual circumstances.  

Typical percentage drop in value 

The typical percentage range is based on the status of the subsidence.  

It’s important to remember that these are just starting points for understanding where a property might sit, they’re not guarantees. 

Factors that affect how much value is lost 

So, what determines the exact figure?  

• Severity of subsidence: Minor historic cracking has a significantly different impact compared to ongoing, unresolved subsidence.

• Ongoing vs historic movement: Properties that have been fixed, hold official documentation of repairs and experience no further movement, typically hold their value far better than those with active subsidence.

• Certification of any repair work: Buyers and lenders will want to see a completion certificate and a structural engineer's report confirming the work meets the latest building regulations.

• Caution in the market: Some mortgage lenders are cautious about properties with any subsidence history. This can narrow down the amount of potential buyers to cash purchasers in more serious cases.

• Insurance history: It’s also worth noting that subsidence claims are recorded on the Claims and Underwriting Exchange (CUE) database. That means the claim becomes a part of the property’s history, even after it’s been repaired.

How does underpinning affect house value? 

Underpinning is a method of subsidence repair that strengthens a property’s foundations. If works are completed properly and signed off by a structural engineer, it can significantly reduce the loss in value compared with unresolved subsidence. 

However, it’s worth remembering that even if a property has been fully repaired and carries official documentation of underpinning, it may still be discounted. That’s because some lenders remain cautious due to the risks associated with future movement, which can lead to a loss in value for the property. However, if you can get home insurance coverage for subsidence, and the works carried out are warrantied, then this normally appeases them  

Traditional concrete underpinning has been a popular method for fixing subsidence repair, but it's often disruptive and takes several weeks to complete. Modern repair techniques such as resin injection and computer-controlled grouting can often be completed in a day, with minimal disruption to the property or its occupants. These non-invasive modern methods can mean less disruption to daily life, and the property can be put on the market faster.   

Can you sell a house with subsidence?  

Yes, you can still sell a house with subsidence, but what really matters is that you’re fully transparent. Buyers, mortgage lenders and surveyors will also want to see appropriate documentation such as: 

• A report from a structural engineer to confirm the current condition of the property.

• A completion certificate for any repair work carried out.

• Evidence that repairs meet recognised building standards.

Transparency typically results in a smoother sale process. 

How Mainmark Ground Engineering can help 

Identifying subsidence early and getting it repaired with the right method can help reduce the devaluing of your property, allowing you to move on confidently if you’re planning to sell or stay in your home.  

If you have concerns about subsidence or are looking at repair works before a sale, a home survey can make a big difference. Mainmark can visit your property and assess the ground conditions, identify the root cause and severity of the issue and recommend the appropriate remediation works. Our non-invasive methods can help protect the structural integrity and value of your property. To find out more, contact us today.