Reducing the impact of subsidence through early detection

Working in the insurance industry we can talk about subsidence at length, but this knowledge is not shared by the vast majority of homeowners who understandably remain unaware as to what’s happening beneath their feet.

The combination of extreme warm and dry weather is, excuse the pun, a perfect storm for subsidence. Deemed a climate-related risk, subsidence claims are expected to become more commonplace.

Repairing a home that has subsided can involve major works and considerable disruption for the residents. Like many things in life, the sooner the issue is spotted the easier it may be to fix, so when is it subsidence and when is it just a normal crack?

What is subsidence?

Subsidence is the vertical downward movement of building foundations caused by loss of support of the site beneath the foundations. This is usually associated with a change in the sub-soil volume, such as clay shrinkage. Trees can extract moisture from a clay sub-soil during a dry/warm summer, often following a dry winter or spring, which results in the desiccation of the soil and causes the clay to shrink. This then allows the foundations to settle, often causing cracking in walls.

As well as trees extracting moisture, the cause can be more temporary such as a water erosion. In almost the reverse, a leaking pipe or drain will impact the integrity of sub-soil under a property by saturating the ground.

Other less frequent and unnatural causes include poor foundations such as unstable ground or nearby construction producing vibrations.

Has this happened in the UK before?

The last big subsidence event was in 2022, and this was picked up early as sometimes it gets noticed when properties are valued to sell. As the housing market is currently slow with fewer sales than in 2022, home buyer’s surveys are not picking up the early indicators of subsidence meaning that the damage is likely to more significant before it is noticed.

While there has been recent speculation that climate change could lead to a rise in subsidence, I think it is important to remember that for clay-shrinkage subsidence to occur, specific conditions are generally required to trigger a subsidence ‘event’; usually a dry winter/spring followed by a prolonged dry and hot summer.

The response

The industry’s capability to manage technical subsidence claims in the field is not what it once was. While comparatively the frequency is low and the knowledge is niche, it requires expertise, and it is becoming apparent that expertise requires more resource.

To accommodate this skills gap, I believe as insurers we can diversify and build on our existing skillsets. Upskilling initiatives such as internal apprenticeships not only enable us to support individual career progression but they allow us to grow our expertise from the inside out.

We're already talking about how we can leverage technology to support our identification and prevention of subsidence, and I look forward to seeing how this develops and how we can better help our customers.

Prevention is the goal, and there is a collective agreement within the insurance industry and amongst expert suppliers that we must increase education and awareness amongst homeowners of both the causes and symptoms of subsidence.

Being aware of the typical indicators is invaluable, so we hope by sharing information we can increase the chances of early detection for all homeowners.

What to look out for

It is important to remember that cracking in buildings can occur for a number of reasons and not all cracking and damage is related to subsidence or foundational movement.

Buildings of all ages and construction type incur changes in both temperature and moisture levels throughout a typical year, as well as minor seasonal movements vertically and laterally.

Subsidence cracking is specific in its nature and pattern, and is the result of downward movement of the ground in dry summer seasons and upward movement in the wetter winter months.

Typical signs of subsidence 

• A vertical diagonal and tapered crack in plasterwork or external masonry, notable wider at the top that the bottom
• Typically this cracking occurs around window and door openings and in the areas where trees or vegetation may be closest
• Normally the cracking is mirrored both internally and externally
• Windows and doors appear to become difficult to open and close, with gaps forming at the corners of architrave frames
• Vertical separation of connecting structures such as extensions and conservatories, with the appearance of the separation being wider at the top than the bottom
• Appearance of floors sloping and separation between the skirting boards and floor surface
• Rippling or rutting of paper on walls in corners or around window and door openings

Signs unlikely to indicate subsidence

• Most horizontal cracking
• Minor hairline spider web cracks in a random pattern, this is most likely de-bonded plaster or render
• Cracking within brickwork above windows forming a pyramid style pattern, typically due to lack or absence of support above a window or lintel failure
• Cracks that are even and consistent in width and not diagonal, most likely shrinkage and thermal, commonly found between joining plasterboards
• Cracking to UPVC or timber door frames at the junction where they are fixed to walls, likely due to long term use of the door or shrinkage of sealants
• Damp on internal walls, this is not caused by subsidence

While not all cases of subsidence can be prevented, managing nearby trees and shrubs and maintaining gutters and pipes to prevent leaks can reduce your customer's risk. Typically, a tree that is closer in distance to a property than its height (e.g. a 10m tree only 5m from a property), could potentially cause subsidence on a clay sub-soil.

If your customers think their property has experienced damage from subsidence, encourage them to contact their insurer as soon as they can.