Homeowners in the United Kingdom are at risk of significant financial loss as experts predict a subsidence "super-event" driven by prolonged dry weather and heatwaves. An unprecedented number of subsidence claims are anticipated, potentially reducing property values by as much as 25%, according to Money Mail.
Millions of homes could begin to show large cracks in the coming months as the soil beneath them dries out and shrinks. This phenomenon is particularly concerning for properties built on clay soil, which expands when wet and shrinks significantly when dry. Andrew McColl, chairman of the Residential Property Surveyors Association, explained that the back-to-back extremes of wet winters and dry summers in many parts of southern England have created a perfect storm for ground movement.
"In a wet winter it swells, and in a hot dry summer it shrinks, and a house sitting on it can move as the ground moves," McColl stated. "What makes this year unusual is that many parts of southern England have had both extremes back to back. In those areas the ground has swollen and then shrunk further and faster than normal, and that is exactly the recipe for movement."
Insurers are preparing for a substantial increase in claims. Aviva boss Amanda Blanc has already indicated that the insurer will need to increase its reserves to cover the expected surge. The Association of British Insurers (ABI) reported a record £307 million paid out for subsidence claims last year. This year is shaping up to be a "super event year," according to Michael Lawson, chief executive of subsidence adviser Property Risk Inspection, with soil moisture conditions similar to those seen in previous high-claim years. The industry is facing a "double tap" of high claims, a situation not seen since 1990-91.
The strain on repair services is already evident, with professionals booked up due to claims from the previous year's dry summer, leading to potential delays in addressing new issues.
Properties most at risk are those situated on clay soil, common in large areas of London, the South East, and East of England, as well as other regions. Victorian and Edwardian homes with shallower foundations are also more vulnerable. Extensions and conservatories, with their typically shallower foundations, are particularly susceptible to movement. Additionally, trees planted near homes on clay-rich soil can exacerbate the problem, as their roots absorb water, causing the soil to shrink further. Large, older trees such as oak, poplar, elm, horse chestnut, and willow are of particular concern.
Homeowners should watch for signs such as stiffening windows and doors, diagonal "step-like" cracks, especially near bay windows or corners of the house, and wrinkled or torn wallpaper. Cracks are typically at least the width of a pound coin and may appear both inside and outside the home. Hairline cracks of two millimeters or less are generally not indicative of subsidence.
Most standard home insurance policies include cover for subsidence, though a higher excess may apply. If subsidence is confirmed, the diagnostic process alone can take six months, and repairs may require a further six months for a certification of structural adequacy to be issued, which is essential for selling the property without a significant loss in value. Repair costs can range from thousands to over £100,000 in severe cases, with solutions like underpinning or resin injections employed. In many instances, addressing the underlying issue, such as removing problematic trees, can resolve the problem, but professional advice from insurers, tree surgeons, and structural engineers is crucial before taking action.