After a summer of record-breaking temperatures and repeated heatwaves, many UK homeowners are noticing cracks appearing in walls, ceilings, floors and brickwork. The phenomenon has been especially prevalent in London and in older Victorian and Edwardian properties.
Numerous Britons have shared photos on Reddit of cracks in varying lengths and sizes along the tops of walls, ceilings, floors and around windows, with some also spotting exterior cracks in brickwork. While some residents are unconcerned, others have been left 'panicking' and feeling 'scared' and 'unsafe', unsure if the cracks signal a more serious problem such as subsidence.
What is subsidence?
The Royal Institution of Chartered Surveyors (RICS) defines subsidence as the 'downward movement of the foundations of a building due to changes in the supporting strata'. Heatwaves can cause this because some houses are built on 'shrinkable soil' such as clay. During periods of high heat, the moisture is lost from the soil, the clay shrinks, and the foundations drop, potentially causing structural damage.
'Different types of clay shrink and swell at different rates,' RICS adds. Subsidence can also be caused by trees near homes, as their roots can absorb moisture from the soil and cause it to shrink. As well as causing structural damage, subsidence can devalue a property by as much as 20 to 25 per cent.
How to tell if cracks are serious
In most cases, the first signs of subsidence are visible cracks in one area of the house. However, RICS experts claim there is 'rarely any cause for real concern' unless cracks appear suddenly and are more than 3mm wide (thicker than a 10p coin). Buildings naturally move over time, and materials respond to changes in temperature and moisture, so some cracks can be purely cosmetic.
Homeowners should monitor and measure any cracks in plasterwork or brickwork for at least 12 months to see if they are expanding. Other potential signs of subsidence include new or expanding cracks in outside brickwork, doors and windows sticking for no apparent reason, ripping wallpaper, and new sloping or dipping of solid ground floors. If these issues appear without a clear cause, specialist help should be sought as soon as possible, as fixing subsidence can take years.
Why London is particularly affected
Those in the Southeast of England have reportedly been facing historic levels of subsidence after five heatwaves during the summer. London is particularly impacted because about 80 per cent of the city sits on clay, and Victorian and Edwardian homes are most at risk as they were built directly onto the upper layers of clay.
Insurance claims linked to subsidence hit a record number last quarter, according to data from the Association of British Insurers (ABI), with households claiming on average £20,000. Laura Hughes, head of general insurance at the ABI, told The Telegraph: 'We expect to see more subsidence cases because of the hot weather.' Otso Lahtinen, chief executive of Geobear, a ground engineering specialist company, told Bloomberg: 'It's crazy, what's happening now. It's the new norm, and it seems it will happen more often in the next 20-30 years.'
What to do if you suspect subsidence
If concerned, homeowners should keep an eye on cracks, measure them and take photos. They should also contact their home insurer as soon as possible, who will help arrange for a structural surveyor to assess the property. Cracks should not be filled in or redecorated before the property has been examined by a professional.
If subsidence is confirmed, it can often be rectified, but this can take up to two years. Experts will help stop the movement and stabilise the foundations of the property. Depending on the severity of the structural damage, the methods and cost of stabilising can vary greatly.
