As most will remember, 2018 saw an uncharacteristic six week long heatwave. This hot spell led to a surge in subsidence claims from both homeowners and building owners. The Association of British Insurers (ABI) said the ‘357% increase in the value of claims was the highest quarterly jump since records started more than 25 years ago.’
The heatwave conditions affected many building foundations as sustained warm weather caused water from subsoils to dry out, resulting in shrinkage. When this shrinkage occurs the ground can no longer support the building, the foundations gradually move downwards, causing the property to sink in one area or across the entire foundation footprint; this is subsidence. Cracks in walls, sinking or sloping floors, or windows and doors becoming jammed are the common indicators that a building has subsided. Problematic wall cracks will typically start at windows, doorways or corners of buildings and if they are larger than 5mm then professional advice should be sought.
It is the building owner’s and employer’s responsibility to ensure a safe working environment. Subsidence causes a range of safety and health risks including uneven floors, especially dangerous where machinery is in use, drafts and dampness. In the event that 2019 proves to be another dry summer, business owners and FM managers should fix any outstanding subsidence issues their building is experiencing. To help ensure it doesn’t worsen, it’s recommended that a thorough check of the property is conducted, looking for signs of issues, effectively carrying out a ‘spring clean’. There are some key considerations to keep in mind:
Drainage, Pipes and Guttering
Poor drainage systems and leaky pipes can cause varying moisture levels in some clay soils which can shrink, or crack and shift during hot weather, and then expand during wetter seasons. In fact, a consistent flow of water leaking into the soil can saturate the ground and even wash away part of the foundations. These issues can prove expensive if they’re not taken care of. Proper maintenance is essential; make sure drains are free-flowing and ensure guttering doesn’t become clogged-up, leak, or overflow.
Tree Roots and Shrubs
Trees and shrubs need large amounts of water to survive. A mature deciduous tree, for example, requires thousands of litres a year. If they are in close proximity to a building they can cause damage to the foundations, meaning ground remediation work may need to be undertaken. If there is a tree close to the property in question, the owner should make sure it is managed and maintained to ensure it does not become a problem. Don’t plant trees too close to a building, garage or outbuildings. The ABI suggests willow trees need to be no closer than 40m from the nearest building, poplars 35m away, and oaks and elms 30m away. For those unsure whether a tree could be causing damage, seek professional advice.
Ground engineering experts Mainmark urge those responsible for buildings to look for the warning signs, act now, get ahead of the game and reduce the risk of subsidence this summer. By ensuring the above are addressed, a building’s risk of subsidence this summer can be greatly reduced.
Should a property subside, it is important to know that there are more advanced solutions available besides traditional concrete underpinning.