Spotting Subsidence and Taking the Appropriate Action

Spotting Subsidence and Taking the Appropriate Action

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The downward movement of the ground beneath a building is called subsidence. It is potentially caused by a number of different factors, though some are more common than others, all are potentially very damaging to a property and could be costly to repair. Swift action and investigation is always the best way to deal with suspected subsidence, as if you are able to identify a cause you might be able to take preventative measures before any disruptive underpinning works need be considered. There are a number of indicators of subsidence to watch for, and though some may also be caused by the natural movement of a building over time, it is important to seek professional advice where ever there is cause for uncertainty.

Homes built on clay soils are particularly susceptible to subsidence issues, as clays hold a significant amount of moisture which will cause shrinkage if removed. Moisture can be lost during extended periods of warm/dry weather, not only by way of natural soil dehydration but also through extraction by nearby trees looking to slake their thirst. Soils that are rich in peat or other organic matter might encounter similar difficulties as the organic matter decomposes quicker as the soil dries out. Soils with high concentrations of sand or gravel is likely to be washed away if drainage systems beneath a property begin to leak. Buildings that sit on slopes may be at risk of landslip, where the earth beneath becomes unstable over time and begins to slide downhill.

Areas with a history of mining activity may indicate the presence of underground mine shafts. Abandoned shafts may sit unnoticed beneath a home for decades without ever causing a problem, but when they do it is likely to be catastrophic. The main danger is that mine works that were closed over a hundred and fifty years ago may not have been properly documented, so may not show up on a mining check. The pit props that hold up old shafts are likely to be little more than timber frames, so over time they can deteriorate until eventually they are no longer strong enough to hold up the immense weight of the earth above. The extent of damage this may cause will depend on how far away the mine shafts are from your property and how deep they run, though even mines some distance away can cause severe subsidence.

Cracks may appear in your walls from time to time, often these will be attributable to atmospheric factors and can be repaired with filler and painted over, but you should contact your insurer immediately if you ever feel unsure. Subsidence cracks are usually noticeable by being tapered, diagonal and visible from both the inside and outside of the property. They will often spread from frames around doors and windows, and doors/windows may stick when opening/closing. If cracks open wider than 3mm (1/8”) then you should consult your insurer immediately. You should also be aware of wallpaper rippling as this may indicate the presence of cracks underneath.

Once noticed you will probably not be able to implement remedial works straight away, as subsidence signs may need to be monitored while investigative measures are undertaken to establish cause. This can include drain inspections and surveyor consultation. Even if leaking pipes and drains are not the cause, they are likely to occur as a result of ground movement. Once the cause has been isolated, you will be able to take steps to rectify the problem. Removal of a tree may be necessary, though this should always be done under advisement of a qualified arboroculturist. If not attended to properly, tree removal could lead to heave (the opposite of subsidence, where the ground moves in an upward direction but can be equally destructive) and improper pruning could encourage further growth.

Underpinning or piling (or mini-piling) can be immensely expensive and severely disruptive, so should always be treated as last-ditch options. Most standard home buildings insurance policies will provide cover for subsidence, heave and landslips; however, if a property has suffered from any of these in the past or is in an area prone to any of these, they may be excluded from the policy. In this case, you will probably need to have subsidence insurance cover to help you meet the cost. Most policies will require you to pay around £1,000 excess for a subsidence claim – but when you consider that underpinning can cost between £5,000 and £50,000 – a grand is a small price to pay. Once subsidence has been put right, you can begin repairing the other more cosmetic types of damage. This may involve rebuilding brickwork or redecorating interior walls.

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Categories: Exterior Home

About Author

Krayton M Davis

Executive Manager: LetsRenovate Team