It goes without saying that buying a home is likely to be the biggest single investment you make in your lifetime and therefore, it is important to understand issues that may be affecting the structure now, or at some time in the future.
Subsidence refers to the sinking or settling of the sub-strata (ground) due to a combination of natural and/or human-induced activity. The process of subsidence can often occur gradually over time (over a number of years and even decades) or very suddenly, depending on the cause.
Impacts of subsidence on built and natural environment
Subsidence can have a significant impact on the built and natural environment, as well as the safety of building occupiers/visitors. Depending on the severity of the movement, subsidence can render most domestic properties un-inhabitable until full repairs are undertaken.
One of the most common causes of subsidence is the withdrawal of sub-surface moisture, such as groundwater, oil, and/or natural gas. When these fluids are removed from the ground at a faster rate than they can be replenished, the soil and rock above them can often collapse, resulting in subsidence. This is known as “compaction subsidence” and is a major problem in areas with heavy groundwater use or fluctuating water tables.
Another cause of subsidence is the collapse of underground mines and tunnels. As these structures are excavated, the ground above them can often settle and move, resulting in subsidence. This can be a significant problem when purchasing a property located on old coal fields, or close to open mines.
Climate change can also play a significant role in subsidence. Although further investigation and research in this particular area of study are necessary, it is a commonly agreed consensus that sea level rises caused by the melting of glaciers and ice sheets, as well as the thermal expansion of seawater, can lead to subsidence along coastlines.
Additionally, changes in precipitation (rainfall) patterns and the frequency and intensity of droughts can affect subsidence through changes in soil moisture and the rate of soil erosion. This is particularly common in sandy and clay-based soils.
Managing subsidence risks: tips for home buyers
Subsidence can have significant impacts on the built environment, including damage to buildings, roads, and other infrastructure. In addition, subsidence can lead to flooding and an increased risk of storm damage. The loss of wetlands and other natural habitats can also occur as a result of subsidence.
When purchasing a property in an area at a potential risk of subsidence, it is important to have a survey undertaken in order to assess the condition of the building fabric and understand any potential risks moving forward.
A thorough survey (such as a Level 3 Building Survey) should be able to identify any signs of active or present subsidence and any searches undertaken by the Chartered Surveyor should identify any potential risk going forward (such as buying a house on a known coalfield).
There are a number of insurance policies that cover the threat of subsidence once a property is purchased. Your Legal Adviser should undertake all relevant searches in this regard and advise you accordingly.
Overall, subsidence is a complex problem that can have significant impacts on the built and natural environment, as well as on human health and safety. However, through the use of effective management strategies, the effects of subsidence can be minimized and prevented.
