Subsidence: What is it and how to prevent it

When we think of issues in and around the home, the first few examples that may come to mind, might be roof damage, a leaky pipe, damp and mildew, or even the out-of-date décor. Subsidence however, is not necessarily an issue that instantly springs to mind. For property owners or potential buyers, subsidence is a very real and serious concern, that can cause major problems if not prevented or managed.

What is subsidence?

Subsidence is caused when the ground underneath a building begins to collapse or sinks lower, effecting or taking with it, the buildings foundations. Clay soil is very susceptible to subsidence, especially during the warmer months when the earth shrinks due to extreme dryness. Trees can also contribute to subsidence, with species such as Populus, Oak and Conifers having a higher water intake than other trees, therefore absorbing large amounts of moisture from the soil.

Noticeable signs of subsidence can include large, thick cracks that often appear next to a door or window and can often spread internally and externally. Other signs may include shrinkage in wallpaper, jarring of windows and doors, and cracks running along the masonry. Fixing subsidence can be extremely costly and invasive so if you feel that your home is showing signs of subsidence, contact your insurance provider right away, to see what exactly you will be covered for.

While cracked brickwork, and doors or windows jamming, are a common sign of subsidence, it could also mean that your property is suffering from ground heave. Ground heave has the opposite effect of subsidence, as the ground will tend to heave upwards when soils (particularly clay soils) expand due to excess moisture.

The damage caused by ground heave can be just as detrimental to your property as subsidence but will require a different approach to managing it.

Buying a property with subsidence

When going through the process of buying a property, it is important to ask your solicitor and the surveyor questions such as “Has the property ever experienced subsidence” or “Is the property prone to developing subsidence?”. Your solicitor should be able to provide you with a detailed history of the property which should highlight if the property has experienced subsidence in the past. A detailed inspection by a reputable surveyor, should also highlight if the property is currently experiencing problems directly related to subsidence. In most cases, solicitors and surveyors are legally obliged to inform you if the property has experienced subsidence, however it is always a good idea to request this information and check the details thoroughly.

By obtaining this crucial information upfront before purchasing a property, buyers are in a much better position if they wish to proceed with the sale. If a property has experienced subsidence in the past or currently has subsidence, it does not mean the property is unfit for purchase. It does however mean that additional precautions need to be undertaken.

How to prevent and manage subsidence

If you feel as though your property could be prone to subsidence, there are measures that you can take to help prevent long term damage.

• If you are thinking of planting trees on your property, make sure to check what type of root system the trees have. If you are planting trees with a deep root system, plant them at least 40 metres away from your property, to help prevent the roots from invading your foundations and sucking out the moisture from the soil. Trees may include Maples, Oaks and Populus.
• If you have well established shrubs planted close to the foundations of your property, do not be tempted to dig them out right away. By disrupting the established root systems of the shrubs, it could cause the soil to become unstable or for water to build-up. Either regularly prune the shrubs to help reduce their water intake or speak to a specialist tree surgeon/gardener who can advise on the safest way on removing the shrubs.
• If you are planning on adding an extension onto your property, be sure that all work is carried out by reputable professionals, as poor foundations could cause the extension to sink lower than the original structure.
• Make sure all external drainage is well maintained, by regularly cleaning the gutters, and making sure nothing can potentially block the down pipes and drains. If water is unable to freely drain away, the backlog of water could cause the soil to soften and move.
• Other factors can determine if your property is prone to developing subsidence, such as location and soil type. Properties located near an active, or old and disused mine could experience weakened or unsettled soil. Clay soil will absorb moister and therefore expand, but then contract when dry. Such movement of the soil can leave voids where the expanded soil once was. Soils with a high sand or gravel content are prone to being washed away by excess water, which can therefore weaken foundations.

Unfortunately, there is no easy fix for a property that is experiencing subsidence. If you suspect that you have subsidence, you should seek advice from a professional who can give you a more accurate diagnosis. Once it has been confirmed by a professional that you do have subsidence, your foundations may need strengthening. A common method to help strengthen foundations is known as underpinning. Underpinning will need to be undertaken by professionals, and not surprisingly the process can be costly and time consuming and could affect your insurance premiums moving forward.

It is important to note that not all insurance providers will cover subsidence as standard and may charge extra for this type of cover. At Guardcover Unoccupied Property, we can offer protection against unforeseen events such as subsidence.