What is Property Subsidence?

08/01/2020

Subsidence occurs when the surface [the ground] supporting a property moves downwards, causing the surface to become unstable for the foundations of a building built upon and supported by it. There are many potential causes of subsidence, although, each cause ultimately has the same result. Property subsidence can make properties unsafe and unfit for people to live in. As a result of this, it can have an impact on the value of the property, and make it difficult to sell in the future or secure a mortgage, take out a home improvement loan or otherwise.

To stop the future safety and value of a property from declining, it is important to put preventative measures in for this as early as possible. In addition, knowing what causes subsidence and how to spot the early signs of it are also vital to further protect a home from this type of damage as much as possible.

What Causes Property Subsidence?

Property subsidence occurs when the ground under the foundations of a property sinks. When the ground sinks to a certain point, this will start to affect the physical structure of the building, causing it to become misaligned. There are many different causes for subsidence:

Soil / Clay Shrinkage – One of the most common causes of property subsidence, clay/soil shrinkage means that the amount of soil beneath the building in question decreases, making the surface of the ground move downward, thereby causing some degree of subsidence.

When soil has a high clay content, it has a much higher risk of shrinking in volume. This is because clay is comprised of around 30% water. Therefore, when the roots of nearby vegetation absorb the water from it, the volume of the clay decreases, as does the volume of the soil, leading to subsidence.

Oversaturation of Water in Soil – Oversaturation of water in soil can cause subsidence in multiple ways. When water leaks into the soil in substantial amounts or for a long period of time, the smaller particles of the soil wash away, causing the volume of the ground to decrease, and the surface to fall.

Another way in which oversaturation of water in the soil can cause property subsidence is when the oversaturation makes the soil soften. When this happens, the ground will lose much of its ability to properly and safely support the foundations of a building, causing it to fall or subside.

Properties Built on Old Mining Areas – Areas where mining activities used to occur, such as in old mining towns can also contribute to the subsidence of a property. If an underground mine collapses, this causes a fall in the volume of the ground supporting the house, leading to a downfall in the surface, and therefore at least some degree of property subsidence.

Is Subsidence Covered by Home Insurance?

Home insurance policies are designed to protect you against damage to the physical building and structure of a property as well as its fixtures and fittings. Unlike contents insurance which covers the items within a property, home insurance (sometimes referred to as ‘house insurance' or 'buildings insurance') providers will very often cover any associated loss or damage to the property as a direct result of property subsidence.

However, there are aspects for which they are less likely and not always obliged to pay for. Ultimately it comes down to the insurer and the underwriter’s definition of what is covered under your policy. For example, patios and elements of your garden may not be covered whereas the property itself will be.

Therefore, particularly if there is an increased risk to your property of any subsidence, you should seek a comprehensive subsidence insurance policy which will likely be taken out under your home insurance policy.

What Are the Signs of Subsidence?

There are various different visual indicators that a property is suffering or at least beginning to suffer from subsidence, some of the mains symptoms being as follows:

Existing cracks expanding
Cracks developing after a period of dry weather
Cracks in either the walls (both inside and outside) and the ceilings
Doors and windows getting stiff or will no longer open

It is vital to seek help as soon as any signs of subsidence are noticed, as this can help to minimise its damage to the property. It is always best to check if a property is at risk of subsidence before waiting for the signs to appear, so that effective preventative measures can be put in place.

Which Properties Are Most at Risk of Subsidence?

From the climate to the soil content, different features can cause a property to become at risk of subsidence. Some of the main features that can make a property at-risk of property subsidence include:

Frequent or large water leaks
Drought
High clay content in the soil
Lots of trees or large shrubbery surrounding the house
Being on a site that hosted previous mining activities

Understanding whether a property is at risk of subsidence can help a home owner to more effectively protect their homes from subsidence.

Can You Prevent Subsidence?

Once a property has been identified as at-risk of subsidence, there are a few steps that can be taken to reduce the risk of subsidence actually manifesting. Two of the main ways home owners can help to protect their homes from subsidence are paying attention to the location of trees and large shrubbery surrounding the house and targeting any potential water leakage points.

Ensuring that all trees and large shrubberies are not planted within a 10-metre radius of the property can help to reduce the risk of their roots absorbing too much water from the soil, leading to reductions in the soil volume and the ground’s stability.

Attempting to fix any potential water leakage points can also help to reduce the risk of property subsidence; helping to prevent the soil from washing away or getting too soft to support the property’s foundations. It should also be noted that UK Building Regulations are in part designed to help prevent things like subsidence in buildings so that there is never an isue for property owners.

Can You Fix Subsidence in a Property?

Whether subsidence can be fixed will depend entirely on what caused the subsidence in the first place. If this was caused by the roots of a tree absorbing too much water the tree can be removed to stop this. However, this action should only ever be taken after consultation with a surveyor. It is also important to enlist the help of a tree surgeon for this removal.

Underpinning a property’s foundations is another incredibly effective way to prevent further property subsidence. With underpinning, a solid foundation is placed under the property to support it, thereby preventing further damage due to the surface downfall.