Subsidence is a pretty common phenomenon around the UK, due to its climate, with variable rainfall and a mix of warm and cool weather. Many homeowners face severe financial consequences if their properties are affected by subsidence or heave.
 
House owners can be left high and dry if they are not suitably covered by non-standard home insurance as they will not have enough cover with regular policies to cope with such an occurrence. Homeowners who have the slightest suspicion that their property might be affected by subsidence should check with their insurance providers as soon as they can to make sure that they have adequate protection in place.
 
To begin with, there are a few pieces of terminology which are useful to clarify. Subsidence is defined as a downward movement of the earth directly underneath a property. If not treated for a period of time, this movement usually causes structural damage which can be very expensive to put right.
 
 Heave is the upward movement of the ground, which is usually connected to the expansion of clay soils, which swell when wet. The effect of heave is opposite to that of subsidence or settlement, where the weight of a building causes distortion or disruption to parts of the foundations because of unequal levels of ground compression.
 
The Association of British Insurers reports that dry spells can be a cause of subsidence because as the temperature heats up, the ground becomes dry and can contribute to increased movement in the earth beneath some properties.
 
Another common risk factor is a building constructed on soils with high clay content. In fact, London’s earth is known for its high clay content, which obviously has implications for the structures built onto it.
 

What are the main causes of subsidence?

 
There are several factors which might contribute to subsidence in a house or property and indeed, it may be a combination of two or more factors.
 

• A stretch of extended dry weather makes buildings at risk of subsidence particularly vulnerable as they shrink and swell in accordance with their water content. As our climate changes, extreme weather events are causing these periods more frequently, hence the need to check more often than previous times.
• If there are large trees near a property, it could be a trigger for subsidence, as the roots extend under the building and can suck water out of the soil, thus drying it up. Roots from a large tree stretch out and down towards the foundations of your property, removing moisture from the soil and causing it to shrink.
• Ensure that all your water pipes are secure and in good working order, as it has been known for pipes and drainage systems which leak over extended periods to cause the surrounding ground to soften or wash away beneath the foundations.
• Clay soil changes with the weather. When it is hot and dry it can shrink, crack and shift, which makes ground inherently unstable and may cause it to sink unevenly.
• If you live in a period property there may be a greater risk of subsidence as the age and construction method of your house could mean it has more shallow foundations than a more recently-built home. On the other hand, older properties tend to be built from bricks and lime mortar whose characteristics could make them more flexible and less prone to damage caused by shifts in the ground beneath them.
• Mining – If the property was built near to a former quarry or pit, it might be unstable, because the material used to fill in the site will almost certainly shift as it decomposes over the years. Your house could also be affected if mining activity occurs close by. In this event, you can get a subsidence claims report from the Coal Authority to clarify whether your home is affected.

 
Ultimately, where soil type is concerned, it may simply be a case of the postcode  - a greater or lesser risk depending on the property’s location. If unsure, you can easily research this information.
 
Of all the causes listed, subsidence caused by tree roots seems to be statistically the most common source of non-stanadard home insurance claims.
 

Spotting the ‘tell-tale’ signs of subsidence early

 
If you are already living in the property, there are a few tell-tale signs of subsidence that can be recognised through periodic inspection over the years.
 
Look for cracks near the corners of your windows or doors. Or cracks that start small and apperar to get bigger as they go along.
 

How to check for subsidence

 
What is really required is extensive information so that you are able to either pinpoint or eliminate the various causes of subsidence as you investigate each possible reason.
Additionally, older properties built before the Second World War are most susceptible to subsidence as they were built with shallower foundations than required by modern building regulations.
 
The sooner you can identify subsidence the better. During or after spells of hot, dry weather it’s advisable for homeowners to check for the following warning signs on their properties:
 

• Newly formed cracks which are wider at the top and more than 3mm wide in walls. However, bear in mind that not all cracks indicate subsidence as minor cracks are common in most buildings after a while.
• Cracks appearing around vulnerable spots in your home - that means specific points where there are joins and there is a risk of damp or leaks, for example, around doors and windows.
• Particular doors and windows have started to stick, which could be caused by underlying movement.
• If there is an extension built onto the original structure, check for cracks where the extension is connected to the main building. Ground movement would cause the extension to show signs of separating from the main building.

My home has subsidence. What do I do now?

 
Firstly, and it’s worth repeating ad infinitum, get in touch with your home insurer as soon as possible, because the faster the subsidence is diagnosed, the better your chances of putting the problem right. If you have non-standard home insurance, there is probably some kind of provision in your coverage, which is why it’s by far the most advisable option when insuring, particularly when you know that the house has a history of subsidence.
 
In any case, the first step for the insurer is to send a loss adjuster to your house to assess the damage and the potential cost. Your insurance provider is then in a position to recommend what to do if the subsidence is confirmed. You will need the services of a specialist contractor, like a subsidence repair professional. This obviously depends on your cover and the extent of the damage.
 
The most common treatments for subsidence include:

• Underpinning the foundations
• Pruning or removal of trees and bushes
• Repairing damage to drains and pipes

Underpinning

 
Underpinning is the process of strengthening the foundations of a construction, on the load-bearing walls. Underpinning might be required for the more severe effects of subsidence but it’s intended to impede further movement of the foundations. It can be a lengthy and expensive endeavour, with a potential bill of thousands of pounds (of course, this depends on the size of the property and the extent of the damage).
 
It’s hard to get exact statistics, but the general consensus is that only around 10% of properties suffering from subsidence will need to be underpinned, so it certainly isn’t the most common of solutions.
 
Tree root damage is the most common cause of all subsidence cases, as tree roots suck moisture from the soil beneath the property. This problem can become more accentuated during long dry periods, especially in parts of the country where the soil base is formed mainly of clay.
 

Pruning trees and roots

 
There is a very quick solution if the cause of subsidence is the network of roots under the building. Cut the tree down. However, if it sounds too easy to be true, it probably is. Cutting down the tree(s) could result in heave because of excessive moisture caused by the very absence of the tree (if that tree kept moisture levels low). It may be worth contracting the services of an arboriculturalist (tree specialist) to advise you on the best steps to take.
 

Damage to pipework or drainage systems

 
Regarding leaky pipework or burst pipes inside or underneath the foundations, you can have a CCTV drain survey done to clarify whether this is the problem. It isn’t complicated to do repair work on pipes or drainage systems and after a period of waiting to see if the problem is still present or not, it might eliminate the need for expensive underpinning work. 

Buying a house with subsidence

 
Perhaps you may wonder why someone would want to buy a property, knowing that it has problems with subsidence. Moreover, if you are the seller, the nagging question that keeps you awake at night is whether you have it on the market if the signs of subsidence are going to become apparent when the property is surveyed.
 
The fact is, many people live all over the country in properties which have a history of subsidence. Apart from that specific problem, the property itself may be a beautiful, comfortable and desirable building, so it would be unfortunate for a deal to fall through simply due to something which can be rectified.
 
 As this house-buying blog comments, it’s sensible to “keep the threat of subsidence in proportion”, adding a useful reminder that it doesn’t need to be a deal-breaker if dealt with properly; “... even if the roots of that delightful tree in the next-door garden need watching (in case they trigger subsidence) it’s still a lovely tree.”  
 
In some areas, underpinning isn’t seen as such a big deal. London, for example, has predominantly clay soil, so many properties have been underpinned or are in areas classified as ‘at risk’.
 
Despite being the treatment most people associate with subsidence, underpinning the foundations to deepen them and prevent further movement is only recommended as a last resort.
As the roots of trees and bushes extracting moisture from the soil is the most common cause of subsidence, pruning or removing them should sort out the problem. A Chartered Surveyor will inspect the plants and trees surrounding the property and should be able to recommend a specialist that can advise whether the plant ought to be pruned or completed removed.
The most appropriate treatment option will depend on the cause of the subsidence. Your surveyor will advise you on the best course of action for your property.
 

Get documented

 
If the property in question has a history of subsidence, there are two important documents required.

• A formal Completion Certificate, issued by the local council if underpinning has been carried out.
• A Certificate of Structural Adequacy, produced by the Building Surveyor if the repairs were undertaken as an insurance claim.

When you buy a property, it is natural that you will arrange for  a Surveyor’s inspection, and with the resulting report, you will be fully informed about what your options are. The British Insurance Brokers Association (BIBA) is a useful source for reliable information around subsidence and how it affects your status as a buyer or owner searching for non-standard property insurance.
 
This construction wiki also provides useful information about all aspects of subsidence and other common problems connected with this subject, as does the ABI website.
 

Protecting your home with non-standard home insurance

 
Both the formal Completion Certificate and Certificate of Structural Adequacy should be available from the owner of the property, so if your surveyor reports any previous subsidence repair work make sure your conveyancing solicitor obtains the relevant documentation.
 
Nevertheless, because it’s classified as non-standard for insurance purposes, it’s important to find the appropriate cover for your needs. At Insurance Choice, we help homeowners struggling to find home insurance for their non-standard properties.  Get a quote for non-standard home insurance from us and we’ll help you obtain  the right solution.