Everything You Need To Know About Subsidence In Sixty Seconds

15/11/2016

Nothing strikes fear into the heart of a building owner like subsidence.  It is one of the most serious problems a property can suffer, affecting its structural safety and resale value.

Over the last 10 years the adverse effects of subsidence caused by shrink-swell behaviour of soil have cost the economy an estimated £3 billion, making it the most damaging geohazard in Britain today. As many as one-in-five homes in England and Wales are likely to be damaged by ground that swells when it gets wet and shrinks as it dries out.  Furthermore, European research (undertaken by Swiss RE and the Swiss Institute of Technology) in July 2011 warned that climate change could magnify the already significant problem of property damage as a result of subsidence. 

The new model predicts subsidence will worsen and spread in Europe with some areas seeing more than a 50% increase in the next 25 years. This follows an actual 50% increase we see today compared with the period 1951-1970. Although subsidence is usually covered by your insurance policy, a subsidence claim will have to be disclosed if you decide to sell the property and this may affect the ability of a potential buyer to secure a mortgage on the property.

What is subsidence?

Subsidence occurs when there is a loss of support beneath the foundations of a building, causing it to move downwards and suffer cracking as a result.

The key element of the definition of subsidence which distinguishes it from “settlement” is the factor of the weight of the building. Where the property sinks “into” the site upon which it is built then this is generally indicative of inadequate design / construction. Where the site moves downward, and would have so moved even if there was no building upon it, then this is generally regarded as subsidence.

What causes subsidence?

There are four common cause of subsidence (some are more likely to occur depending on geography):

Soil shrinkage accounts for around 75% of subsidence claims in the UK.  Cohesive soils such as clay and silt vary in their ability to change their volume when wetted or dried (known as volumetric change), therefore when wet they will expand (swell) and when dry they will shrink.

Clay is particularly prone to ‘shrink-swell’ and is found extensively across England and Wales. 

Tree roots absorb water for photosynthesis and moisture evaporates from the leaves through transpiration. The active period is predominantly in spring and early summer when tree growth is at its maximum. With larger trees in shrinkable clay soil, the tree can extract sufficient moisture to cause soil shrinkage and hence may lead to building subsidence.

In most soils there tends to be a mixture of different soil types, including clay, which allows for many species of tree to grow deep enough to negatively affect buildings whose foundations have not been laid deep enough.

Most trees in the UK have a significant radial root system, extending one to one-and-a-half times the height of the tree.  It is always recommended that construction takes place as far away from trees and established vegetation as possible, because the distance at which tree roots can detrimentally affect a building (known as the ‘zone of influence) is quite significant. 

Why are can settling subsidence claims sometimes be complex?

Typically, subsidence claims can take a long time to settle with insurers.  This is because once the issue of breach and causation is established, the decision on how best to resolve the problem can be subject to considerable debate.

Determining the best resolution for the building is often a lengthy process and will depend on a number of variables. These include:

• the make-up of the soil underlying the foundations          

• the consistency of that make-up          

• the nature of the foundations          

• the trigger(s) for the movement and          

• (once the situation is clear) the options for repair.

In the event of subsidence, both insurers and policyholders are likely to require reports from specialist engineering/structural experts and loss adjusters.  This can lead to further delays, which if not communicated to the insured can lead to frustration.

Complications can also arise if the policyholder changed insurers around the time when - as later becomes evident - subsidence movement and damage was already occurring (possibly without the policyholder's knowledge). In these circumstances, the ABI (Association of British Insurers) Domestic Subsidence Agreement states that one of the two insurers should deal with the claim, even if it includes damage that occurred during the other's period of cover.  This only applies to insurers who subscribe to the agreement and the does not apply where a property has changed hands - and there has been a change of policyholder.

In summary

Subsidence can cause devastating damage to buildings and considerable stress and frustration for the insured and the insurer due to the complex mature of making and settling a claim.  Engaging an expert solicitor who understands the nature of subsidence claims can help speed up the resolution and advise on any policy issues encountered during the process.