Subsidence – it might possibly be any property owner’s worst nightmare as an article suggests. Putting right the problems caused by subsidence may prove very expensive and leave the property uninhabitable during the remedial works, and it requires specialist subsidence insurance going forward.

To cap it all, though, many home, landlord and small business property insurance policies do not cover the risk of subsidence as standard.

What is subsidence?

The Association of British Insurers (ABI) has published a simple and straightforward guide entitled “Protecting your home from subsidence damage”.

The guide identifies the root problem of subsidence being the collapse of ground supporting the foundations on which a property is built. The principal causes are:

• ground – especially clay soils – shrinking as it dries out, leading to a collapse of its load bearing capacity; or

• the expansion of foundation bearing ground as it absorbs water from damaged or leaking drains or water supply pipes underground.

What causes it?

Past mining operations, ground that has not been properly compacted or broken and leaking pipes may be responsible for some forms of subsidence, but it is widely accepted that one of the most common culprits are trees growing too close to the building.

The roots of trees absorb water for nourishment, leading to a natural drying out of the soil in which the roots are growing. During periods of sustained dry weather or drought, the roots are forced to spread out even further and dig deeper in search of the water they need, thus leading to still further shrinkage in the soil supporting the foundations of a property.

Preventing it

Preventing subsidence might not be quite as straight forward as it may appear. If trees are causing the problem, for example, why not simply remove them and stop the roots drying out the ground and causing it to shrink?

If the tree is removed, drying out of the ground is indeed likely to be halted, but the opposite then occurs as the ground soaks up too much moisture, causing it to swell and put any building at the risk of the still more serious of heave.

Advice from the ABI on the prevention of subsidence, therefore, is somewhat more selective and may be summarised as follows:

• do not plant large shrubs or trees near to the property in the first place;

• if trees were planted too near to the building after it had been built, they may need to be removed;

• if the trees are older than the property itself, however, their removal may cause the ground to swell and lead to building heave – they are best left in place;

• if trees need to be left in place, their growth – and the growth of their roots may nevertheless be managed, either by pollarding or by a reduction in the amount of foliage and hence the uptake of water from the ground.

Given the seriousness of subsidence if it should occur, you might want to check your buildings insurance as carefully as possible. It may be that you hear the risk described as a non-standard peril and therefore one that you might want to entrust to the services of an experienced specialist provider of subsidence insurance – such as those of us here at GSI Insurance.

Further reading: Guide to Subsidence Insurance