Subsidence: What it is and what to do about it

Subsidence: What it is and what to do about it
Subsidence can be devastating for a property and for its owners.

But it doesn't always need to be a reason for panic, or for walking away from a purchase.

This guide will take you through what to do if the property you own, are buying, or renting out, has an issue with subsidence.

What is subsidence? A guide to proofing your home

Subsidence in a house is when the ground underneath the property becomes unstable and sinks.

When the ground is sinking at different rates across the foundation of the property, this can cause it to become 'lopsided'.


What are the signs of subsidence?

If you spot a crack in a wall then your home could have a subsidence issue.

However, many homeowners recoil in panic at the mere sign of a crack on an internal wall when, actually, the problem may not be subsidence at all.

A single hairline crack on an internal wall is far more likely to be the result of walls or ceilings swelling or contracting in varying temperatures.

Indeed, new-build homes often develop cracks in walls and ceilings early on as the property settles into the foundation or plaster dries fully on walls.

However, if you spot a crack wider than the width of a 10p coin (around 3mm), your property could have a subsidence problem.

Further signs of subsidence can include:

  *  Diagonal cracks
  *  Cracks visible on interior and exterior walls
  *  Cracks that are wider at the top than the bottom
  *  A crack close to a door or window
  *  Doors or windows sticking
  *  Rippling wallpaper


What factors can cause subsidence?

It's estimated that around 70% of subsidence in properties is caused by plants and trees.

Large trees and shrubs can drain moisture from soil, so if they are planted close to a house, the soil underneath the foundation can dry out, causing the property to sink.

Soil heavy in clay can also be a problem as clay dries out and contracts and expands in different weather.

And, yes, weather can also be a factor.

Soil dries out in extremely dry weather so if your area is prone to drought, your property could be at a greater risk of subsidence.

Finally, properties built near to old quarries or landfill sites can also be at greater risk of subsidence due to shifting material, while ageing properties could be built on shallower foundations.


How to stop or prevent subsidence

While subsidence that is already occurring can sometimes be difficult to halt in its tracks without structural work, there are things homeowners can do to lessen the risks and help stabilise an affected house.

Trees close to properties are a big cause of subsidence, so avoid planting any trees or large shrubs within 10 metres of your home.

Large trees should be kept at least 40 metres from your property.

Overly-wet soil is also a big issue for properties and can cause subsidence, so try to catch excess rain water with water butts and properly maintain your guttering, plumbing and downpipes to avoid leaks.


Structural work and underpinning

Major structural work, or underpinning, where a property's foundation is strengthened, is usually only recommended as a last resort.

Costs for this kind of major work can run into tens of thousands of pounds so usually other avenues of remedial work will be explored.

Often, removing a tree near to a property will rectify subsidence but sometimes this can cause a reverse effect known as 'heave' where the ground underneath a property swells due to excess moisture.

Tree removal scenarios should be undertaken by experts who will be able to advise on tree and root control processes.


What should I do if I suspect subsidence?

The first thing to do is contact your buildings insurance provider.

They should be able to send an expert to assess the problem and advise on potential costs, as well as recommending a further course of action to fix the problem.


Buying a house with subsidence

When viewing properties, always keep an eye out for signs of subsidence.

And ask the seller or estate agent about the property's history and if any issues with subsidence have occurred before.

If you suspect a property you are keen to buy may have an issue with or history of subsidence, ensure you have a full structural survey carried out.

This should reveal any issues and allow you to make a judgement on whether or not the property is right for you.

If the vendor or agent confirms work has previously been carried out to remedy subsidence, ensure your solicitor or conveyancer obtains the necessary documents showing the work was carried out to regulatory standards.