Subsidence is one of the most serious problems you can encounter as a homeowner, with the potential to cause serious damage to your property, resulting in hefty repair bills.

The best way to prevent subsidence and avoid having to deal with its consequences is to understand which warning signs to look out for and what you can do to stop the problem from getting worse.

In this article, we’ll look at what subsidence is, what causes it, telltale signs of subsidence, and what to do if you suspect that your home might be affected.

What is subsidence and what causes it?

Subsidence is a term that describes the damage that occurs when the ground underneath a property begins to sink. This can damage the foundations of the property, particularly if different parts of the ground are sinking at different rates.

Subsidence can either exist as “historic” subsidence or “active” subsidence. Historic subsidence refers to subsidence that has been an issue in the past but has since been solved or repaired; this does not present immediate issues for the structure of the property, but it may affect its market value. Active subsidence describes subsidence that is ongoing and causing problems for the structure of the property.

What causes subsidence?

Subsidence is caused by movements in the ground’s surface that the property is built on, which usually happens as a result of changes in moisture levels. This can happen for a number of reasons, but the most common cause is the roots of nearby trees absorbing moisture in the soil, causing areas of the ground to dry out and sink. Another common cause is when a water pipe in or near the property leaks, softening the ground and causing the property to sink.

Subsidence may also occur if the property is built on clay soil, which is a variety of soil that is susceptible to changing consistency depending on the weather. In wet weather, clay soil can swell, whereas it can crack in hot and dry weather, meaning that a property with foundations on clay soil may be prone to becoming unstable.

A property may also sometimes be affected if it’s situated near a former quarry. As the material used to fill the site gradually decomposes, this can cause shifts in the ground’s level.

Is subsidence the same as heave or settlement?

Subsidence is sometimes confused with both heave and settlement, though these property issues are slightly different.

Settlement also describes when a property sinks, but in this case, it’s specifically when this occurs because of the excessive weight of the property itself, causing the soil to compress. This is also known as compaction.

Heave refers to a scenario when the ground under a property rises, for a number of possible reasons, causing the property to shift upwards.

Could subsidence affect my home?

Certain properties are more at risk of subsidence than others. The factors that affect this include:

  • The age of the property – older properties may have shallower foundations, putting them at increased subsidence risk, though this is not a strict rule. 
  • Clay soil – as mentioned, clay soil is susceptible to shifting due to changes in the weather, meaning a property built on clay soil is at increased subsidence risk.
  • Drought – areas prone to drought can be more at risk of subsidence issues, as dry soil can start to crack and shift.

What are the signs of subsidence?

It’s worth knowing the key signs of subsidence to look out for so you can act quickly if it presents a problem for your home.

The main sign of subsidence is thick cracks appearing in the property. However, cracks do not necessarily indicate subsidence, and are often simply the result of temperature-induced swelling or shrinking in your home over time. Cracks only tend to indicate subsidence issues if they have a particular appearance and occur in particular places.

Cracks may be caused by subsidence if they are:

  • Over 3mm wide (more than the width of a 10p coin)
  • Wider at the top and slimmer at the bottom
  • Diagonal
  • Positioned near doorways and windows
  • Visible from both inside and outside.

Other potential signs of subsidence include wallpaper creasing where it meets the ceiling and door frames and window frames warping, meaning doors and windows may stick.

What should I do if my home is affected by subsidence?

You should act as quickly as possible if you suspect your home may be affected by subsidence, as putting off finding a solution may allow the problem to get worse.

If you’re confident that your home is suffering from subsidence then start by contacting your buildings insurer. They will help arrange a survey on the property from a structural engineer to confirm whether it is affected by subsidence and what may be causing it. Be aware that they might not be able to give you an answer straight away, and your property may require monitoring over a period of several months to confirm whether subsidence is an issue. You may need to get drain surveys or geographical surveys covered out to ascertain the cause of the issue as well.

You can also get a subsidence survey done on your own without going through your insurer first. This can sometimes be a better option, as some insurers have been known to increase their customers’ premiums after a subsidence check even when no subsidence is found, but the downside is that you will be paying for the survey yourself.

Once you know whether your home is affected by subsidence and the extent of the problem, there are a few potential solutions. Your surveyor and insurer will let you know the best option.

  • Underpinning

Underpinning refers to having your foundations strengthened in order to protect against subsidence. This is usually only necessary in the most serious cases of subsidence, with the Royal Institute of Chartered Surveyors (RICS) estimating that of all properties affected by subsidence, less than 10% require underpinning. While it is an expensive process, the cost can be significantly lowered if subsidence is covered by your buildings insurance.

  • Tree maintenance or removal

If subsidence is caused by the roots of a tree near the property disrupting the ground then having the tree felled will often solve the problem, although pruning it sufficiently may also stop the problem. A structural engineer and tree surgeon will be able to advise on the best solution. If the tree belongs to someone else then they still have to get rid of it if it’s causing you subsidence issues, and they may be liable for repair costs to your property.

  • Pipework

If subsidence is caused by a burst pipe or leaky drain then getting these repaired will usually solve the issue.

  • Resin

A more recent solution to subsidence issues is to inject quick-hardening resin into the ground around the building to reinforce the foundations. This is less expensive and disruptive than underpinning, and your surveyor and insurer can let you know if it is a viable solution.

What can I do to prevent subsidence from occurring?

There are a couple of easy ways to avoid subsidence becoming a risk to your home.

Be careful if you are considering planting a tree or scrub near your property. Ideally, avoid planting any tree within 10 metres of your property, and any particularly large trees should be at least 40 metres away. Regularly pruning existing trees on your property can help to regulate their moisture intake as well.

In addition, aim to keep your guttering and pipework well-maintained to prevent any leakage that could lead to subsidence.

Will subsidence affect my property’s value?

There is no getting around the fact that subsidence can affect your property’s value,  potentially decreasing this by around 20%. Even if subsidence is not an active issue any more – that is, it is now “historic” subsidence – this will still affect the property’s value.

A history of subsidence – and especially ongoing issues with subsidence – can also make it more difficult to secure a mortgage on a property, meaning it may take much longer to either buy or sell.

Speaking to an experienced mortgage advisor can help you to understand your options and get a great deal on your mortgage. If you’re looking for expert mortgage advice, you can speak to an independent mortgage broker with Unbiased. Every advisor you find through Unbiased will be FCA-regulated, qualified and unconnected to product providers – so they can offer you truly unbiased advice.

If you’re looking to sell a property that is suffering from subsidence or has historic subsidence, you must declare the issue to any estate agents or buyers.

Is subsidence covered by buildings insurance?

Almost all buildings insurance policies cover the cost of surveys and repairs in the event of subsidence, unless the property has been affected by subsidence in the past.

While the excess that you pay for subsidence treatment is usually high (around £1,000), this is usually well worth it, particularly if underpinning needs to be performed. Your policy will cover repairs to damage caused by subsidence, and if the issue is serious enough that you need to temporarily seek alternative accommodation, your insurer will usually cover the cost of this too.

You should contact your insurer or double-check your policy to find out the exact extent of your subsidence cover if you’re concerned that it may be an issue.

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