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Underpinned house insurance

Kim Jones
Kim Jones
Updated 21 December 2021  | 4 mins read

Getting home buildings insurance for a property that’s been affected by subsidence and underpinned can prove problematic.

There are insurers out there that will cover you, but your choice will be limited and your home insurance premiums could end up being costly.

Read on for how to spot subsidence, what underpinning entails and how it can affect your insurance.

Key points

  • Underpinning is a construction method used to strengthen the foundations of a building affected by subsidence
  • Obtaining buildings insurance for a property that’s been underpinned can be more difficult than normal, but there are insurers that will cover you
  • If you’re considering buying a property that’s been underpinned, ask for a Certificate of Structural Adequacy or a structural engineer’s report to show that all subsidence issues have been fully resolved

What does underpinning a house mean?

Underpinning is a construction process used to strengthen the foundations of a building. It’s mostly used on houses that have been affected by subsidence.

Subsidence happens when the ground beneath a property sinks, pulling its foundations down with it. This movement damages the structure of the building, causing cracks and potentially making it unstable.

There are various methods of underpinning, including:

  • Strengthening the soil by injecting the ground with geopolymer resin
  • Excavating the ground and filling sections with concrete
  • Installing concrete beams
  • Screw piles and brackets

Why are houses underpinned?

Underpinning is usually carried out to remedy subsidence issues and to make a home stable again. It’s usually done as a last resort when other methods aren’t adequate or have failed. It can be a costly, long and disruptive undertaking.

According to the Royal Institution of Chartered Surveyors (RICS), it’s estimated that less than 10% of properties that have subsidence need underpinning. In most instances the problem can be solved more easily.

For example, if the subsidence is happening because a tree near your property is drying out the ground, then removing the tree or cutting it back can solve the issue.

Or if plumbing leaks are washing away the soil beneath your home and causing your foundations to sink, then simply fixing the leak can stop the problem.

After this, it’s a case of monitoring whether the subsidence stops or continues.

If the problem persists, then underpinning may be needed.

Houses may also need underpinning if you’re adding another floor or an extension to your property. In some cases, existing foundations may not be strong enough to take the extra weight.

How much does underpinning cost?

It depends on the method used and whether or not the whole of the property’s foundations require underpinning.

RICS estimate that it can cost anywhere between £5,000 and £50,000. In some cases it could cost even more.

What happens to my home insurance?

Your current insurer should continue to offer you subsidence cover after underpinning work has been carried out on your property.

However, if premiums become too expensive or they can no longer provide cover, then you’ll need to shop around.

Not all insurers will provide quotes for subsidence cover on a property that’s recently been underpinned. Some feel it’s too much of a risk and that an underpinned home may need additional structural work in the future.

Other providers may charge higher premiums and excesses or include lots of exclusions.

However, if the underpinning happened a long time ago and the property has shown no further signs of subsidence, then you should have no problem getting affordable cover.

If you’re having difficulty then it’s a good idea to speak to a broker who works with insurers that specialise in offering cover for underpinned homes.

Should I buy a house that has been previously underpinned (PUP)?

Alarm bells might ring if you discover that the house you want to buy is a PUP.

You needn’t discount it outright, though. 

Many homes that have had subsidence issues in the past get bought, sold and insured every year without problem.

Your solicitor will need to request proof from the seller that the subsidence has been remedied and isn't ongoing. This can be in the form of a Building Regulations Completion Certificate and a Certificate of Structural Adequacy (CSA).

It’s also advisable to pay for a full structural survey by a structural engineer rather than a standard homebuyers’ survey.

You may want to negotiate on the price, especially if you were unaware of the underpinning before you made your initial offer.

Be aware that you may find it more difficult than normal to sell your home when the time comes, just because some buyers will be put off by properties with a history of subsidence.

Can I get a mortgage on a house that has been underpinned?

If a full structural survey confirms that the underpinning is of a high standard and the house has no ongoing movement, you’re likely to be able to get buildings insurance on the property. This would mean that most lenders would be happy to provide a mortgage.

You may want to think about using a broker to help you search for lenders that offer mortgages on properties that have been underpinned. A broker specialising in non-standard insurance could help you find competitive quotes.

Do you need to declare underpinning when selling your house?

Yes, you should be upfront about the fact that your property has been underpinned.

Buyers are protected by The Misrepresentation Act 1967 and can sue sellers if they think they’ve being misled about previous work on a property.

How do I spot subsidence?

Usually, the first indication that subsidence might be happening is cracks appearing on your walls.

Don’t worry though as most cracks are harmless. They’re often the result of settlement in newer buildings, or thermal cracking which happens as buildings expand in the heat and contract in lower temperatures.

However, some cracks can be a sign of structural damage and subsidence.

Typically these sorts of cracks might:

  • Measure more than 2mm wide along their full extent and run diagonally
  • Be more than 5mm wide at any point in the crack
  • Be wide at one end and narrow at the other
  • Be visible on both the inside and outside walls
  • Have become wider or longer over time
  • Appear at weak spots, like around doors or windows

As well as wide cracks appearing, signs of subsidence can include:

  • Gaps appearing between the floors and walls
  • Sloping, uneven floors
  • Cracks in concrete floors and in garden paths
  • Doors and windows that become difficult to open and close tight
  • Cracks that appear on exterior brick walls that are zig-zagged and follow the lines of mortar

Is there a risk that my home will have subsidence?

Any property could suffer from subsidence but some are more at risk than others. These include:

  • Homes built on clay soil - in warm weather, as water in the ground evaporates and the earth dries out, clay-rich soils tend to shrink. This can cause downward movement and subsidence. Clay soils are particularly prevalent in London and the South East
  • Homes built where mining has taken place in the past
  • Properties with poor drainage that easily becomes waterlogged
  • Houses in areas prone to flooding built on sand or gravel soil, which is more prone to being washed away
  • Houses surrounded by trees - trees absorb a lot of moisture from the soil, and can cause it to shrink and erode

What do I do if I spot subsidence?

If you suspect that cracks in your home are caused by subsidence, you should contact your insurer as soon as possible.

They can send a loss adjuster or surveyor to your home to investigate.

They may be able to determine instantly that the cracks are harmless.

If they suspect subsidence, in most instances, a surveyor will want to monitor the cracks to determine whether there's movement. This can take around 12 months.

If subsidence is confirmed, the surveyor and your insurer will decide on the best course of action.

Do I need specialist underpinning insurance?

Some mainstream insurance companies won’t provide quotes for homes that have been previously underpinned or that are in areas prone to subsidence issues. So, your choice of insurers will be more limited. 

There are lots of companies that are prepared to cover underpinned homes though, especially if it happened 10 or more years ago and the property has experienced no structural issues since.

Insurers will want to know when the subsidence occurred, the cause of it and the exact method and extent of the underpinning. They’ll also want proof that the subsidence has stopped and that your property’s superstructure is now stable.

You may find that many insurers will ask for a higher excess than the typical £1,000 for a standard policy.

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