What do subsidence cracks look like?

There has been an increase in hot, dry weather in the UK in recent years, which can put homes at greater risk of subsidence.

Subsidence happens when the ground under a property collapses or sinks lower. This uneven movement may result in structural damage such as cracks in walls, floors and ceilings, which can be expensive to repair. We show you how to spot subsidence cracks and what to do about them.

MUST KNOW

If you spot a crack, use a 10p coin to test how wide it is. If it’s thicker than the coin, you might have a problem as subsidence cracks tend to be more than 3mm in width.

IN SHORT

WHAT ARE THE SIGNS OF SUBSIDENCE?

It’s important to be aware of what subsidence cracks look like so you can spot them early and resolve the problem before it develops into something serious. The main sign of house subsidence is:

LARGE CRACKS IN WALLS

The biggest tell-tale sign of subsidence is usually the appearance of cracks in your home’s walls, either in the outside brickwork or indoor plasterwork. Subsidence cracks have distinct characteristics. They usually appear suddenly, especially after a long dry spell, and are typically:

• Spread diagonally or stepped across brickwork
• Wider at the top than at the bottom
• Found close to doors and windows
• Wider than 3mm
  
  

Other warning signs of subsidence can include:

DOORS AND WINDOWS STICKING

If your doors and windows have started sticking for no obvious reason, there could be a problem. House subsidence causes window and door frames to warp. Cracks or gaps may also appear around your windows and door frames.

SINKING FLOORS

Sinking or sloping floors can indicate that the ground beneath your property is collapsing. Skirting boards separating from the wall also suggest your home could be experiencing serious movement issues.

That said, sloping floors in older properties could just signify past movement rather than an ongoing subsidence problem.

WRINKLED WALLPAPER

Another sign of house subsidence is creased or wrinkled wallpaper where the wall meets the ceiling. The most likely cause is damp, but you may have a more serious issue if the area is bone dry.

WHAT ARE THE CAUSES OF SUBSIDENCE?

There are many potential causes of subsidence that you should be aware of. The most common ones are:

• CLAY SOIL

Houses built on clay soil – common in London and the south east – are at particular risk of subsidence in a prolonged dry spell. That’s because it shrinks, cracks and shifts during hot weather when there’s less moisture in the ground. In wet conditions, it swells.

• TREES AND SHRUBS

Roots from trees and shrubs take water from the soil, drying it out and causing it to shrink. This can be a problem if they’re close to the foundations of your home.

Poplars, willows and oaks are among the worst culprits as they have long fine root structures, which means they can drink huge amounts of water each day and dry out gardens. Mature trees may remove more than 50,000 litres^[1] out of the ground each year.

• LEAKING DRAINS

Another cause of house subsidence is water leaking into the soil from damaged drains. This washes soil away from a building’s foundations and can cause the house to sink because the ground under it may be too unstable to hold its weight.

DO CRACKS ALWAYS MEAN SUBSIDENCE?

If a crack appears, don’t panic – it doesn’t necessarily mean subsidence. It’s normal for some houses to have minor cracks that have nothing to do with ground movement. Also, some movement in a house’s foundations is normal and won’t necessarily cause damage.

Narrow, hairline cracks can usually be dealt with during routine maintenance or when you’re redecorating.

If you’re concerned, get in touch with your home insurance provider who will be able to help. An experienced builder may also be able to detect signs of subsidence, but a chartered surveyor or structural engineer would carry out a formal survey.

IS SUBSIDENCE COVERED BY MY HOME INSURANCE?

Most buildings insurance policies will cover damage caused to the structure of your property by subsidence. However, you’re likely to have to pay the first £1,000 towards a claim (the excess).

Damage to surrounding structures including garden walls, fences, gates, patios and driveways is not usually covered unless it happens at the same time as the damage to your home.

If you make a claim, your insurance provider will usually arrange for a structural engineer to visit your property to diagnose the issue. Most insurers will also organise repairs with their approved contractors.

If the damage to your home is so severe that the property is uninhabitable, your insurer should cover the cost of alternative accommodation while repairs are being carried out.

HOW CAN I REDUCE THE RISK OF SUBSIDENCE?

While not all subsidence problems are preventable, there are some simple steps you can take to protect your property and limit the risks:

• If you have a tree, you’ll need to ensure you’re looking after it: Manage it, maintain it, reduce it, clip it and control it.
• Don’t plant inappropriate trees too close to your home, garage or outbuildings. The Association of British Insurers ^[1] (ABI) suggests willows should be no closer than 40 metres from the nearest building, poplars 35 metres away and oaks and elms 30 metres away.
• If you’re unsure whether a tree could cause damage, seek professional advice.
  Make sure drains are free flowing. Don’t put the wrong things down drains or create blockages.
  
  

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Sources

[1] https://www.abi.org.uk/globalassets/sitecore/files/documents/publications/public/migrated/home/protecting-your-home-from-subsidence-damage.pdf