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Cracks in the walls of your home

Cracks in the walls of your home are never a pleasant sight. But while most are just a decorative nuisance and can easily be fixed, some are a major cause for concern. Read on to find out more.

Cracks in the walls of your home are never a pleasant sight. But while most are just a decorative nuisance and can easily be fixed, some are a major cause for concern. Read on to find out more.

Written by
Anna McEntee
Insurance comparison expert
Last Updated
7 JUNE 2024
6 min read
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What causes cracks in the walls of my home? 

It’s likely your house will experience cracks in the walls at some point. Most of the time, it’s perfectly normal. Here are some of the common causes of cracks in homes:

  • Leaks caused by escape of water somewhere in your house.

  • A new build or extension ‘settling’ into its foundations.

  • Changing temperatures and humidity levels causing the structure to shrink and swell over time.

  • Newly plastered walls cracking as they dry out.

  • Traffic vibration from nearby busy roads.

  • Fitting uPVC double glazing without a supporting lintel.

Do cracks mean subsidence?

Cracks caused by the above tend to be superficial and can be easily fixed. But anything larger could be the sign of serious structural problems, like damage to the foundations or subsidence issues.

Larger cracks can be caused by:

  • Water damage and underground leaks. 
  • Roots from nearby trees that spread into the foundations and suck away moisture from the soil below your home. 
  • Flooding and heavy rainfall, especially in clay soil areas.
  • Prolonged dry weather
  • Poor foundations – older buildings can sometimes have much shallower foundations than modern buildings, making them potentially less stable. Poor materials can also allow buildings of any age to shift.
  • Mining – in some parts of the UK, local underground mines, including those long-disused, can cause damage.
  • Lintel failure – where support for the brickwork above the opening of a window or door is poor or non-existent. Look for diagonal cracks, sometimes mistaken for subsidence.

When should I worry about cracks in the walls and ceilings?

There’s usually no need to worry about small or hairline cracks. However, larger cracks may be a sign of something more serious. 

If you have any of the following cracks in your home, it might be best to get them checked out by a structural engineer:

  • Cracks that are more than 15mm in width
  • Cracks that appear suddenly, rather than slowly over time
  • Cracks that run diagonally
  • Cracks above doors and windows
  • Cracks that allow daylight in.

Different types of cracks:

No wall crack is the same. They can vary in length, width and direction. Typically, larger cracks (those bigger than 15mm in width) are a cause for concern, as they could point to structural issues. You’ll want to get these inspected by a structural engineer.

The following table can help you assess how severe cracks in your home could be and what you might need to do to fix the problem.

Size (width) Severity Action required
Less than 1mm No cause for concern Can be easily fixed with a bit of DIY
1mm-5mm Slight Can be fixed with filler. Exterior cracks may need repointing
5mm-15mm Moderate May need professional building repair work
15mm-25mm Serious Should be inspected and repaired by a professional
More than 25mm Very severe May require major foundation repair work, including underpinning and rebuilding


Vertical cracks

These kinds of small cracks often appear in plastered walls in new properties. They can happen when the plaster expands in humidity and shrinks as it dries.

It’s best to wait a while before filling these small cracks and repainting them, as more could appear.

If vertical cracks are wider than 5mm, there could be a more serious cause, which should be investigated.

Horizontal cracks

These could be the result of structural movement. These sorts of foundation problems should be taken seriously.

Diagonal cracks

These are also known as stair-step cracks, like a set of stairs going along your wall. They could be a sign of structural movement. Take them seriously.

Some diagonal cracks around door frames and windows can appear because the lintel above is missing, weak or badly installed. It’s best to get expert help to determine the cause of the problem.

Ceiling cracks

These could be caused by several things, including plaster shrinkage, damp and structural movement. Because of this, it’s best to have them inspected by a professional.

Repairing a drywall ceiling isn’t as easy as repairing a crack in an internal wall, so you should consider getting a professional to repair it to a good standard.

Structural cracks

These tend to follow a pattern that mirrors the movement and shifting of the building. They could be a sign of an underlying structural problem that will need to be investigated further.

How can I prevent cracks in my walls?

It can be difficult to prevent cracks forming in the walls of your home, because the cause of the crack is rarely visible before the damage is done.

One thing you can do is check for any drainage issues and leaky pipes. Water damage is a cause of severe cracks forming, so preventing this is a good step in protecting your home.

If you live in an area that’s prone to subsidence, you should avoid disrupting the land as much as possible.

Don’t plant large trees and plants close to your home, as their roots can dry out the soil close to the foundations. On the other hand, removing a long-standing tree can cause a sudden build-up of moisture, which could cause other problems.

How to fix cracks in walls

If it’s a superficial or minor crack, you may be able to fix it with a bit of DIY. Simply use some filler to cover the crack, wait for it to dry, sand it and then paint.

If it’s a more severe crack and you’re worried about potential structural damage, you should consult a professional structural engineer immediately.

They’ll monitor the cracks to see if any movement has stopped, or if the structure is still moving and requires further investigation.

Are cracks in my home covered by my buildings insurance? 

For homeowners, cracks caused by subsidence should be covered by your buildings insurance. But you’ll have to pay an excess, which is often larger than for other claims on your policy. 

If you do make a claim, your insurance provider will sometimes want to monitor the crack before deciding on how best to remedy the situation. You’ll also need to declare subsidence issues when comparing or applying for home insurance in the future. 

If the cracks are caused by a leak, they should be covered by your buildings insurance under ‘escape of water’ damage

Buildings insurance won’t typically cover cracks caused by:

  • Natural settlement
  • Thermal movement
  • Maintenance issues, such as lintel failure
  • Wear and tear
  • Normal deterioration

If you’re not sure what’s covered, check your policy documents or contact your buildings insurance provider.

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Frequently asked questions

Why does a hairline crack in a wall keep coming back?

A recurring hairline crack could be a sign of structural damage. If the crack in your wall keeps coming back, it should be inspected by a structural engineer.

Why is my plaster cracking when drying?

New plaster cracks are caused by moisture loss as the plaster dries and sets. High temperatures, sunlight and drafts can cause the plaster to shrink and dry too quickly. 

To help reduce plaster cracks, try to slow down the drying time by keeping the room dark and free of drafts.

Will claiming for a crack affect my insurance?

Claiming for a crack could affect your insurance, especially if it’s subsidence-related.

Providers consider customers who’ve claimed for subsidence more likely to make another claim in the future. This means you could well see an increase in your premium come renewal time. Your no-claims discount if you have one, may also be affected.

Can I claim for repairing cracks in my outbuildings?

It’s always best to check your policy or contact your provider before doing any repair work yourself.

You may want your home insurance provider to confirm if the crack is caused by subsidence. Or the crack may require monitoring over time to see if it grows or not to ascertain how serious it is.

For large claims, insurance providers will most likely send someone out to assess the damage and use their own approved repairers to carry out the work.

Can I claim for repairing cracks in my outbuilding?

You may be able to claim for repairing cracks in your outbuilding if it’s included in your buildings insurance. Be sure to check your policy, though, as not all providers include cover for outbuildings and garages as standard.

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Anna McEntee - Home, pet and travel insurance expert

Anna’s all about delivering fantastic insurance products at a great price. Value is the most important thing for Anna, as she cuts through the jargon and finds what’s most important and worth your hard-earned money.

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