What causes cracks in the walls of my home? 

Building Surveys

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 and often nothing more serious than just expansion or settling, cracks in the walls of your home can be caused by one of the following: 

  • In new builds and extensions, the foundations can settle under their own weight causing slight cracks in the walls. Often these are presented as hairline cracks and become nothing serious once the house has settled in.
  • In older properties, fluctuation of the temperature and variations in humidity levels will cause the structure to sink and swell over time.
  • Newly plastered walls can often experience hairline cracks as they dry out, which is fairly common.
  • If you live on a busy road with a lot of heavy traffic, cracks in your house may be caused by road traffic vibration.
  • Timber window frames that have been replaced with uPVC double glazing units can cause cracks around the window, above or below, if a supporting lintel isn’t fitted.
What causes cracks in the walls of my home?

Do cracks indicate my property has subsidence?

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

Larger cracks can often be caused by:

  • Underground drainage damage and underground leaks will often displace the soil around the foundations.
  • 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 can cause soil movement around the foundations.
  • Prolonged dry weather – there was a 300% increase in subsidence-related claims due to the hot, dry weather experienced in July, August and September 2018, compared with the previous three months.
  • 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 move.
  • Mining – in some parts of the UK, local underground mines, including those long-disused, can cause damage to the foundations of the property.
  • 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.

How do I know what type of cracks in my house are serious?

No two cracks are the same!

Cracks vary in length, width and direction. Typically, larger cracks (those bigger than 15mm in width) are a cause for concern and should be assessed by a professional structural engineer as soon as possible.

Subsidence cracks usually appear quite suddenly, rather than slowly over time. They’re usually diagonal and wider at the top than at the bottom, and are often found around doors and windows. Lintel failure may need to be ruled out first, as these types of cracks can look similar.

Different types of cracks:

Negligible – hairline cracks less than 1mm in width. These can be easily fixed by filling the crack with a suitable filler and redecorating.

Slight – cracks between 1mm and 5mm in width, which can be fixed with filler after ruling out any structural issues such as a failed window or door lintel. You might need to repoint exterior cracks.

Moderate – cracks between 5mm and 15mm may need professional building work and there might be underlying issues that will need to be addressed in order to provide a permanent fix.

Severe – cracks up to 25mm wide could be a sign of structural damage and should be inspected and repaired by a professional Structural Engineer.

Very severe – any crack above 25mm in width indicates serious structural damage and will need major repair work, which could include underpinning and rebuilding. Subsidence cracks can be wider at the top than the bottom and are likely to be visible from outside the property as well as inside.

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. Instead of filling and repainting them straight away, you should wait a while before filling the cracks and repainting, as more could appear. If vertical cracks are wider than 0.5cm, there could be a more serious cause, which should be investigated.

Diagonal cracks – these can look, in shape, like a set of stairs going along your wall. They could be a sign of structural movement. Take them seriously. A structural engineer will often advise if the cracks are due to movement within the soil below the foundations, or the foundations themselves failing. One remedy for this issue is to recommend Helical Rods to tie the bricks either side of the crack to prevent further expansion. See illustration below.

What causes cracks in the walls of my home? 

What causes cracks in the walls of my home? – Some diagonal cracks around doors and windows can appear because the lintel above is missing, weak or badly installed. It’s best to get expert help from a Structural Engineer to determine the cause of the problem and offer a design service for a replacement beam.

What should I do if I’m worried about cracks in my property?

What causes cracks in the walls of my home?
Crack monitor which a structural engineer may install to monitor cracks over a period of time to determine if the cause is due to subsidence

If you rent your property you should talk to your landlord first and as soon as possible. Leaseholders should contact the freeholder about the problem as soon as they are able – as they’ll be responsible for rectifying the structural issues. In both cases, the owner should have buildings insurance and may make a claim on their policy. If the cracks are just in the plasterwork alone, you may be responsible for repairing these yourself, so check your lease or rental agreement.

If you own your home and you’re worried about cracks in the building – large or small – seek the help of a building professional or structural engineer as soon as possible. For a reasonable fee they will conduct an assessment of the issues and provide a report along with recommendations on how to rectify the issues.

One of the first things a structural engineer may do depending on the severity of the crack, is monitor the cracks in your home to see if any movement has now stopped, or if it’s still moving and requires further assessment. This can be a simple procedure, where some removable studs or gauges are placed either side of the crack and changes in position are monitored over time. Other times, structural engineers are able to use their experience in ascertaining what the cause of the cracks are and provide a detailed report explaining how to rectify the problem.

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 claims on the rest of your cover. 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.

But cracks caused by natural settlement, thermal movement and lintel failure will be considered a maintenance issue – and because buildings insurance doesn’t cover wear and tear or normal deterioration, you’re probably uninsured.

If the cracks are a result of subsidence caused by an escape of water, like leaky drains, your claim for loss or damage will usually be considered under the ‘escape of water’ clause of your insurance policy at first. This could have the advantage of being subject to a lower policy excess. But there may be a specific exclusion for subsidence damage under this section of the policy – in this case, you’ll have to claim under the subsidence rules, which will usually have a higher excess.

If the subsidence is due to mining, there may be a claim against the Coal Board or mine owner, for example. You’ll need to discuss with your insurance provider whether to claim from them directly, or if the provider will do it on your behalf. If in doubt, take a look at your policy document to find out exactly what’s covered or contact your insurance provider directly. If you make a subsidence claim, you’ll also need to make this clear when comparing insurance or applying for insurance in the future.

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