Dealing with cracks in your home


This August has been one of the hottest months on record, with a stretch of dry days that saw the mercury rising above 36 degrees in parts of the country.

While warm weather can be a blessing for sun worshippers, it also brings with it a range of potential problems for our homes - some of which can be very serious indeed.

Cracks and hot weather

Cracks are an issue that all homeowner’s dread spotting, and unfortunately, hot weather can play a significant role in causing cracks to appear and spread.

High temperatures can contribute to cracking in multiple ways, both by causing masonry and other materials to expand, and by causing the ground to dry up, which often leads to subsidence and shifting buildings.

Add to this the impact of nearby trees, which can have extensive root systems and in dry weather can suck up a huge amount of water from the surrounding ground, and it’s a perfect storm for cracks to appear.

Wet weather is bad too...

If that wasn’t enough, wet weather can have an impact too - heavy rain and flooding can saturate the ground and cause movement, especially in areas with clay-heavy soil. Leaking pipes under the ground can also cause the earth to shift, leading to movement in your home.

While spotting a crack will no doubt make your heart sink, it doesn’t always mean disaster for your home, or your wallet. We spoke to some structural engineers to find out what you should look out for, and what to do if you spot one.


All homes move

It’s important to remember that cracking happens in nearly all properties to some extent. Our homes are a combination of dozens of different types of materials, all of which expand and contract in different temperatures and humidities.

On top of that, they are all subjected to elements like rain, wind, vibrations from vehicles, nearby building work, and even earthquakes - they might be small enough that we don’t notice them, but there’s every chance your house can.


Recently-built homes in particular take time to “settle” as the ground bears the weight of the building. Essentially, our homes are always moving imperceptibly, however strong and sturdy they appear, and cracks are a natural result of that.

However, it’s important to keep an eye on any cracks that do appear to make sure that they’re not a sign of significant damage, or a first step to more damage in future. Some cracks appear and get bigger quickly, some appear then stay that way for years or even decades, and some are cyclical, growing and shrinking with the seasons.

Monitoring is key

In some cases structural engineers might use methods like affixing a small plate of glass over the crack and seeing if the glass breaks over time, but you know your home better than anyone, so stay alert and contact an engineer as soon as you’re worried.

As one engineer told us:

“It’s a matter of staying alert and being sensible. With these kinds of things, it’s better to be safe than sorry. With so many different potential causes it’s better to put your mind at ease and treat anything early rather than leave it too late.”


Types of crack

Cracks come in all shapes and sizes. The most common kind of cracks that afflict our homes are fine, hairline cracks that can often appear on our internal walls, usually running across the centre of the wall in any direction.


Typically, this is due to changes in temperature and humidity causing the plaster to dry and crack. If you knock on the plaster and find a hollow sounds, it may indicate that it's blown, and come away from the wall underneath.

While it is always worth monitoring to make sure the problem doesn’t get worse - anything over 0.5mm is bigger than a hairline crack and worth investigating - it’s typically just a cosmetic issue, and be covered by a painter and decorator.

External cracks are likely to be more noticeable, and more worrisome. Cracks can go in different directions across your brickwork, and indicate different kinds of issues, though they are often related.

What direction does your crack go?

  • Horizontal cracks will often be low down and suggest there is too much pressure from soil against the wall.

  • Vertical cracks can often result from a failure of wall ties, metal bars which hold the two separate leaves of cavity walls together - if they corrode they can expand and put pressure on the brickwork, causing cracks that stretch to meet at the intervals where the ties are places, often six courses apart.

  • Diagonal cracks are a typical sign of subsidence. Any cracks that appear suddenly and are larger than a couple of millimeters should be investigated straight away.


Subsidence cracks

An engineer told us:

“Subsidence is one of the most common reasons for cracks appearing on walls. Typically you’d see a diagonal crack running across the face of a wall, often in a stepped pattern running through the mortar, though in some cases it can go through individual bricks too.

"The diagonal pattern is due to one part of the building sinking below the level of the other, putting pressure on the wall and pulling it in different directions.”

Subsidence cracks tend to occur suddenly, and the recent weather is a key factor in their occurrence. While in some cases the impact will be minor and a brickwork specialist will be able to repoint the crack, often there will be underlying work that needs to be done to secure the structure.



While repointing can cover the actual crack - which is necessary for making the home weather proof again and to stop moisture getting into the wall and causing further damage - sometimes more work is needed to fix the underlying issue. Finding the cause is key to establishing what needs to be done.


In serious cases, groundworkers can dig out the foundations and pump in concrete to shore up the ground, levelling out the area where subsidence has occurred.

Stitch bars

Other methods include literally stitching the wall back together, digging out the mortar and inserting helical metal bars which stretch across the crack, to hold both sides together, reinforcing the wall and taking the strain of the split.

According to one engineer:

“There are a whole range of solutions that can fix the root of the issue and make the structure as good as it was before, but it’s important to make sure you deal with the actual problem, and not just cover up the issue cosmetically.”

It is worth remembering that even serious problems can usually be rectified by an experienced engineer and talented tradespeople.


Speak to an expert

There isn’t a lot of one size fits all advice for cracks. One engineer we spoke to compared cracks to headaches:

“Asking why your home has a crack is like asking why you have a headache - it could be for any number of reasons, and it could be nothing, or it could be serious. Every case is unique, and if you’re concerned, you need to speak to a structural engineer to try and find the cause and see what the best solution might be.”

Many of the architectural designers on MyBuilder will also have qualifications as structural engineers and be able to give advice, while experienced builders will also be able to refer you to structural engineers who can diagnose your issues.

The Institution of Structural Engineers is the membership body for structural engineers, and is a good starting point for finding engineers near you.

1 Comment

  1. Very helpful.

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