Cracks in Walls: When to Worry UK
Cracks in your walls can be a minor, aesthetic issue, owing to old paintwork or dry plaster - but it can also be an indication of serious problems with your foundations. The key thing to watch out for is cracks over 0.5 cm wide, or that keep on growing!
Here we'll explain some of the primary causes of cracks in walls and the signs you need to carry out urgent repairs.
Factors That Cause Cracks in Walls
Seeing tiny hairline cracks appearing in your home can be frustrating, especially if you've not long finished redecorating.
There are thousands of reasons this might happen, and a lot of the time, cracks are a regular part of wear and tear.
Minor Reasons for Cracks to Appear
Some of the causes of cracks in internal walls include:
- Sudden temperature changes.
- Fluctuations in humidity.
- Vibrations - common near busy roads.
- Dried out plaster or old paintwork.
- Faulty taping between plasterboard panels.
- Natural movement above door frames.
However, if you're seeing signs that cracks keep appearing, run diagonally across walls, or are over 0.5 cm wide, then it could be something more suspicious.
Serious Causes of Cracks in Walls
More troublesome scenarios could be:
- Damp, where the framing and plasterboard are becoming saturated.
- Tree roots growing under your property.
- Subsidence and deteriorating foundations.
It's therefore key to understand why cracks in walls appear and spot the red flags that you have a structural issue that needs immediate attention.
Most minor issues appear on the ground floor, where the walls bear the weight of upper levels, so if cracks begin to show upstairs, it may also require further examination.
Other Considerations That May Impact the Walls in Your Home
It's rarely obvious what has caused a crack until you investigate - but some properties are more susceptible.
Factors such as the age of your property can be a cause. New homes built with timber framing or timber stud work can develop cracks fairly quickly.
That happens because the more recent (or green) wood contains higher moisture levels. As the wood dries out, it moves in tiny increments, which can result in small cracks.
The best solution in this situation is to wait until the home is about one year old - any repair work before then will probably have to be repeated.
Older period homes are also more prone to cracks in the walls, usually because the plaster has begun to break down, and needs replacing.
Issues such as cracks over doors and windows are typical, where the property has settled and shifted just slightly.
Most walls contain vertical studs, running from the floor to the ceiling. When those studs are cut to add a door or window, the joins will always be very slightly weaker - and so as the house settles, hairline cracks can develop.
Again, these aren't severe structural problems and can be remedied with re-taping the plasterboard, re-skimming the wall, and painting or wallpapering as normal.
Therefore, if you're looking into the causes of cracks in your walls, it's worth thinking about:
- Whether the home is a new build.
- How the property has been constructed.
- What sort of stud work sits behind your walls.
- Whether it's a period home.
- Where the cracks are occurring.
Vacant properties are also exposed to cracks, as when the home is occupied again and the heating kicks in, the temperature changes quickly cause the frames to expand and contract.
How to Spot a Dangerous Crack in a Wall
So, now we've run through a range of scenarios and potential causes, let's examine the situations when you have reason to worry and need to take quick action.
Cracks that are jagged (rather than in a straight line) or running on the diagonal can be a warning that the foundations have shifted or shrunk.
It might also be due to woodworm or other termites.
These pests cause a huge amount of damage to wood and timbers, including supporting joists (depending on the property's age) and mean that wood begins to deteriorate or even collapse.
If the cracks in your walls meet any of the below criteria, it's time to call a builder.
- Wider than 0.5 cm
- Growing in length or width
- Daylight is visible through the crack
- Jagged in shape
- Running diagonally across a wall
- Cracks appear in multiple rooms
- Damage is visible on the inside and outside.
Note that this doesn't automatically mean that you need repairs to your foundations or extensive work - but it's critical you consult a contractor, structural engineer or surveyor to highlight the cause before it gets worse.
How to Fix Cracks in Internal Walls
The best way to fix a crack in a wall depends on the reason for the damage.
If it's a simple decorative problem, for example, in a new building that's shifted since you moved in, you've got a much simpler task than if the cause is structural.
Repairing a Crack in a New Build Wall
It's normal for new build properties to settle over the first year or so, so you can repair most minor cracks without the need for a professional builder.
The best method is to ensure any dust is removed and then take back any crumbly plaster until you're on solid ground.
A standard crack filler or mortar mix will fill the crack, and then you can either sand back so it's level with the wall or have the whole section re-skimmed (a plasterer applies a very thin layer of plaster).
When it's fully dry, you can repaint or wallpaper as you wish.
Fixing Wall Cracks in Vacant Properties
Homes that have been empty for a while often experience small hairline cracks, which is a common side effect of changes to the heat and humidity in the air.
Again, it's best to hold fire until the property is in regular usage, and then you can either fill the crack with filler or re-tape the joints between plasterboard panels.
Rectifying Faulty Plasterboard Construction
In some cases, cracks appear because the quality of the work isn't up to scratch. Unfortunately, it's not unheard of for walls to crack because of:
- Badly applied plaster.
- Walls being decorated before the plaster has completely dried.
- Poor quality lintels and support beams for doors and windows.
- Low standard fixings.
If you discover that your wall cracks have appeared due to bad building work, you might be able to get the original contractor to come back and fix the damage, especially if it's a new development and you have time to compile a snag list.
Otherwise, you can usually scrape back the paint, re-tape the plasterboard, fill any cracks, and then paint over the top - it's well worth taking the time to go back to the base layer since painting over won't stop the crack from reappearing in a few weeks.
How to Fix Wall Cracks Caused By Water Damage
Water damage can be a real hazard for homes, and if you've got wall cracks due to dampness, the first step is to address the problem.
Whether that's a leaking pipe, rising damp or a roof that isn't watertight, there's little point in spending time and effort on repairing your walls if the water ingress hasn't been sorted.
Once you are confident that the leak has been fixed, you'll need to give the damaged area of your walls a very thorough clean, scraping back any flaking paint and stripping off damp wallpaper.
Painting over the top won't do the trick since water stains are persistent and will seep back through, so it's vital you remove any damp plasterboard and paint and allow it to dry out thoroughly.
Next, you can use a sealer or binder to prevent stains from returning, fill your crack, sand it back, and apply primer and paint.
Paint won't sit properly on surfaces with even the slightest hint of damp (you'll get bubbles or more cracks), so take your time and make sure the wall is ready for redecorating.
Addressing Cracks in Walls Due to Foundation Issues
If you've got a more serious issue with your foundations, a lot will depend on your builder's recommendations or the advice given by a structural engineer.
Some of the solutions can include:
- Underpinning the property, whereby a contractor reinforces the foundations using a range of techniques depending on the age and construction of your home.
- Filling cracks in foundation walls with epoxy or sealant as a permanent seal.
- Strengthening soil under your property, using grouting or resin to shore up weakened earth.
- Installing screw piles and brackets, often where the excavation under your home is deeper - these piles then support the foundations from underneath.
- Mass pour concrete involves digging cavities under the foundations and filling them in with concrete. This method is most suited to homes with shallow foundations.
Only when the foundations have been fixed can you look at repairing the cracks - they'll continue to appear as long as the property's foundation isn't stable.
Larger cracks normally need to be fixed by a contractor, again often using epoxy or sealant.
Severe cracks, especially those reaching external walls, may require replacement brickwork or even whole walls to be demolished and rebuilt if a builder can't repair the damage.
Benefits to Seeking Professional Advice to Repair Wall Cracks
If you doubt the reason for cracks in your walls, it's crucial to have the damage inspected by a professional. Cracks over 0.5 cm wide are often caused by structural deterioration.
Very large cracks are usually an indicator that you will need underpinning and rebuilding work, so it's never wise to repair the crack without identifying the underlying issue.
Even if your wall cracks turn out to be purely decorative, any subsidence issues can be a huge issue if you come to sell your property. It may save considerable time and money to ensure you've had wall cracks correctly diagnosed.
Small cracks can, of course, be repaired without expert support, usually with wall filler, sandpaper and a new coat of paint, but only when the reason is not structural.
You must seek professional contractor advice or commission a structural engineer to conduct a full survey where you suspect a problem with the foundations.
Foundation damage can be a considerable safety hazard and may even mean the property is unsellable in the future, so it's essential to have the problem resolved.
FAQs - When to Worry About Cracks in Walls UK
Here we'll run through some of the most commonly asked questions about when you should start worrying about cracks appearing in your walls.
Do Walls Normally Crack on Their Own?
Yes, internal walls in properties often crack, which is a surface repair rather than anything impacting the brickwork behind.
This damage is usually due to natural settling and changes to the property's temperature, making stud work and wooden batons behind your plaster expand and contract over time.
How Do I Fix a Crack in a Wall?
The right way to fix a wall crack depends on the cause of the damage. You can easily repair minor cracks with filler, but if you want a perfectly flush finish, you might wish to appoint a decorator or builder.
You can also rectify deeper hairline cracks with filler, but it's best to scrape back the paint and sand the whole wall to ensure you don't end up with bumps or ridges.
Finally, an appropriately qualified builder should always repair serious cracks and those that indicate a bigger problem.
Large gaps in walls can cause the structure to sag or even make a wall unstable, so a contractor must repair this properly.
Do I Need a Professional Contractor to Fix a Wall Crack?
If you have a large crack in your wall or damage to a load-bearing wall, it's advisable to commission a structural engineer to recommend the best way to repair the crack.
Wall cracks are common in both new buildings and older homes and often result from settling, whereby you can repair the damage to the wall, fill the gap and decorate over the top.
However, it's essential you know the cause behind cracks in your walls since this will impact the correct repair method and any other required repair works.
What Causes Cracks in Walls?
Wall cracks appear for hundreds of reasons, ranging from serious structural problems to natural changes over time.
Some of the common causes are:
- Settling: when homes are built, excavations naturally mean that the soil underneath has been disturbed. As it compacts and settles over time, it can mean that walls crack inside, over months or even years. You can spot this type of wall crack by looking for vertical cracks.
- Subsidence: significant downward motion underneath the house, or subsidence, can be a much bigger issue. Soil movements where the earth slips underneath or the foundations become unstable can cause a property to collapse, so repairs are crucial.
- Soil types: some areas have higher clay content in the soil, called reactive soil, which expands more dramatically when it gets damp. Sand and gravel are non-reactive, so far less likely to cause wall cracks.
- Temperatures: changes to temperature, damp and even bad weather can affect the water table in the ground far below and end up with cracks appearing in your walls.
- Local impacts: if you live near a busy motorway or construction works, the vibrations may cause walls to crack. This situation can also happen to properties close to quarries, where sandblasting produces vibrations throughout the local area.
- Poor craftsmanship: inadequate design can put too much weight on load-bearing walls, causing them to crack. Low-quality materials or badly engineered layouts can also result in cracks appearing.
- Water damage: anything from blocked gutters to leaking pipes can filter through to your walls, impacting the internal wall's robustness and saturating soil underneath your foundations.
How Much Does it Cost to Fix a Crack in a Wall?
Costs vary depending on how extensive the repair work is, but as a rough indication:
- Re-plastering a small room costs around £600 to £700.
- Plastering a large room can cost about £1,000 to £1,400.
- Skimming a plaster room usually costs £150 to £200 per wall.
- Plastering over a minor crack is around £125 per job.
Will My Buildings Insurance Cover the Cost of Repairing a Cracked Wall?
Most buildings insurance will cover the cost of repairs to your property caused by subsidence - provided this wasn't identified on the original survey and excluded from your policy.
It's important to check your policy and any exclusions since some insurance providers may have a cap on the maximum claim value.
If you have pre-existing subsidence, you may need to pay an additional cost for your insurance premium or pay a higher excess.
Once structural work is complete, your builder or surveyor will issue a certification confirming that the property is structurally adequate - although note that instances of subsidence may bump up the cost of your policy in the future.
References:
- https://www.localsurveyorsdirect.co.uk/what-underpinning-and-what-it
- https://www.teambuildconstruction.co.uk/wall-crack-advice/
- https://melaniesfabfinds.co.uk/household/cracks-in-your-walls-should-you-be-worried/
- https://www.thisismoney.co.uk/money/experts/article-3088418/ASK-TONY-house-cracks-insurance-costs-soared.html
- https://www.checkatrade.com/blog/cost-guides/cost-repair-hole-drywall/
- https://actioninspections.com.au/what-causes-cracks-in-walls-action-property-inspections/
- https://peekbrotherspainting.com/exterior-house-painting/here-is-what-causes-hairline-cracks-in-paint-and-how-to-fix-it/
- https://edensstructural.com/6-most-likely-reasons-youre-seeing-cracks-in-your-walls/
- https://www.bobvila.com/articles/cracks-in-walls/
- https://www.ageco.co.uk/viewpoint/insurance/when-is-a-crack-in-a-wall-serious/
By Johnny Fuller
Home Improvement editor at NWrenovations.com
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