Article: published on 24 August 2026
Presenter Nick Knowles
Cracks in walls: When should you be concerned?
- Published
Cracks in walls can appear for different reasons, from drying plaster to movement in the ground beneath your home.
Presenter Nick Knowles joined BBC Morning Live to explain which cracks you may be able to repair yourself, and when it is time to ask for professional advice.
Why do cracks appear?
Cracks can appear for several reasons, and the weather can play a part. Dry conditions can affect the ground around a property, especially where trees are taking water from the soil.
Cutting down a tree can also change the moisture levels in the ground. If there is no longer a tree taking up water, the ground can become wetter, which can also lead to movement.
Cracks can also be linked to subsidence, where the ground beneath a property sinks and affects its foundations. Not every crack means there is a serious problem, but the direction, width and location of the crack can help you work out whether you need advice.
What do vertical cracks mean?
Vertical cracks often run from top to bottom. In a newer home or extension, they can be caused by normal settling after construction.
When foundations are laid, soil is disturbed. Once the building is complete, the weight of the property compresses the ground beneath it, and this movement can sometimes cause small cracks in plasterboard.
Damp can also cause plasterboard to expand, warp and shrink again as it dries, leaving cracks behind. Plasterboard is not usually structurally important, so small cracks in plasterboard can often be cosmetic, though they may still need repairing.
Can you fix small cracks yourself?
If a crack is narrow, not growing and appears to be cosmetic, you may be able to repair it yourself.
One way to check is to mark the wall beside the crack and measure it with a ruler. Check again after a couple of weeks, then repeat the process after another couple of weeks. If it is not changing, it is less likely to be a sign of ongoing movement.
To repair a small crack, remove loose material, rubble and dust, then brush out the crack. Apply a fast-setting filler, overfill the gap slightly, scrape it flat, sand it smooth and repaint.
Your home insurance provider may be able to help if cracks are linked to subsidence.
What if the crack is bigger?
Larger cracks may need professional help, especially if they are getting wider or appearing in brickwork as well as plaster.
One repair method is called crack stitching. This involves fitting metal bars across cracks in masonry and securing them with grout to help reconnect and stabilise the wall.
Crack stitching is a job for a professional builder or specialist contractor, rather than a quick DIY repair.
Are diagonal cracks more serious?
Diagonal cracks can be more concerning, especially if they are growing, appearing near windows or doors, or continuing through the brickwork outside.
They can suggest movement in the building, including possible subsidence or a lack of support beneath part of the house. If a corner of the building appears to be pulling away from the rest of the property, you should get professional advice.
You may need checks on drains, a ground survey, or an assessment by a structural engineer. If you live in a terrace or adjoining property, movement can affect neighbouring homes too, so it is also worth speaking to your neighbours before major work begins.
What about cracks above windows or doors?
Cracks above windows or doors can also be a warning sign because windows and doors usually have a lintel above them. This supports the weight of the wall above the opening.
If the lintel is missing, damaged or not supporting the wall properly, you may see cracks above the window or door. Other signs can include bowing brickwork, a ceiling line pulling away, or wallpaper creasing.
Repairs may involve removing the window or door and adding proper support above it. This should be assessed and repaired by a suitable professional.
Can home insurance help?
Your home insurance provider may be able to help if cracks are linked to subsidence.
Cover varies between policies, so check what your buildings insurance includes and what excess applies. Cover for other causes of cracks, such as damp, can also vary, so speak to your insurer if you are unsure.
Where should you go for advice?
If you are concerned about a crack, speak to a trusted builder or a structural engineer.
A builder may be able to tell you whether the issue is likely to be cosmetic or whether it needs further investigation. For more serious cracks, a structural engineer can assess the property and advise what needs to happen next.
Word of mouth can also help when looking for a tradesperson. Ask friends, family or neighbours if they have used someone they would recommend.
