How Do I Know If Wall Cracks Are Serious or Just Cosmetic?

However, some serious wall cracks can indicate a deeper issue, such as foundation movement, subsidence, weak soils, voids beneath the slab or uneven settlement. These cracks are more likely to appear suddenly, widen over time, return after being repaired, or appear alongside other warning signs such as sticking doors, jammed windows, uneven floors or gaps around skirting boards.

So, how do you tell the difference?

The key is to look at the size, shape, location, pattern and progression of the cracks, not just the crack itself.

If you are unsure whether cracks in walls are cosmetic or structural, it is worth arranging an expert site assessment before carrying out cosmetic repairs. Patching and painting a crack may improve the appearance, but it will not address foundation movement if the ground beneath the home is still shifting.

What are cosmetic wall cracks?

Cosmetic wall cracks are usually fine, shallow and stable. They often affect plaster or paint only and are not usually linked to foundation movement.

What are serious wall cracks?

Serious wall cracks are cracks that are widening, changing, stepped, diagonal, or appearing with other symptoms such as sticking doors, uneven floors or cracks around windows and doors.

You should pay closer attention to wall cracks if they are changing, spreading or appearing in a pattern that suggests movement.

Warning signs that wall cracks may be serious

Arrange an expert assessment if you notice:

• Cracks that are getting wider or longer
• Cracks that return after being patched
• Stair-step cracks in brickwork or blockwork
• Diagonal wall cracks from the corners of windows or doors
• Cracks around windows and doors
• Cracks that are wider at one end than the other
• Horizontal cracks in brick or masonry walls
• Cracks visible on both internal and external walls
• Gaps between walls, ceilings, floors or skirting boards
• Doors or windows that stick, jam or no longer close properly
• Sloping, uneven or sinking floors
• Cracked floor tiles
• Separation between the house and paths, patios or extensions
• Sunken concrete slabs, driveways or verandahs
• New cracks appearing after heavy rain, drought or drainage problems

One crack by itself does not always mean there is a major issue. But a crack combined with movement symptoms is a stronger sign that the foundations or supporting ground may need investigation.

Cracks around windows and doors can be more concerning than random hairline plaster cracks because openings are natural weak points in a wall. When a house moves unevenly, stress often appears at the corners of windows and door frames.

Look carefully at the direction of the crack.

A fine, stable plaster crack near a window may be cosmetic. But a diagonal crack running from the corner of a window or door, especially if it is widening or visible externally, may indicate foundation movement or uneven settlement.

Question homeowners often ask:
“Why are cracks appearing around my window frames?”

A likely reason is that movement is placing stress around the opening. This may be caused by normal building movement, but it can also be linked to subsidence, weak soils or foundation settlement.

Stair-step cracks are cracks that follow the mortar joints in brickwork or blockwork. They often appear in a stepped pattern, particularly on external brick walls.

These cracks should not be ignored, especially if they are widening, recurring or appearing near corners, windows, doors or extensions.

Stair-step cracks can be one of the visible signs of foundation movement because they may indicate that one section of the wall or footing is moving differently to another.

Diagonal wall cracks can be more concerning than fine vertical plaster cracks, particularly when they extend from the corner of a window, door or opening.

Diagonal cracks may suggest differential movement, which means one part of the home is settling or shifting at a different rate to another part.

A diagonal crack does not automatically mean your home is unsafe. But if it is widening, reappearing after repair, or matched by external brick cracks, uneven floors or jammed doors, it is time to arrange a site assessment.

Some wall cracks can be monitored before taking further action. Others should be assessed sooner.

Monitor the crack if:

• It is very fine and hairline
• It appears only in plaster or paint
• It has not changed over time
• There are no external cracks nearby
• Doors and windows still operate normally
• Floors feel level and supported
• The crack does not return after minor cosmetic repair

Take clear photos, record the date and measure the crack width. Check it again after heavy rain, dry weather and seasonal changes.

Arrange an expert site assessment if:

• The crack is widening or spreading
• The crack has appeared suddenly
• The crack is diagonal, stepped or horizontal
• Cracks are visible internally and externally
• Doors or windows are sticking or jamming
• Floors are sloping, sinking or uneven
• Cracks keep returning after being repaired
• You are buying, selling or renovating the property
• You suspect subsidence or foundation movement

If a wall crack is cosmetic, patching and painting may be all that is needed.

But if the crack is caused by foundation movement, patching the wall only treats the visible symptom. The crack may return because the ground or foundation issue has not been addressed.

This is why Mainmark focuses on understanding the cause of the movement. A site assessment can help identify whether the issue is related to weak ground, voids, subsidence, slab settlement, poor drainage or another factor.

Once the cause is better understood, the right repair approach can be considered.

Mainmark has provided ground engineering and foundation repair solutions since 1989, helping Australian homeowners address issues caused by ground movement, subsidence, weak or reactive soils, voids and foundation settlement.

For homes showing signs of foundation movement, Mainmark may recommend solutions such as:

• Foundation repair
• House re-levelling
• Ground improvement
• Void filling
• Resin injection
• Slab lifting
• Underpinning alternatives
• Structural support solutions

The right solution depends on the property, soil conditions, footing type, access, severity of movement and the cause of the cracking.

Mainmark’s resin injection solutions are designed to improve ground conditions beneath affected areas. In suitable situations, expanding resin can be injected through small holes to fill voids, improve support and help re-level parts of a structure.

This approach may reduce the need for disruptive excavation or traditional underpinning, depending on site conditions.

Where foundation movement has caused part of a home to sink or become uneven, house re-levelling may help lift and re-support affected areas.

This can help address related symptoms such as cracks in walls, uneven floors, jammed doors and windows, and sinking slabs.

A Mainmark site assessment helps determine what may be causing the cracks and whether they are likely to be cosmetic or linked to foundation movement.

During an assessment, the team may look at:

• Crack patterns and locations
• Internal and external symptoms
• Floor levels
• Doors and windows
• Drainage and moisture conditions
• Nearby trees and vegetation
• Slabs, paths, patios and driveways
• Signs of subsidence or settlement

The goal is to understand the cause before recommending a repair method.

1. Take photos of the cracks.
2. Note when you first noticed them.
3. Measure the width if possible.
4. Check whether they are changing.
5. Look for cracks outside in the same area.
6. Test nearby doors and windows.
7. Check floors for unevenness or sinking.
8. Look for drainage issues, leaking pipes or pooling water.
9. Avoid major cosmetic repairs until the cause is understood.
10. Book a professional assessment if the cracks are growing or linked to other movement signs.

If you have noticed serious wall cracks, cracks around windows and doors, stair-step cracks, diagonal wall cracks, sinking floors or signs of foundation movement, Mainmark can help you understand what may be happening beneath your home.

Book a Mainmark site assessment to identify the likely cause of the cracking and discuss suitable foundation repair, ground improvement or house re-levelling options for your property.