When should you worry about cracks in your walls?

Turning a blind eye to cracks in walls may mean you’re missing the warning signs for serious and ongoing structural damage caused by subsidence.

Cracks in walls are common in buildings; though some are nothing to worry about, others can indicate a sinking or damaged foundation (subsidence). If you don’t address problematic cracks in walls, the damage to the foundations can quickly devalue the property.

Print-at-home Crack Gauge

To help you discover if the cracks in walls around you home could be due to subsidence, we’ve developed this handy tool. Visit our crack gauge page to download our FREE crack gauge and start measuring and monitoring the wall cracks around your home now!

Print-at-home crack gauge

Cracked walls in homes

Mainmark’s level correction methods are effective for cracks in walls in buildings of any size, including residential homes. We visit your home, assess damage, and discover the cause. Our experienced engineers and technicians establish the underpinning approach needed, creating a plan specific to the needs of your house.

Houses that need to be re-levelled often develop cracks in walls, which can occur internally and externally. These houses require their foundations to be lifted and re-levelled. As the building is re-levelled wall cracks generally close up, leaving only a little cosmetic crack repair, such as patching and painting, to deal with. Most importantly, structural damage is resolved, and the future of the house is sound. Our cutting edge solutions are the modern answer to traditional concrete underpinning and are likened to keyhole surgery. Our alternatives are not just for concrete slab floors; we can raise and relevel strip footings and raft slabs, plus we can fill gaps in paths and driveways.

Types of Wall Cracks

Download our Guide to Wall Cracks and learn about the typical type of wall cracks that form in homes and why do they appear?

Guide to Wall Cracks

Step Crack

Often found on masonry walls, they appear like steps in the brickwork/blocks and typically follow mortar lines. The mortar and masonry deteriorates due to the movement of the affected wall.

 

⚠ Foundation failure due to subsidence/soil movement and moisture variations.

Horizontal Crack

Found running horizontally between bricks and in some instances, they transition to become a step crack. Internally they typically appear as gaps between the skirting board and floor or between the cornice and ceiling.

 

⚠ Subsidence, causing foundation failure beneath the problem wall.

Articulation Joint Crack (Expansion joint)

Usually visible in building extensions where two walls join and in modern buildings at the sides of large window and door openings. The gap is often wider at the top of the joint, exposing the lining.

 

⚠ Poorly compacted soil during construction of the building/extension and incomplete or inadequate foundations or footings.

Corner Crack

Buildings built using clay bricks are susceptible to cracks in corners as overtime the clay expands creating lateral force pushing against each other. The mortar around the clay brick deteriorates exposing gaps in the brickwork.

 

⚠ Moisture levels in the air causing clay bricks to expand and contract.

Vertical / Diagonal Crack

Evident in both masonry or concrete walls where the crack is wider at the top, indicating the wall settling or heaving. They are normally jagged or zig-zag and don’t follow a uniform pattern.

 

⚠ Foundation movement due to soil moisture variations or vibrations in the ground.

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What causes cracks to form in walls?

Soil Types:

Moisture levels in the soil affect loosely packed soils, sand and reactive clays as they either expand or contract or wash away.

Excess Water:

Burst or cracked water pipes including blocked sewage and rain gutters cause the ground to heave as it absorbs the moisture.

Tree Roots:

Neighbouring trees and shrubs absorb water using their roots causing movement in the soil as it soaks up moisture in the ground and grows.

Extreme & Seasonal Weather:

Natural disasters such as flooding, drought and earthquakes affect soil moisture levels in particular clay where it compresses and expands resulting in excessive foundation movement.

Footing Systems:

Flawed foundation design or inadequate compaction of soil during construction results in movement of the structure as it settles.

Renovation or Construction:

Vibration caused by nearby construction activity such as drilling or piling, or heavy road traffic causing soil particles to shift and weaken the ground.

When do wall cracks indicate a structural problem?

Larger cracks that display these characteristics may indicate weaknesses in the building’s foundation:

  • One side of the wall is higher than the other
  • Doors and windows no longer close in their frame
  • Cracks are wider than about 5 mm (or half a centimetre)

Problematic wall cracks will typically start at windows, doorways or corners of buildings. Generally, smaller hairline cracks are not cause for concern. These are usually the result of seasonal expansion and contraction of soils beneath the building over time, and can be easily patched and re-painted.

computer screen with Typical signs of subsidence

Want to learn more about the signs of subsidence?

Explore our interactive house and view typical subsidence problems around your home

Sinking floors, paths and driveway slabs, cracked walls, jamming doors and windows can all be indicators of structural damage due to subsidence and voids under the ground. Typical causes are unstable or weak ground, a broken pipe causing soil erosion, moisture changes in clay soil, nearby building and excavation works, and seismic activity or liquefaction. Our solutions are cutting edge and the modern answer to the traditional way to underpin; they are like keyhole surgery compared to concrete underpinning. Our alternatives to underpinning are not just for concrete slab floors. We can underpin, raise and re-level strip footings and raft slabs, plus we can infill under slabs and driveways.

Start Exploring

What causes large cracks in walls?

Large cracks may appear because the property’s foundation has shrunk or lost its strength, causing all or a part of a building to sink, known as subsidence. This usually happens because the moisture in the soil beneath the settled section the building is either too wet or too dry.

How to fix large cracks in walls

The best long-term solution for fixing large cracks is to lift, re-level and re-support the building. This level correction process is called underpinning. As the building is re-levelled, the cracks in walls may close or become smaller (ready to plaster or render walls for fine patching and repainting). Windows and doors will also usually begin to work properly again. Traditional underpinning or level correction methods involve excavating or digging up parts of the foundation, pouring in concrete, waiting for it to set and then jacking up the building off the concrete blocks. However, this traditional method can be time consuming (often requiring weeks or months) and messy. It usually means you’ll have to vacate part or all of the building while tradespeople work.

Mainmark’s level correction methods are much friendlier, both to the building and to those that occupy it. Our non-invasive techniques are cost and time efficient.

Various product warranties and Building Code requirements apply (please contact us to see which apply in your region or country).

Benefits of Mainmark’s level correction methods:

Cracks in walls generally close up

Jammed doors and windows are freed up

We don’t make mess: there is no concrete dust, water, or anything else to clean up

There is minimal disruption

We don’t cause further damage to the house or the landscaping

With simple jobs, residents can stay in the home and may not even need to move much furniture

Techniques are non-invasive: we don’t tear up floors or excavate ground

Many simple, residential jobs are done in a day

The methods we use strengthen weak ground, so your home becomes level, crack-free, and more stable

The products and techniques we use have no negative impact on the environment.

Mainmark level correction methods used on homes:

For expert advice on identifying the causes of movement in a building, download a copy of ‘Foundation Maintenance and Footing Performance: A Homeowner’s Guide’ from CSIRO.