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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.

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.

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.

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.

Likely causes:

Drought drying out soil, especially soils containing reactive clay

Shrinking clay

Liquefaction caused by earth movement and earthquakes

Washaways from broken pipes


Poorly compacted fill

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.