1800 623 312
Australia
Cracked walls
What cracks to worry about ?
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.
Now that you know what you’re dealing with, you need to understand whether these cracks indicate a structural problem.
Small, hairline cracks are not usually concerning, These are often the result of seasonable expansion and contraction of soils beneath a structure’s foundation.
However, if when you measured the cracks they displayed the following characteristics, it may indicate weakness in your property’s foundation:
- Large cracks that start at windows, doorways or corners of buildings.
- Cracks are wider than 5mm.
- Cracks are jagged, horizontal or vertical, zig-zagged, stepped in brickwork or follow mortar lines.
Identifying subsidence
Subsidence is not without warning signs. Some of the most common include:
Internal cracked walls
Wall cracks are common in homes and are often the first sign of foundation subsidence. Inside the house, they appear like steps in the brickwork/blocks or tiles and typically follow mortar or grout lines. The mortar and masonry deteriorates over time due to the movement of the affected wall.
Sinking floors
A concrete floor slab within a home can sink due to weak ground or subsidence. A building can sink at various localised points or can be spread across the entire footprint of the house foundation.
Jammed doors
Doors that don’t open smoothly, have uneven gaps or rub against frames are often a first indication of foundation damage
Exterior cracked walls
Step wall cracks are common in homes and are often the first sign of foundation subsidence. The mortar and masonry deteriorate over time due to the movement of the affected wall. Wall cracks are usually of concern when one side of the wall is higher than the other or cracks are wider than about 5mm.
Sinking & uneven concrete slabs
Sinking and uneven concrete driveways or path slabs can be an indication of unstable ground due to voids beneath the surface. If there is noticeable soil building up around slab joints, the concrete slab can start to crack around the edges as weight is exerted where there is no ground support.
Articulation joints
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.
Start measuring wall cracks from the convenience of your home.
If you notice wall cracks around your home that are:
Large cracks that start at windows, doorways or corners of buildings
Cracks wider than 5mm
Jagged, horizontal or vertical, zig-zagged, stepped in brickwork or follow mortar line
These characteristics may indicate weakness in your property’s foundation.
To help you discover if the cracks in walls around you home could be due to subsidence, we’ve developed this handy tool. Download our FREE crack gauge and start measuring and monitoring the wall cracks around your home now!
Benefits & Features
Mainmark’s Technologies & Solutions are:
Fast
Our technologies have fast curing times and treated areas can be used immediately or without the delays compared to traditional repair methods.
Environmentally Inert
Our technologies use an inert material that is non-toxic and does not leach into the environment or affect the treated area.
Non-Invasive
Our solutions are of surgical nature compared to traditional methods.
Cost-Effective
Compared to traditional methods, our solutions are more cost-effective, with minimal disruption to the area.
What causes cracks to form in walls?
There are many different causes of subsidence and various contributing factors.
All involve some change in the ground, which, in turn, generates movement of the soil.
As well, different types of ground are more affected by different conditions.
When ground has been affected, building subsidence is common. Foundations or footings are no longer fully supported, sinking due to weak ground.
Soil Types
Moisture levels in the soil affect reactive clays as they expand and contract.
Oversaturated clays lose their strength resulting in footing subsidence. In loosely packed soils, such as sand and silt, the fine particales in the soil can wash away causing the footing to settle.
Tree Roots
Neighbouring trees and shrubs absorb water using their roots causing movement in the soil as it soaks up moisture in the ground.
Footing Systems
Poor foundation design or inadequate compaction of soil during construction results in movement of the structure as it settles.
Excess Water
Burst or cracked water pipes including blocked sewage and rain gutters can oversaturate clay soils or wash fine particles from sand and silt soils and cause footings to subside.
Extreme or Seasonal Weather
Natural disasters such as flooding, drought and earthquakes affect soil moisture levels in particular clay resulting in excessive foundation movement.
Renovation or Construction
Vibration caused by nearby construction activity such as drilling or piling, or heavy road traffic causes soil particles to shift and settle, resulting in ground subsidence.
Mainmark also provide the following in Australia: wall crack repairs, sinking floor repair, Concrete slab repair, sinking foundation repair, underpinning, ground improvement, re-levelling, subsidence repair, void filling and slab lifting
Get a quote
Arrange a site assessment in 3 simple steps:
Step 1
Submit your enquiry using our online form. Include a brief message about the type of foundation issues you are experiencing.
Step 2
Our friendly customer service team will be in touch to schedule a site assessment that suits you.
Step 3
One of the Mainmark experts will visit your home or property, assess the damage, and ascertain the likely cause. They will establish the approach needed, creating a plan specific to the needs of your building and provide you with a detailed quote.
© 2026 The Mainmark group of companies. ‘Mainmark®’, ‘Terefil®’, ‘Terefirm®’ and ‘Teretek®’ are trademarks of the Mainmark group of companies.
Mainmark Ground Engineering Pty Ltd
ABN: 51 606 182 503
