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Cracked Walls


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 houses. Some are superficial and nothing to worry about. Others could indicate you have a sinking or damaged foundation (subsidence). If this sinking continues, the cracks may get wider. 

Before you carry out wall crack repairs and move on, consider whether there may be a deeper underlying issue. If you’re worried about cracks in your walls, call Mainmark to assess these before the issue worsens.

Repair cracks in bricks caused by movement

Understanding Cracked Walls: Subsidence Causes and Factors

The issue of subsidence, especially in the context of cracked walls, stems from a multitude of causes and contributing factors. All of these share a common thread—a shift in the ground, resulting in soil movement.
Moreover, the impact varies depending on the type of ground involved. When the ground undergoes changes, building subsidence becomes a prevalent concern.
In such cases, foundations or footings lose their full support and begin to sink due to the weakened ground.

Expansive Soils

A contributing factor to wall cracks is irregular soil behaviour. For example, soils containing reactive clay can expand or contract throughout the year. Rainy seasons will lead to soil expansion from moisture, while contraction occurs in the warm, dry conditions of hotter months. 

These fluctuations could be regular, or the soil may expand and contract unevenly. This causes stress to the foundations of your home, which could lead to internal and/or external wall cracks. This will be of particular concern as more parts of the country experience extreme weather events year on year.

Tree Roots

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

Poor Drainage

One major contributor to wall cracks is issues with drainage. Pipes left unconnected, broken drains and other leakages can mean water drains into the soil under your home. This erodes the soil over time, leading to ground instability. 

The soil under your home could also suffer from aeration, or voids could form. This eventually leads to ground instability, which causes wall cracks.

House Extensions

Wall cracks can appear when the weight of your home increases beyond the foundation’s capacity. Wall extensions or other extra loads increase the weight of the house, as well as increasing the force exerted on the foundation and the soil it sits on.

As with soil expansion, uneven direction or distribution of this force can put stress on the structure. Wall cracks in this case might be the start of more serious issues.

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.

Expanding Materials

Expanding materials can also cause wall cracks. Some clay bricks expand as they age, increasing up to several millimetres per year in some cases. Concrete is another material that can contract or shift over time. These changes can cause wall cracks unless properly controlled. 

Trust The Experts

Mainmark Specialises in Re-levelling Homes

Whether you can identify the cause of your wall crack or not, it is important to note that cracks are just a symptom.

If you’re worried, call Mainmark to assess your house. We can improve the ground beneath your house or carry out re-levelling to mitigate further damage.

Mainmark specialises in re-levelling buildings that have experienced structural issues, which could lead to wall cracks. We developed the Teretek and JOG technologies, which are versatile and suitable for re-levelling both simple and complex structures.

JOG is a non-invasive method of injecting cementitious grout beneath your house. This results in a supported and improved foundation.

Teretek uses a method of injecting polyurethane resin beneath your house. As the resin expands, it gently lifts the structure. This is also a non-invasive and cost-effective solution.


Mainmark’s Level Correction Methods


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.


Our solutions are of surgical nature compared to traditional methods.


Compared to traditional methods, our solutions are cost-effective, with minimal external disruption to the area.


Cracked Wall Repair in Action

Our Teretek® Resin Injection technology can raise, re-level and re-support subsiding properties.

This remarkable solution is the key to raising, re-leveling, and re-supporting properties affected by subsidence. Our skilled team of consultants and technicians will guide you through the process, demonstrating how we correct subsidence.

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!

Google Reviews

Incredible company to deal with.
Professional from beginning to end. The Mainmark team worked together to provide a service second to none and the work they did was just amazing.
Top company, top service, top team equals top result. Highly recommended.
Heather – Wellington
The team from Mainmark were great.

We are impressed and very satisfied with the Chch Mainmark team and the higher engineering staff involving lifting our house. The site foreman Ronnie and his crew were informative and customer conscious and constant monitoring any progress. Our 260m2 concrete slab with existing serious cracks and different levels responded well to the lifting and Mainmark managed to level our house. Compared to other methods Mainmark is the best in our view, considering the shorter time frame, overall lower cost and less damage control. Highly recommend Mainmark.

Josje – Christchurch

Incredible company to deal with.
Customer service is extremely helpful and answered every question with either an answer or a solution even often both. The on site team are second to none, perfect people to have work on and around your home, time efficiently spent and extremely neat site work. Would highly recommend and encourage everyone to use this company.

Jared – Auckland 


Frequently Asked Questions

For Personalised Answers Please Complete The Form Below

We’ve compiled answers to some of the most common queries our customers have. We strive to provide you with clear and informative responses to help address your concerns.

However, we understand that your situation may be unique, and you might have specific questions not covered here. Our dedicated customer service team is ready to assist you further. If you can’t find the information you’re looking for in our FAQ, please don’t hesitate to contact us. We’re here to ensure you have all the support and guidance you need. Feel free to reach out to us now with your specific inquiry, and we’ll be more than happy to assist you.

How do you know if a wall crack is serious?

To determine the seriousness of a wall crack, look for the following signs that may indicate a significant problem with the structural integrity of your home, potentially requiring foundation repair work, including underpinning and rebuilding:

  • Width: Any crack wider than 5mm is a strong indicator of an issue.
  • Shape: Cracks that are wider at the top than the bottom, or those visible from the external walls, can suggest subsidence.

These are crucial indicators that should prompt you to seek professional advice and assessment from Mainmark for a potential solution.

Should I Be Concerned About Wall Cracks?
  • Cracks measuring less than 5 millimeters in width are typically confined to the plaster and can be easily repaired and concealed.
  • Cracks spanning between 5mm and 15mm in width may indicate more significant structural issues and may necessitate professional repairs.
  • Any crack exceeding 25mm in width should be thoroughly inspected by a professional.

Mainmark offers complimentary inspections. If you have concerns about cracks in your walls, please fill out the form, and we will take care of the rest. Your peace of mind is our priority.

How do you know if internal cracks are structural?

Recognising Signs of Structural Cracks in Your Foundation:

  • Step cracks.
  • Cracks on foundation slabs or beams.
  • Vertical cracks that exhibit varying widths, typically wider at the bottom or top.

If you’re uncertain about the nature of your internal cracks, Mainmark is here to assist you. Contact us for expert guidance and a free assessment.

What is an example of a structural crack?

Structural cracks often come with clear indicators that set them apart from cosmetic cracks. Here are some common signs of structural cracks to look out for:

  1. Step/raise in your floor: If you notice that your floors are no longer level and exhibit a noticeable raised area, it can be an indication of a structural issue.
  2. Various Shapes and Sizes: Structural cracks are diverse in appearance, ranging from horizontal, vertical, and diagonal lines to those resembling a staircase pattern within foundation blocks.

If you suspect structural issues in your property, please call us for an assessment.

How much does it cost to repair wall cracks?

If you have cracks in the wall the cost of remediation can vary depending on the specific circumstances of your foundation. To provide an accurate estimate, we recommend scheduling a free site inspection with one of our experts. They will assess the damage and provide you with a customised quote based on your unique situation.

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 and assess the damage. They will establish the approach needed, create a plan specific to the needs of your building and provide you with a detailed quote.

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Mainmark Ground Engineering (NZ) Ltd





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