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Project Profile Z15 Y036

Teretek® Used to Re-level Department Store Floors

Office Building
Earthquake induced differential settlement
Christchurch, NZ
Ground Improvement
JOG Computer-Controlled Grouting

Teretek® Used to Re-level Department Store Floors


Farmers Trading Company (Farmers) is one of New Zealand’s largest department store chains. Following humble beginnings in 1909 as a mail order company, the business now has 58 stores across New Zealand, including one in Whangarei.

The Whangarei store had experienced significant differential floor settlement due to underlying soil subsidence over time. The store is located in a commercial neighbourhood built on reclaimed land and underlying marine silts, and the building had become unsafe due to undulating floor levels.

The 100-150mm thick concrete floor slabs had sunk unevenly across more than 800m² of retail space. In many areas, the settled floor bays had ‘hung up’ around piled pad footings. In some areas, the floor had sunk as deep as 76mm.

The subsidence had also caused the retail store’s shelves to become un-level, compromising the safe display of merchandise, while the ground was a trip hazard for customers and employees.

The store was about to be redeveloped, so it was important to first re-level the floor to allow the rest of the redevelopment to be carried out safely and effectively.

Mainmark was appointed to re-level the floor in this iconic retail space so that the additional works could take place. Mainmark used its proprietary resin injection solution, Teretek®, to raise and re-level the floor. The project was successfully completed over four nights without disrupting Farmers’ daily retail operations.


Mainmark was required to raise and re-level a large area of the concrete slab on the ground floor of the Farmers department store in Whangarei.

The 800m² space needed to be brought back to level without interrupting Farmers’ normal trading hours of 9am until 5:30pm on most weekdays, 9am until 11pm on Farmers Club Member Thursdays, 9am until 4pm on Saturdays, and 10am until 4pm on Sundays.

Mainmark needed to ensure the store was kept clean, free of debris, and safe to continue trading throughout the project.


Mainmark recommended its state-of-the-art engineered resin injection solution, Teretek®, to stabilise the soil underneath the slab, and raise and re-level the floor. The Mainmark team used a self-contained operations rig with two injection guns simultaneously to speed-up the process and ensure an even lift.

Teretek® was specified because of its unique two-in- one capability that improves the foundation ground, while raising and re-levelling the structure. It provides an alternative to the more expensive and disruptive traditional concrete underpinning process. Mainmark technicians identified a number of injection points, then injected the Teretek® expanding polyurethane resin mix through small tubes into the ground. On entering the ground, the components mix together and quickly expand by chemical reaction, which strengthens the ground underneath and re-levels buildings quickly and with minimal disruption.

Mainmark worked at night, outside Farmers’ trading hours, to ensure that customers and staff were not affected by the project. Mainmark screened-off and protected the Farmers’ merchandise, which wasn’t removed from the store, and kept the store clean throughout the process. Farmers’ staff could enter the store each morning and conduct business as usual without delay or interruption.

Mainmark completed the project in just four night shifts. The product shelves were corrected as the floor slab was re-levelled and there was no interference with normal store operation.

Walter Hayman, at ARCO Group Ltd, said, “ARCO Group Ltd was the main contractor for the Farmers redevelopment in Whangarei. ARCO Group contracted Mainmark to complete the floor levelling of the front half of the building. We were very impressed with Mainmark’s work ethics and would not hesitate to recommend them to anyone else looking to complete similar works.”


Download a pdf version of this project here

Ground strengthened and building re-levelled at large shopping centre
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Ground strengthened and building re-levelled at large shopping centre

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Mainmark Ground Engineering (NZ) Ltd





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