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The Canterbury and Kaikoura earthquakes represent one of the most traumatic times in New Zealand's history. Many people whose homes were damaged by the earthquakes continue to experience negative impacts on their quality of life due to unresolved issues with their homes, including houses which are subsiding or sitting on unstable land.

Even now, nearly 10 years after the magnitude 6.3 earthquake, many Canterbury residents are working towards resettling their nerves and rebuilding their lives and homes.

One of the most important things for a homeowner to know— no matter where in New Zealand that you live— is when cracks or house movement should be investigated and how to take action.

Mainmark has successfully treated more than 30,000 sites in Australasia, from small domestic applications to large commercial, industrial, civil and mining projects.

​Mainmark Ground Engineering was well established in the Canterbury region prior to the earthquakes. It is recognised as market leader in ground engineering and asset preservation, having completed the most house re-levels in the region since the earthquakes. They also have extensive experience raising and re-levelling buildings across the whole of New Zealand with offices in Wellington and Auckland too.

"Some of the most common signs of building settlement caused by subsidence or ground movement, which our customers experience, is cracking in their walls, whether that be in the gib internally or externally, in the brickwork or cladding," says Mike Baker, an area manager for Mainmark New Zealand.

"Any settlement of the building is ultimately bending or twisting the structure out of its original alignment and causing cracking in the visible surfaces," he says. "Another symptom is that windows and doors are sticky, jamming or just simply don't operate as they should. I have seen doors that swing open or closed themselves and sometimes will no longer close fully because they have twisted."

Sinking floors, cracked walls and jamming windows can all be indicators of structural damage caused by subsidence.

Baker says he is aware there are still a significant number of houses requiring repair, post-earthquake, in addition to houses suffering from subsidence caused by other factors such as extremes in weather, leaking water pipes and poorly compacted fill material. He urges homeowners who have noticed any symptoms to contact Mainmark so an assessment can be carried out on the building and repairs can be undertaken to mitigate any further damage caused by instability of the ground or foundations.

"In Canterbury, one frustration I often see is where the homeowner has been paid out or 'settled' by their insurer or EQC without knowing what steps to take next," says Baker. "They know their house needs repairs but don't know who to contact. If a customer contacts Mainmark we can quickly assess what works need to be done to get the house back to level and, if other repairs are needed, we can put them in touch with a builder too."

Mainmark is an internationally recognised specialist in ground strengthening and earthquake remediation technologies.

Baker says Mainmark offers the world's most advanced earthquake remediation, liquefaction mitigation and ground-strengthening technologies to level-correct the building and improve the ground immediately underneath, using processes likened to keyhole surgery. Mainmark also helps fix settlement, subsidence or ground movement caused by other factors such as extremes in weather and leaking water pipes, which are very common across New Zealand. 

Mainmark offers two proprietary non-invasive solutions: Teretek resin injection and JOG Computer-Controlled Grouting. Teretek is a unique two-in-one solution that delivers both ground improvement and re-levelling and comes backed up by a 50 year product warranty. JOG is an award-winning grouting technology for re-levelling and strengthening ground beneath large structures using computer-controlled cement grout injection.

"The biggest drill hole we need to complete a job is 40mm in diameter and often as little as 6mm in some circumstances from inside a home," he says. "Once the level correction is complete, the area is ready for use immediately."