A terrace home built in the 1900s had a single-level extension added in the 1990s. That single-level extension had experienced differential settlement of up to 35mm, creating internal and external wall cracking, misalignment of doors and windows, cracked floor and wall tiles in the bathroom, and an unlevel internal floor. It was essential to rectify this subsidence to prevent further damage to the home.
A number of approaches were tried, including polyurethane resin and conventional jacking but, due to various factors including ground conditions and the type of soil involved, these approaches were unsuccessful.
Mainmark was contracted to re-level and re-support the extension. Mainmark recommended JOG Computer Controlled Grouting because it was non-invasive, offered the ability to use multiple lifting points with finite control, and lifted the entire structure evenly and consistently.
Mainmark positioned seven injectors directly beneath the property’s footings and injected in sequence, achieving a 32mm lift in the worst-affected area. This returned the internal floor levels to within acceptable tolerances of plus or minus 5mm. The entire project was completed within two days with minimal disruption to the adjoining tile and sandstone finishes and the cost was approximately half that of other, more traditional approaches.
Mainmark needed to provide a cost-effective solution that would re-support and re-level the single-story extension to the home. The project needed to be non-invasive and not require excavation or significant disruption to the homeowner.
The single-level, double-brick structure was founded on a continuous concrete strip footing on an approximately two-metre fill layer.
This was Mainmark’s first small-scale, residential project in Australia using JOG Computer Controlled Grouting. The solution provided a faster and non- disruptive alternative to conventional methods, which would have required two weeks, doubled the cost of remediation and involved excavation and major disturbance to surrounding paving and gardens.
JOG Computer Controlled Grouting corrects un- level ground without the use of hydraulic jacks and temporary lifting platforms. There is no mess
or vibration, and neighbouring properties are not affected. Because the approach uses advanced grout monitors, it can achieve a very high degree of accuracy while placing minimal stress on separate sections of the structure. All parts are supported and brought up together using small, sequenced injections of high-mobility cementitious grout.
Using JOG, Mainmark was able to bring the extension building back to within 5mm of level, quickly and
easily. The ground underneath the building is now stabilised, reducing the risk of further subsidence and subsequent damage. The works were completed successfully in just two days.
John Barker, the property’s owner, said, “Mainmark was excellent to deal with, persevering with different options and approaches until we arrived at the right solution, and achieved a great result. Mainmark used its JOG grout injection system which, over two days, succeeded in raising parts of the subsiding rear extension of my house. They mobilised on-site, did the work, and then left the site in a clean and tidy condition. I would definitely recommend Mainmark to others who were looking for a system to lift subsiding structures with minimal invasion.”
Project Resources & Downloads
Re-levelling and re-supporting a home using JOG
JOG Computer Controlled Grouting
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JOG and Teretek® Used to Re-level a Two-storey House
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