A two-storey residential property in Hoppers Crossing, Victoria, was suffering from severe differential settlement of up to 95mm. The brick veneer house, with a 145m2 footprint, was approximately nine years old and built on a conventional raft slab footing. The edge beam of the raft slab was unusually deep, measuring 2.4m below ground.
Settlement had occurred at three separate corners of the property, with the raft slab causing the home to tilt towards the most affected corner. Cracks had started to appear on the walls and in the large ceramic floor tiles, the doors and window frames had warped, the garage door was no longer flush to the ground, and some expansion joints had begun opening.
As the property was under warranty, the owner sought resolution from the original builder. The warranty builder engaged Expertise Building Services to provide a solution which would avoid the need to knock down the house. Due to the home’s deep footings, there were very few options available to re-level the property. Underpinning would have been extremely expensive, requiring intrusive excavation works, and would not have been able to adequately support the internal sections of the slab.
Mainmark were contracted to deliver a unique solution by using two of its proprietary non-invasive re-supporting and re-levelling solutions together to remediate the property. A relatively small on-site operational footprint was achieved by placing the required equipment at the front of the property.
On behalf of the original builder, Expertise Building Services sought a cost-effective and logistically viable solution that would raise, re-level and re-support the property, bringing the differential settlement back to a level of +/- 10mm of the home’s target relative level (RL).
The client’s consulting engineer specified Mainmark’s Teretek resin injection which was required to provide a cost-effective solution that would avoid the need to demolish the house.
Due to the significant depth of the footings and the site’s reactive clay soil, Mainmark recommended using a combination of JOG Computer-Controlled Grouting and Teretek resin injection to remediate the home. JOG was used as the primary technology to re-level the slab, with Teretek used as a supplementary solution to provide additional slab support and void fill.
JOG is a computer-controlled multi-point cementitious levelling process. It precisely monitors re-levelling to the millimetre, with the cementitious grout mix delivered sequentially via narrow injection ports to targeted depths beneath a building’s footings. Unlike traditional underpinning methods, the process is relatively non-invasive and requires no digging or excavation, causing no damage to the structure being treated. To improve the differential settlement, Mainmark needed to locate the edge beam of the central raft slab and drill through the footings to depths of up to 2.4m below ground. Achieving adequate lift at such depth was challenging due to side wall friction, therefore a controlled, multi-point approach using JOG was required to avoid placing undue stress on the central area of the slab.
Teretek resin injection was then applied as a secondary solution to provide added support to the foundation and fill any resulting internal voids. Teretek is a two-in-one ground engineering solution that can both improve ground-bearing capacity and re-level structures. It can quickly and effectively fill voids, and is applied via a process similar to keyhole surgery.
Mainmark successfully re-levelled the entire length of the three affected side walls, lifting the slab to within +/- 10mm of its target RL without the need for soil removal. Mainmark is uniquely placed to be able to deliver projects of this size and scope utilising two complimentary, proprietary non-invasive solutions. The project took Mainmark a total of only 14 days to complete and was delivered within budget to the client’s complete satisfaction.
Paul Richey, Expertise Building Services, said, “My dealings with Mainmark were nothing but professional. They ensured all aspects of the work, including any queries I had, were thoroughly explained so all parties were aware of the process and that the outcome would be achievable prior to the project commencing. This gave the owner the reassurance and confidence that the home could be stabilised and that there would be no surprise costs or variations to the work.”
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JOG Computer Controlled Grouting And Teretek® Resin Injection Combined To Save House From Demolition
JOG Computer Controlled Grouting
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Ground Beneath Heritage Office Strengthened with Uretek®
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