Sunken Garage Slab, Cracked Brickwork & Uneven Concrete Problems

For years, the homeowner of this Loganholme property watched helplessly as the front of his house slowly sank. The garage slab releveling became a growing concern as cracks appeared in the brickwork, the concrete garage floor developed uneven slabs, and the garage door shifted out of alignment. The driveway also showed signs of sunken slabs and concrete sinking—common problems that pointed to deeper structural issues beneath the surface.

As a capable DIY enthusiast, the homeowner initially considered tackling the problem himself—replacing the driveway slab and using second-hand jacks to repair the garage. However, after researching effective alternatives to concrete replacement and mud jacking, he decided to entrust the repairs to Buildfix, confident in our expertise and proven GeoPoly® resin technology.

Foundation Instability from Poor Soil and a Sinking Garage Floor

The house, built in 2002 on a waffle slab—a common building technique in Australia—faced long-term issues due to poor ground preparation and the absence of a proper structural assessment during construction. While waffle slabs can be an efficient option, their success relies on a stable, compacted base. In this case, the soil beneath failed to support the concrete floor evenly, leading to sunken concrete and cracks across various sections of the garage.

The uneven slope between the garage and the road created a noticeable drop, and the entire slab had shifted out of its level position. This made the surface unsafe and compromised the structural integrity of the space, especially around the affected area where high edges had formed. The situation called for more than concrete patch techniques or DIY methods—traditional options like fresh concrete or additional concrete wouldn’t solve the underlying problem.

To restore the flat surface and prevent further movement, our team needed to stabilise the ground and raise and relevel the garage floor using advanced concrete leveling techniques. With limited access due to the parked motorcycles, and even a drying tea towel to work around, this project required careful planning, the right compounds, and a non-invasive solution.

Concrete Slab Jacking with Foam Injection to Relevel and Stabilise

Upon inspection, our team identified strategic points for drilling under the garage slab while accounting for uncertainty about the presence of footings. As experienced ground surgeons, we knew that any step taken had to minimise disruption while delivering lasting structural results.

Using our proprietary GeoPoly™ resin, we injected the material deep into the ground through carefully placed lances. This method offered one of the most efficient ways to address subsidence repairs without the need for additional cement or invasive demolition. The expanding resin filled voids and stabilised the soil beneath the concrete surface, acting as a high-performance concrete compound to strengthen the base.

Once the ground was stable, the controlled expansion of the resin carefully lifted the slab. This precise concrete repair technique avoided the need for traditional tools like a trowel or concrete grinding to achieve a smooth finish. Instead, with millimetre-level precision and laser monitoring, we relevelled the floor without damaging the existing structure or affecting the homeowner’s prized motorcycles.

The results were extraordinary. The garage wall was lifted by over 45mm, reversing its subsidence and closing most of the gaps in the brickwork. The entire process took less than four hours to complete, causing minimal disruption to the homeowner.

The sinking garage was stabilised and relevelled with lasting results, providing the homeowner with peace of mind. The Harley Davidson bikes remained safe and sound throughout the repair, and even the tea towel stayed in place—untouched.

Seeing similar signs of sunken concrete in your garage or driveway? A free assessment checks the slab and explains what concrete relevelling can do — without moving a thing.