Addressing subfloor and floor levelling issues in a timber home

This 1970s timber investment property in Southport, Gold Coast, had developed concerning signs of subsidence. The new owner, acting on a building inspection report, contacted their property agent for guidance. The report highlighted sloping concrete floors, cracked ceramic tiles, and hairline wall cracks. Beneath the home, gaps were visible between the timber beams and noticeably sunken concrete slabs, particularly at the rear corner.

Worried about tenant safety and structural integrity, the property agent reached out to Buildfix for a cost-effective, non-disruptive alternative to traditional restumping. The goal was to restore a level surface and prepare the subfloor for future floor coverings such as carpet or vinyl, all within a tight timeframe. The client needed a solution that didn’t require the removal of floor finishes or the use of traditional levelling compound or cement-based methods, which can be messy and slow to cure.

The most severe subsidence occurred at the rear corner, where poor drainage had caused significant soil erosion over time. Water pooling beneath the property had weakened the stumps, and while the downpipes had recently been reconnected, the damage to the concrete subfloor remained. The bedroom and kitchen floors were noticeably sloping, with soft spots and low areas making the surface feel unstable.

Traditional concrete levelling or plywood overlays would have required extensive subfloor preparation, including primer and waterproofing layers, adding time and material costs. These methods also involve multiple bags of rapid hardening compounds and curing times that weren’t viable given the owner’s tight turnaround. The challenge was to stabilise the compromised stumps, create a smooth surface, and relevel the structure—without removing existing floor coverings or disrupting underfloor heating systems that may have been installed later.

Precision floor levelling with resin injection under timber and concrete supports

With easy access to the subfloor,Buildfix applied our advanced GeoPoly™ PSR30 resin injection technique. This innovative method allowed us to target specific problem areas with precision and minimal disruption—no need for multipurpose primer, extensive packaging of materials, or lengthy setup like traditional methods.

First, we set up advanced monitoring equipment to track every millimetre of lift. We then drilled to a depth of 1800mm around each affected stump and inserted 2400mm aluminium pipes to deliver the GeoPoly™ PJ30 resin directly beneath the stumps. The resin’s high compressive strength allowed it to fill voids, stabilise the eroded soils, and gently lift the structure back into position with lasting results.

The entire rear corner was raised by 11mm, and three additional stumps were lifted by 5mm to 22mm, bringing the bedroom and kitchen floors back to level. The gaps beneath the timber beams were completely closed, and the bounce was eliminated.

Relevelled timber floors and restored subfloor integrity without restumping

Our GeoPoly PJ30 resin relevelled the home’s stumps, closed the gaps beneath the beams, and restored stability across the entire structure. This fast, non-invasive repair brought the floors back to level, eliminated the bounce, and allowed the owner to proceed with getting their new tenant in quicker and confidently.

Seeing similar signs of sinking floor stumps? A free assessment checks every stump and explains what floor pier repairs can do — without restumping.