Leaking basement car park, sealed with PU injection — Gold Coast–Tweed corridor.

The building

A residential strata building on the Gold Coast–Tweed corridor with a single-level basement car park. Water was entering through a cold joint between the floor slab and the retaining wall during heavy rain, pooling in car bays and threatening the lift pit adjacent to the car park entry.

The problem

The construction joint had opened over time due to minor settlement and hydrostatic pressure during wet weather. The leak was active during rain events, and the body corporate had received complaints from unit owners about water in the car park and dampness near the lift lobby. The failure was localised to the joint — the surrounding slab and wall membrane were otherwise sound.

The approach

We inspected the joint, confirmed the water entry path, and determined the failure was localised to the joint rather than a broad membrane failure. PU injection was the right first option — no excavation, no closure of the car park, and the work could be carried out from inside. Excavating the external retaining wall would have required closing the car park entry and removing landscape, at significantly higher cost and disruption.

The work

We drilled a series of injection ports along the joint at an angle to intercept it mid-depth, installed mechanical packers, and injected hydrophilic resin to stop the active leak, followed by hydrophobic resin for long-term flexibility. The car park remained in use throughout, and the work was completed in a single day. The body corporate received a documented record of packer locations, resin types and volumes for their building file.

The result

The joint was sealed and the car park remained dry through the following wet season. No callback was required. The body corporate now has a documented repair record for the joint, and a clear baseline to monitor if the joint moves further in the future.