Specialist negative-side injection waterproofing for lift pits and below-ground carparks in NSW u2014 stopping active concrete leaks from inside, without disturbing structure above.
Lift pits and underground carparks in NSW sit at or near the water table in the majority of high-density urban locations across Sydney, Newcastle, Wollongong and the Central Coast. They are constructed from reinforced concrete u2014 primarily walls, floor slabs, and pile caps u2014 that was designed for structural load rather than for sustained watertightness. Over time, the concrete is subject to shrinkage cracking, thermal movement cracking, construction joint failure, and the slow deterioration of any waterproofing membrane applied during original construction.
nThe result is predictable: by the time a building is 10u201320 years old, a significant proportion of Sydney’s lift pits and basement carparks have some degree of active water ingress. In a lift pit, active ingress is a serious maintenance and safety issue u2014 water in the pit can cause electrical failures in the lift mechanism, create slip hazards for service personnel, and cause corrosion of the lift guide rails and sill plates. In a carpark, active ingress accelerates the chloride-induced corrosion of the slab reinforcing u2014 the most expensive and difficult-to-remediate form of concrete deterioration.
nThe challenge is access. Lift pits are confined spaces u2014 entry requires a trained confined-space entrant with appropriate equipment, atmospheric monitoring, and standby personnel. Basement carparks are occupied u2014 repair work must be staged to allow at least partial continued operation, and trade access must be managed around the vehicle movements. In both cases, excavation is not a realistic option: excavating to access the external face of an in-service building’s below-grade structure is typically impractical, enormously expensive, and impossible for lift pits in occupied buildings without decommissioning the lift entirely.
nThe solution in both cases is negative-side injection waterproofing u2014 treating the water ingress from inside the structure, without excavation, using PU injection systems that stop active water flow through cracks and joints in the concrete.
Negative-side injection is the technique of injecting waterproofing resin into a concrete crack or joint from the dry side of the structure u2014 that is, from the interior of the basement, carpark, or lift pit, injecting toward the exterior face where the water is coming from. The resin travels through the crack, reaches the water at or near the outer face, reacts, expands, and seals the crack from within the concrete.
nThis is counterintuitive u2014 the water pressure is acting against the direction of injection. The reason it works is that PU resin is a low-viscosity liquid that penetrates fine cracks under pump pressure, and its water-reactive chemistry means that as soon as it contacts the water within the crack, the expansion process begins and the foam cures in place against the water pressure. The expanding foam is stronger than the pressure trying to push water back through the crack.
nFor lift pits and carparks, Econyc’s negative-side injection process follows the same sequence as all PU injection work u2014 survey, port installation, flushing, injection, cure, documentation u2014 with the addition of the confined space and/or traffic management requirements specific to these environments. See our PU Injection service page for the full step-by-step process.
nProducts used:
nLift pits are classified as confined spaces under the NSW Work Health and Safety Regulation 2017. Confined space entry requires:
nEconyc’s lift pit injection team meets all confined space entry requirements. We carry our own atmospheric monitoring equipment, confined space entry rescue equipment, and all required safety documentation. We coordinate with the building manager and lift maintenance company to ensure the lift is decommissioned and locked out for the duration of the injection work, and we provide all required work method statements and safe work method statements (SWMS) prior to site access.
nThe lift can typically be returned to service within 4u20138 hours of injection completion u2014 the same day as the work in the majority of cases.
Injection work in occupied underground carparks requires careful coordination with the building manager and strata to minimise disruption. Econyc’s standard approach:
nFor large carparks with multiple active ingress points, injection can often be completed in stages over several nights or weekends without any closure of the facility to residents. This staged approach is more disruptive to the injection team’s productivity but is the practical requirement for occupied strata buildings.
As with all injection waterproofing work, Econyc does not provide a workmanship warranty on lift pit or carpark injection. Lift pits and underground carparks are exactly the kinds of structures where the factors that determine long-term injection performance u2014 ongoing structural movement, groundwater level variation, the dynamic loads from lift mechanisms and vehicle traffic u2014 are entirely outside the injection contractor’s control.
nWhat we provide is documented completion to the required standard: port locations and depths, products and volumes injected, and the result at each port (resin appearance at adjacent port confirming full crack penetration). This documentation is provided to the building manager and strata manager on completion and can be shared with engineering consultants reviewing the condition of the structure.
nFor structures where the injection is part of a broader structural monitoring and maintenance programme (which is best practice for any building over 15u201320 years old with active concrete deterioration), our documentation integrates with the maintenance programme records and provides a baseline against which future inspections can be compared.
How long does lift pit injection take?
nFor a standard residential lift pit with 3u20138 active ingress points, the injection work itself typically takes 3u20136 hours including confined space setup, drilling, injection, cure monitoring, and cleanup. Allowing for lift decommission and recommission, the total out-of-service time is typically 6u201310 hours u2014 usually completing within a single working day.
Can injection be done while the carpark is open?
nYes u2014 with appropriate traffic management to exclude vehicles from the immediate work zone. In practice, most carpark injection work is done outside peak hours or overnight to minimise disruption. We can discuss scheduling options with the building manager to find an approach that minimises the impact on residents.
Does the lift need to be decommissioned for lift pit injection?
nYes u2014 the lift must be locked out before confined space entry to the pit. This is a non-negotiable safety requirement. The lockout is arranged in coordination with the lift maintenance company, and the lift is returned to service as soon as injection is complete and the confined space entry has been formally closed. We aim to complete this within a single day to minimise the inconvenience to building occupants.
What if the injection doesn’t stop the leak?
nIf resin does not appear from adjacent ports during injection u2014 indicating incomplete penetration u2014 we continue injection until it does. We do not leave a site with unresolved active flow. For very high-flow situations where a standard PU product cannot overcome the flow rate, we use a two-stage approach: hydraulic cement to reduce the flow to a manageable rate, followed by PU injection for the final seal. Persistent leaks that cannot be resolved by injection alone may require a drainage system (a collection channel and sump pump) as a secondary measure.
How soon after injection can the lift be returned to service?
nTamPur 116 achieves full cure within 24 hours, but initial foam formation and seal occurs within 15u201330 minutes of injection. In most cases, the lift can be returned to service within a few hours of injection completion u2014 we advise on the specific timing based on the extent of injection and the ambient temperature during cure.
Contact Econyc today for a free site inspection and fixed-price quote. Licensed, insured, and experienced in specialist injection waterproofing across NSW.