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Contact us to discuss your problem — settled slab, cracked floor, void beneath infrastructure, or water ingress. We listen, ask the right questions, and arrange a free site visit with one of our engineers.
Polyurethane Grouting
Expanding resin for slab lifting, void filling, and ground strengthening — same-day trafficable.
POLYURETHANE GROUTING
Polyurethane grouting uses expanding two-component resin systems injected through small-diameter ports to fill voids, lift settled structures, strengthen weak ground, and seal water ingress — without excavation, without major disruption, and in most cases with same-day return to service. It is one of the most versatile and minimally disruptive ground treatment tools available, and GSI NZ operates purpose-built resin injection equipment with experienced crews who have delivered polyurethane grouting programmes across New Zealand.
The core application is slab lifting and void filling beneath concrete slabs, pavements, and infrastructure that has settled due to void formation, soil erosion, or loss of sub-base support. Resin is injected through small holes (typically 12—16mm diameter) drilled through the slab at a regular port pattern. As the resin expands, it fills the void beneath the slab and applies a controlled lifting force, re-levelling the structure with millimetre precision. The same-day cure means traffic and operational loading can resume within hours of completion, making polyurethane grouting well suited to roads, warehouse floors, airport aprons, and other infrastructure that cannot sustain extended closures.
Beyond slab lifting, polyurethane grouting is used for ground strengthening beneath foundations where soil has been weakened by moisture, piping, or biological activity. Expanding resin permeates into the weak zone, encapsulating soil particles and increasing the bearing capacity of the ground without the need for excavation or underpinning. GSI NZ has used this technique to strengthen ground beneath operational buildings, industrial floors, and infrastructure foundations across New Zealand.
Polyurethane grouting is also effective for sealing active water infiltration — stopping leaks in joints, cracks, and interfaces in concrete structures including retaining walls, culverts, tunnels, and basement slabs. Hydrophilic resin systems react with water to form a flexible, watertight seal, making them the preferred solution where conventional cementitious grouting cannot achieve a reliable seal in wet conditions.
APPLICATIONS INCLUDE
- Slab lifting and re-levelling beneath settled concrete pavements and floors
- Void filling beneath roads, warehouse floors, airport infrastructure and industrial slabs
- Ground strengthening beneath foundations on weakened or voided soil
- Waterproofing and crack sealing in retaining walls, culverts and basement structures
- Pipe annulus grouting and culvert rehabilitation
- Bridge abutment void filling
- Sub-base stabilisation beneath operational infrastructure
THE GSI DIFFERENCE
ONE TEAM.
ONE CONTRACT.
- →12—16 mm injection ports, no excavation, no spoil, for precise slab lifting with millimetre-level control and same-day return to traffic or use.
- →When the scope is larger than polyurethane: foamed concrete, in-situ mass stabilisation, or deep soil mixing from the same team, under the same contract.
- →Free site assessment before every job — findings presented, scope fixed, and underlying cause addressed. All work is backed by a maintenance-supported performance warranty: if the problem returns, we return.
HOW WE APPROACH POLYURETHANE GROUTING
Free Site Assessment
We come to you at no charge. The assessment covers slab condition, underlying ground, void extent, and the root cause of settlement. A Chartered Engineer confirms whether polyurethane grouting is the right solution for the specific site conditions.
Consultation
We present our findings, explain what's causing the problem, and outline the proposed solution. You receive a fixed-price scope before any work proceeds — no surprises.
Resin Injection
Resin is injected in controlled increments with the slab level monitored continuously — injection stops precisely when the target elevation is reached.
Project Review & Warranty
We follow up post-completion to confirm the outcome and long-term stability.
CAPABILITY
Residential, Commercial & Infrastructure
Polyurethane grouting is suited to domestic driveways, warehouse floors, carparks, industrial slabs, and infrastructure pavements alike. The same process (12—16 mm ports, expanding resin, same-day return to service) scales from a settled residential driveway to a large industrial floor or road pavement void.
Cured polyurethane is chemically inert, water-resistant, and maintains its volume and strength over time; it does not shrink or dissolve. For below-ground structural waterproofing, resin injection seals cracks and joints without excavation, providing a durable barrier to water ingress. GSI NZ deploys polyurethane grouting as part of a broader specialist grouting capability that includes foamed concrete, DSM, IMS, and jet grouting, so the right method is applied to every project.
Specialist Grouting Overview →FREQUENTLY ASKED QUESTIONS
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Polyurethane Grouting
→ Fast & Precise.
Void filling, slab lifting, or pipe annulus grouting — our polyurethane grouting teams work with minimal disruption and deliver results you can see immediately.
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