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Crack Injection

# Crack injection that stops water at the source.

Cracks in concrete walls, slabs and structures are direct pathways for water. We inject polyurethane and epoxy resins under pressure to seal active leaks permanently — in basements, car parks, lift pits, tanks and retaining walls across SEQ.

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Remedial & repair

## A hairline crack is a highway for water

Concrete cracks for many reasons — shrinkage, thermal movement, settlement, structural loading. Most cracks are harmless. But a crack that penetrates the full thickness of a below-ground or water-retaining structure becomes a direct conduit for water, and no amount of surface coating will stop it. The water is under pressure, and it will find the path.

Crack injection solves this from within the crack itself. A resin is injected under pressure through a series of ports, filling the crack through its full depth and sealing it against water. For active leaks, hydrophilic and hydrophobic polyurethane resins react with water and expand to form a flexible, watertight seal. For structural bonding, epoxy resins restore monolithic strength.

It is a specialist technique. The choice of resin, the injection pressure, the port spacing and the surface preparation all determine whether the seal holds. Done correctly, crack injection is one of the most durable and least disruptive remedial methods available — no excavation, no demolition, sealed from the inside.

Where we inject

## Sealing leaks in structural concrete

### Basements & lift pits

Sealing leaking cracks in basement walls, lift pits and undercroft structures where water is entering under hydrostatic pressure.

### Car park structures

Injection of cracked slabs, walls and construction joints in below-ground and elevated car parks to eliminate ingress and protect reinforcement.

### Tanks & retaining walls

Watertight sealing of cracks in water tanks, bunds, retaining walls and other water-retaining or water-excluding structures.

### Construction & cold joints

Treatment of leaking construction joints and cold joints, a common and often-overlooked ingress path in poured structures.

### Structural crack bonding

Epoxy injection to structurally re-bond cracked concrete and restore load transfer, where specified by an engineer.

### Active, running leaks

Fast-reacting polyurethane systems that seal even actively running leaks, curing in the presence of water.

The injection process

## How pressure injection seals a crack

#### Assess the crack

We determine the crack’s nature — active or dormant, structural or non-structural, wet or dry — which dictates the resin type and method.

#### Install injection ports

Ports are drilled and set at calculated spacing along the crack, angled to intersect it through the section, and the surface between them sealed.

#### Inject under pressure

Resin is pumped under controlled pressure from the lowest port upward, filling the crack through its full depth until it refuses.

#### Cure & finish

Once cured, ports are removed and the surface made good. For active leaks, the reaction forms a flexible seal that accommodates future movement.

Choosing the right resin

## Matching the resin to the crack

The single most important decision in crack injection is resin selection. We match the system to the specific conditions of your crack.

- Hydrophobic polyurethane — for active water leaks; reacts with water to form a firm, closed-cell watertight seal.
- Hydrophilic polyurethane — flexible seals in moving or damp cracks, accommodating ongoing structural movement.
- Epoxy resin — high-strength structural bonding of dormant cracks to restore monolithic concrete, where an engineer requires it.
- Correct pressure & port spacing — calculated to the section thickness and crack width to achieve full-depth fill.

Common questions

## Crack Injection FAQs

Yes. Active leaks are exactly what hydrophobic and hydrophilic polyurethane resins are designed for — they react with the water present in the crack and cure to form a watertight seal, even while water is flowing. In many cases we can stop a running leak in a single visit.

For the crack that is injected, yes — a correctly injected crack is sealed through its full depth and stays sealed. Where a structure is subject to ongoing movement, flexible polyurethane systems accommodate that movement. If new cracks form elsewhere due to a broader structural issue, those would be separate — which is why we assess the cause, not just the symptom.

No — that is a key advantage. Injection is carried out from the accessible (usually internal, negative) side of the structure. There is no need to excavate around the outside of a basement or retaining wall, which makes it far less disruptive and costly than external tanking.

Epoxy injection can structurally re-bond a cracked section and restore load transfer, but whether a crack is structural — and how it should be treated — is an engineering question. Where structural cracking is involved, we work to an engineer’s specification.

Related services

## Explore related work

Concrete Leak Sealing
Joint Repair
Basement Waterproofing
Remedial Waterproofing
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## Seal that leaking crack

Water entering through a concrete crack only gets worse — and corrodes the steel inside. Book an assessment and we’ll seal it at the source.

Request an assessment
Call 0488 773 232