Crack injection Vancouver contractors get called for regularly — and it is one of the most commonly misspecified repairs in commercial concrete work. The material chosen for crack injection is not an interchangeable preference. Epoxy and polyurethane behave fundamentally differently, and using the wrong one does not produce a neutral result. It produces a failure. Understanding the two systems, and the assessment process that determines which one applies, is something every property manager and strata engineer should have a working knowledge of.
The Two Systems: What They Are and What They Do
Epoxy injection uses a two-component structural epoxy resin that is mixed at the injection port and delivered into the crack under low pressure. When cured, epoxy is rigid and bonds to the concrete at tensile strengths that often exceed the concrete itself. It does not flex. It does not compress. Its purpose is to restore the structural continuity of the cracked section — to make the concrete behave as though the crack was never there.
Polyurethane injection uses a single or two-component resin that, depending on the formulation, either foams on contact with moisture (hydrophilic) or remains a gel (hydrophobic). When cured, polyurethane is flexible and compressible. It does not bond to the crack faces with structural strength. Its purpose is to stop water from passing through the crack — it is a waterproofing application, not a structural one.
Both systems are injected through ports drilled or surface-mounted at regular intervals along the crack. Both require low-pressure equipment and careful monitoring to ensure full penetration. Beyond that, they are designed for entirely different problems.
When to Use Epoxy
Epoxy belongs in dead cracks.
A dead crack — also called a static crack — is one that has stopped moving. The cause of the cracking has resolved, the concrete has stabilized, and the crack width is not changing. You can verify this by applying small witness marks (tell-tales) across the crack at multiple points and monitoring them over four to six weeks. If the marks do not crack or separate, the crack is static. Epoxy is the right choice when the crack is in a structural member — a beam, a column, a load-bearing wall, a PT slab — and you need to restore the load-carrying capacity of the section.
It is also appropriate for cracks in foundation walls and retaining walls where the wall is acting structurally and the crack has compromised its section. Dry conditions favor epoxy. The resin needs to bond to the concrete face, and a wet or actively leaking crack will interfere with adhesion and cure. If a crack is leaking actively, it usually needs to be stopped with a polyurethane system first, then re-evaluated for epoxy once the substrate has dried.
In BC buildings, epoxy injection is commonly applied to cracks in parkade structural beams, elevator pit walls with static hairline cracks, foundation walls in dry areas, and cracked slabs on grade where load transfer has been compromised.
When to Use Polyurethane
Polyurethane belongs in active cracks and wet cracks. An active crack is one that is still moving — either because the structure is still experiencing thermal movement, settlement, or load deflection. If you inject epoxy into an active crack, the rigid epoxy will fracture under the movement, usually alongside the repair rather than through it, leaving you with a new crack adjacent to a plugged one. Polyurethane is the right choice when the crack is leaking. Hydrophilic polyurethane foams aggressively on contact with water, filling the crack volume and stopping the water path.
This is how elevator pits, underground parkade walls, and foundation walls in contact with the water table are typically treated. The foam expansion is what creates the seal.
Non-structural applications also default to polyurethane. If a crack in a retaining wall face is not carrying load but is admitting groundwater, polyurethane stops the water without needing to restore the structural section.
In areas with ongoing seasonal movement, polyurethane accommodates that movement without re-cracking.
Typical polyurethane applications in BC buildings include leaking parkade perimeter walls, elevator pit base cracks with active water ingress, foundation walls in contact with groundwater, and retaining walls where drainage behind the wall has failed.
What Happens When You Use the Wrong Product
Epoxy in a moving crack. The epoxy cures rigid, the crack continues to move, and the concrete fractures adjacent to the repair within a few thermal cycles. Now you have the original crack plugged but a new crack running parallel to it. The repair has relocated the failure, not eliminated it.
Polyurethane in a structural crack. The crack is sealed against water, but no strength is restored. If the cracked member is carrying load, it is still carrying load across a discontinuous section. The polyurethane foam has no meaningful tensile strength. From a structural standpoint, the crack is still there.
These failures come up regularly on sites where a non-specialist contractor has done the work without proper assessment. The building owner pays twice: once for the incorrect repair and once to redo it properly.
The Injection Process
Whether epoxy or polyurethane, low-pressure injection follows the same basic sequence.
Ports are installed along the crack at spacing equal to approximately the slab thickness — so a 200 mm slab gets ports at roughly 200 mm centres. On a vertical crack in a wall, injection starts at the bottom and works up; gravity helps fill the crack.
The crack faces are cleaned and sealed at the surface between ports using an epoxy paste or surface cap, leaving only the ports open. Material is then injected at low pressure — typically under 60 psi — at each port in sequence. The goal is to fill the crack completely from face to face. Injection continues at each port until material appears at the adjacent port, confirming the crack has been bridged. The injection technician monitors pressure and flow rate throughout.
A sudden pressure drop usually means the material has exited somewhere unexpected — either another crack or a void. A sustained high pressure with no flow usually means the port is blocked or the crack has been bridged prematurely on the surface.
Cure times vary by material and ambient temperature. Epoxy typically achieves full strength in 24 to 48 hours at 20 degrees Celsius. Low temperatures slow cure significantly — below 5 degrees Celsius, heated enclosures or heated materials may be required.
How Contractors Assess Which System to Use
Assessment before injection is not optional. A crack that looks like a maintenance item can be evidence of ongoing structural movement or active water infiltration that changes the whole repair approach.
Crack mapping is the starting point — every crack is documented for width, length, depth where accessible, orientation, and location relative to structural elements. Width is measured with a graduated crack comparator card, not by eye. A crack under 0.2 mm wide in a non-structural element is different from a 0.5 mm wide crack in a PT slab edge beam. Moisture assessment comes next. Is the crack dry, damp, or actively leaking?
At what time of year, and does the condition change seasonally? This determines whether epoxy is viable or whether polyurethane is required. Structural determination requires understanding what the cracked element is doing. Is it load-bearing? Is the crack through the full section or only partway?
Has there been any change in the above-grade loading recently — new mechanical equipment, storage loading, vehicle impact? This analysis is what determines whether the repair is a maintenance item or whether a structural engineer needs to be involved.
Cost Range and What Affects Price
Crack injection in BC buildings typically ranges from $800 to $3,500 per linear metre of crack, depending on crack width, depth, accessibility, and material. Narrow hairline cracks take more ports and more careful low-pressure work. Wide cracks in accessible locations move faster. Site factors that raise cost include confined spaces (elevator pits, underground walls with limited access), cracks in high-traffic areas that require traffic control or lane closures, and cracks that require overnight cure under monitoring before a surface is returned to service. The material cost difference between epoxy and polyurethane is not the primary driver of project cost.
Labor, access, and preparation dominate. Specifying the cheaper material for the wrong application will produce a failed repair that costs more than getting it right the first time. A proper scope of work for crack injection includes a pre-repair assessment report, material specification with product data sheets, injection log documenting port locations, pressures, and volumes injected, and a post-injection inspection. If you are getting a quote that does not include these elements, ask why.
For a free site assessment, call Miyagi Construction at 604-809-4869 or visit miyagiconstruction.com/.
Get a Free On-Site Assessment
Tell us about your project and we'll get back to you within 24 hours. No obligation, no pressure.