Polyurethane crack injection

This is the situation polyurethane injection exists for. A flexible resin is injected into the crack, where it reacts and expands to fill the void and form a seal that can accommodate some continued movement. Stopping the water does not settle whether the wall itself is a question, which is why reading the crack's direction first matters.

It is a water-exclusion repair and it does not claim otherwise. That honesty is useful: it means the decision is about whether stopping water is what you need, not about which product is stronger. If what you need is continuity across the crack rather than a seal, the comparison with epoxy injection is where that choice gets made.

What the method is

Ports are set along the crack and flexible polyurethane resin is injected. Many formulations react with water and expand, which is why they suit damp and actively leaking cracks that would defeat a rigid resin. Whether that is the right response depends first on what the leak is telling you, which is the subject of water entering through concrete cracks.

The cured material remains flexible, so seasonal opening and closing of the crack does not necessarily break the seal.

The result is water exclusion through the thickness of the element rather than a surface patch.

What it does not do

• It makes no structural contribution. The crack faces are sealed, not bonded to carry load.
• It does not address the cause. Water arriving because of exterior drainage will keep arriving.
• It does not stop movement, and large movement can still exceed what the seal accommodates.
• It does not improve appearance meaningfully, and injection ports leave visible marks.

What you can safely check yourself

• Establish the timing of leakage relative to rain before committing, since that indicates where the water is arriving from.
• Note whether the crack moves seasonally, which is the case this method is designed for.
• Check what the exterior is doing with roof and surface water first, because that is often the cheaper intervention.

When professional evaluation matters more

• The crack is horizontal, or the wall is bowed — structural assessment comes first
• Water appears with no correlation to rainfall, which suggests a plumbing source worth finding
• Leakage is substantial or appears in several places, suggesting a broader drainage question

Questions to ask whoever comes out

• Why polyurethane rather than epoxy here?
• Are you making any structural claim for this repair? If not, is anything needed structurally?
• What outside would you change so less water arrives at this crack?
• What will the ports look like when finished?
• What does the warranty cover — this crack, this wall, or water entry generally?

Where estimates for this commonly differ in scope

These are the places two prices for apparently the same work stop being comparable.

• Injection is often sold alongside interior drainage systems; establish which part of the price is which.
• Exterior drainage correction is usually the cause-side intervention and usually a different trade.
• Warranty scope varies widely between "this crack will not leak" and much narrower promises.

Who tends to do this work

• A waterproofing contractor
• A concrete repair specialist

ConcreteOwner does not inspect, certify or approve contractors. This describes which trade usually holds this work, not a recommendation of anybody in particular.