Repair methods
Polyurethane crack injection
My basement crack leaks and it moves a bit. What can be injected into that?
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.
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.
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.
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.
Usually worth planning a repair
Conditions in this band do not usually become emergencies, but they rarely improve on their own and repair costs tend to rise with the affected area.
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.
Common questions
Does polyurethane injection fix the crack?
It stops water travelling through it, which for many homeowners is the actual problem. It does not bond the crack structurally and does not claim to. If the crack raises a structural question — horizontal direction, a bowed wall, measurable ongoing movement — that question needs answering separately.
Can it be done while the crack is leaking?
This is one of its practical advantages: many polyurethane formulations react with water and expand, so damp or actively leaking cracks are workable candidates rather than obstacles. That is a meaningful difference from epoxy, which bonds poorly in wet conditions.
Should I fix the outside instead?
Look at it first, because it is frequently cheaper and addresses the source rather than the path. Downspouts discharging beside the wall and ground sloping towards the house are common and fixable. Injection is a good tool; it is a better tool once less water is arriving.
Where to go next
Worth comparing
What drives the cost
Methods that may apply
Want a straight answer about polyurethane injection?
Both decision tools are free and need no contact details. If you would rather have somebody local look at it, you can ask us to review whether we can match you — and we will say plainly if we cannot.