Epoxy Injection vs Polyurethane Injection — At a Glance
| Factor | Epoxy Injection | Polyurethane Injection |
|---|---|---|
| Primary purpose | Structural — restores wall strength | Water-stop — blocks leakage |
| Flexibility | Rigid — bonds permanently | Flexible — moves with wall |
| Use when crack is | Inactive (not moving) | Active or wet |
| Cure time | 24-48 hours | Minutes (expands on contact with water) |
| Best for | Hairline-to-1/4 inch dry structural cracks | Any active or leaking crack |
| Cost per crack | $400-$900 | $300-$700 |
Bottom Line
Use epoxy when the crack is structural, dry, and not actively moving — typically older settled cracks. Use polyurethane when the crack is wet, leaking, or in a wall that may move again. For active settlement, neither injection alone is enough — the underlying movement needs to be stopped first with piers.
When Injection Is Not the Right Answer
Crack injection only works on the crack itself. If a crack exists because the foundation is settling, injecting it stops the leak but the movement continues and the wall will crack again — often right next to the injection. Always investigate the cause before injecting. We perform a free inspection before recommending injection so the underlying movement is ruled out or addressed.
Epoxy in Detail
Structural epoxy is a two-part resin injected through ports along the crack. Once cured, the bond is stronger than the surrounding concrete — the wall is effectively one piece again. Epoxy needs a dry crack and an inactive structure to bond properly.
Polyurethane in Detail
Polyurethane is hydrophobic and reacts with moisture: as it's injected, contact with water in the crack causes it to expand and seal. It remains flexible after cure, so future hairline movement doesn't crack the seal. Polyurethane is the right choice for any actively leaking crack and for cracks in walls that may continue to flex with seasonal soil moisture.
Related Reading
Frequently Asked Questions
Can I inject a crack myself?
Hardware-store kits exist, but they fail at high rates because port placement and pressure require experience. Most DIY injections leak again within a year.
Does the crack disappear visually?
The crack remains visible but is sealed. Cosmetic finish is a separate step.
How long does injection last?
When applied correctly and the underlying cause is addressed, indefinitely. We warranty our injections.
Will injection prevent new cracks?
No — only addresses the injected crack. Stopping new cracks requires addressing the underlying movement.
Do you injection-repair stair-step block cracks?
Block cracks are typically structural and rarely respond well to injection alone. We usually pier-stabilize first, then cosmetically repair the block.