Foundation crack repair: epoxy vs polyurethane, and cost per foot
Most poured-concrete foundation cracks are sealed by injecting epoxy or polyurethane. The choice depends on whether you are restoring strength or just stopping water — and the cost is a simple per-foot calculation.
Cracks in a poured-concrete foundation are common and, in many cases, minor — concrete shrinks as it cures and moves a little with the seasons. The everyday repair is injection: filling the crack from the inside face under pressure so the fill penetrates the full depth of the wall. Two resins dominate, and they do different jobs. Getting the choice right matters more than the price, and the price itself is easy: linear feet of crack × your contractor's $/ft, plus any setup fee, which is what the crack repair cost tool computes.
Epoxy vs polyurethane — the real difference
- Epoxy cures rigid and strong. It bonds the two faces of the crack back together and can restore some of the wall's original strength, so it is the choice for structural, non-moving cracks in poured concrete. It cures relatively slowly, which lets it flow deep into a tight crack.
- Polyurethane stays flexible and foams to fill voids. It is a waterproofing repair: it seals against leaks and tolerates minor ongoing movement without cracking, but it does not add structural strength. It is the choice when the goal is a dry basement rather than restored strength, and for cracks that are actively weeping.
Rule of thumb: epoxy for strength, polyurethane for water. If a crack is both structural and leaking, the engineer decides — and if the crack is moving, injection alone may not be the answer at all.
Cost per foot, worked
Injection is priced by the length of the crack. Suppose you have an 8 ft vertical crack and your contractor charges $60 per foot with a $150 setup fee for the visit and materials. The estimate is 8 × $60 + $150 = $630. Enter your own numbers in the crack repair calculator; because you supply the $/ft, the estimate never goes stale with material prices. A short single crack is one of the cheapest foundation repairs there is, which is why it is worth doing early — before water finds it.
When a crack is a warning, not a chore
Injection is right for stable, vertical or diagonal shrinkage cracks. Stop and get a licensed structural or geotechnical engineer if you see any of these instead: a horizontal crack (often a sign of pressure pushing the wall in), a crack wider than about a quarter inch, a stair-step crack in block, one side of a crack sitting proud of the other (shear), or a crack that keeps growing. Those signal movement or hydrostatic pressure, and the fix may be carbon-fiber straps (see the bowing-wall guide) or piering, not a tube of resin.
Fix the water, not just the crack
Many foundation cracks leak because water is collecting against the wall. Sealing the crack without correcting drainage often just moves the leak a foot over. Pair crack repair with the drainage that caused it — gutters, downspout extensions, regrading, or a French drain — and with interior measures like interior drain tile where water is entering at the floor. The waterproofing methods table lays out which approach suits which water source.
How injection actually works
Injection is a low-pressure process done from the inside. The crew mounts a line of ports along the crack, seals the surface between them, and pumps resin through each port so it travels the full depth of the wall rather than just skinning the surface. That through-wall fill is why injection outperforms a smear of hydraulic cement on the face: it addresses the crack all the way to the exterior, where the water actually enters. Epoxy is pumped slowly because it cures slowly and needs time to penetrate; polyurethane is pumped and then reacts with moisture in the crack to foam and expand, which is exactly why it tolerates a damp, actively leaking crack that epoxy would struggle to bond in.
Preparation matters more than the resin brand. A crack that is not properly ported and surface-sealed will let resin blow out the face instead of filling the void, so a clean, methodical install beats a premium material applied carelessly. This is also why a very fine hairline may be left alone: if it is stable, dry and purely cosmetic, monitoring it can be the right call, and you spend the injection budget where water is actually getting in. When in doubt about whether a crack is cosmetic or structural, that is the moment to bring in an engineer rather than a caulk gun.
Estimate, not a diagnosis
The per-foot number is a planning estimate from your own price, not a verdict on whether injection is the correct repair. Structural cracks and any sign of movement are an engineer's call, and some crack work touches structural scope that needs a permit. Use the calculator to budget and to compare quotes; use a professional to decide the method.