Epoxy vs Polyurethane Crack Injection: Which Foundation Crack Repair Fits the North Shore?

Published July 25, 2026 by North Shore Foundation Pros

You found a crack in the basement wall, you got a quote, and the contractor said the word injection. Then a second contractor used a different word: one said epoxy, the other said polyurethane. They are not the same repair, and picking the wrong one is how a sealed crack starts leaking again the following spring.

Here is what each material actually does, when to reach for one over the other, what the work costs on the North Shore in 2026, and the cases where no injection of either kind is the right answer. The patterns come from foundation work across Glenview, Wilmette, Winnetka, Evanston, Highland Park, Northbrook, Lake Forest, and Deerfield, where wet glacial clay makes crack behavior its own local puzzle.

The Two Methods, Side by Side

Both repairs inject a liquid resin into a crack in a poured concrete wall, under low pressure, through a series of ports set along the crack. The resin travels the full depth of the wall and cures. That is where the similarity ends. Epoxy cures into a hard, rigid solid that is stronger than the concrete around it. Polyurethane cures into a flexible foam or gel that expands on contact with water and stays elastic.

When Epoxy Is the Right Call

Epoxy is the structural option. When a poured wall has a crack that is dry, stable, and not actively leaking, epoxy injected into it bonds the two faces back together so the wall behaves as one piece again. Because cured epoxy is stronger than the surrounding concrete, a properly injected crack will typically not fail along that same line again. That is the appeal for cracks that matter structurally but are not moving.

The catch is what epoxy needs to work: a clean, dry crack and a crack that will hold still. Epoxy bonds best when there is no water in the way, and once it hardens it does not flex. If the crack keeps opening and closing, a rigid repair can simply crack again right next to the cured epoxy. So epoxy shines on a dormant crack in a sound poured wall, and it struggles anywhere water or movement is still in play. The American Concrete Institute recognizes epoxy injection as a structural crack-repair method in its repair guidance, and the American Concrete Institute is the standards body whose bulletins most reputable contractors follow.

When Polyurethane Wins

Polyurethane is the water option. It is built for the crack that is leaking right now. The resin reacts with moisture and expands to fill the crack and any irregular voids, chasing the water path and sealing it, and it will cure in a damp or actively wet crack where epoxy would not bond. Just as important on the North Shore, cured polyurethane stays flexible. When the wall flexes a hair with the seasons, the seal stretches instead of breaking.

What polyurethane does not do is add structural strength. It is a waterproofing repair, not a welding repair. For the most common North Shore basement complaint, a non-structural crack that seeps after heavy rain, that is exactly what you want. If you are dealing with water in the basement after rain, a flexible polyurethane seal on the offending crack is usually the direct fix for the crack itself.

Why North Shore Soil Tilts the Choice

Material choice is not just about the crack. It is about the ground the wall sits in, and North Shore ground is demanding. The region's dense glacial clay swells when it is wet and shrinks when it dries, and it heaves when it freezes. We cover the day-to-day effects of that in our clay soil foundation damage guide. The practical result is that many cracks here are not perfectly static. They breathe a little through the year as the clay loads and unloads the wall.

That seasonal flex is why polyurethane earns its keep on the North Shore. A rigid epoxy repair assumes the crack will stay put. A flexible polyurethane seal assumes it might not, and moves with it. Before you pick a material, it helps to know what kind of crack you have, which is where our guide to horizontal versus vertical foundation cracks comes in. A thin vertical or diagonal crack that seeps is a classic injection candidate. A horizontal crack, a widening crack, or a bowing wall is a structural warning that injection alone will not solve.

What Crack Injection Costs on the North Shore in 2026

Injecting a single non-structural crack generally runs about 250 to 800 dollars in 2026, and some contractors price a single crack at 800 to 1,300 dollars depending on its length, how easy it is to reach, and which material the job calls for. Epoxy tends to sit at the lower end, polyurethane a little higher. The per-crack number drops when several cracks are sealed in one visit, because the contractor's setup and travel are spread across the whole job rather than a single line.

Injection is one of the more affordable foundation repairs, which is part of why it is so often the right first step for a simple leaking crack. For how it compares with the bigger structural fixes, our foundation repair cost guide lays out the full range across the North Shore.

When Injection Is Not Enough

Neither epoxy nor polyurethane is a cure-all, and a good inspection is honest about the limits. Injection is the wrong tool, or only half the job, in several common situations:

• Structural cracks and bowing walls. A horizontal crack or a wall that is leaning in is a load problem. That calls for carbon fiber straps, wall anchors, or bracing, not a bead of resin.
• Concrete block walls. Injection is a poured-wall repair. Hollow block cracks along its joints and does not seal reliably with resin, so block leaks are handled with drainage or exterior waterproofing.
• Cracks driven by settlement or heave. If the wall is moving because the soil under it is settling or lifting, sealing the crack does nothing about the cause. The footing or the water has to be addressed first.
• A whole-wall water problem. When water is coming through many spots or up through the floor, the fix is a drainage system, not crack-by-crack sealing.

For that last case, our basement waterproofing page walks through interior drain tile, sump systems, and exterior solutions, and our foundation crack repair page covers how we decide between injection and structural reinforcement crack by crack. The right answer starts with a look at the wall, not a guess from the driveway.

Frequently Asked Questions

Should I use epoxy or polyurethane to fix a foundation crack?

It depends on what the crack is doing. Use epoxy when the crack is dry and structural, because epoxy is rigid and bonds the concrete back together to restore strength. Use polyurethane when the crack is actively leaking or still moves with the seasons, because it stays flexible and expands against water to seal the path. A dry hairline in a poured wall favors epoxy, a wet crack that opens every winter favors polyurethane.

How much does foundation crack injection cost on the North Shore in 2026?

Most single non-structural crack injections run about 250 to 800 dollars per crack on the North Shore in 2026, with some contractors charging 800 to 1,300 dollars depending on length, access, and material. Epoxy is usually the cheaper of the two, polyurethane runs slightly higher. Per-crack pricing drops when several cracks are injected in one visit, because setup is spread across the job.

Will crack injection stop a basement leak permanently?

Injection seals the crack itself and, done right on a poured wall, it holds for years. What it does not do is fix the water pressure outside the wall. If grading, downspouts, and drainage keep pushing water at the foundation, a new crack can open somewhere else. On the North Shore, lasting results pair injection with drainage control so the wall is not fighting saturated clay every storm.

Can you inject a crack in a concrete block foundation wall?

Not the same way. Epoxy and polyurethane crack injection is designed for solid poured concrete walls, where the resin fills a single crack from front to back. Concrete block is hollow and cracks follow the mortar joints, so injection does not seal it reliably. Block foundations that leak or crack are usually handled with interior drainage, exterior waterproofing, or reinforcement instead.

Is epoxy or polyurethane better for a crack that keeps moving?

Polyurethane. Because North Shore clay swells, shrinks, and heaves with the seasons, many cracks here flex a little all year. Rigid epoxy can re-crack next to a repair that keeps moving, while flexible polyurethane stretches with the joint and stays sealed. If a crack visibly opens and closes with the temperature, polyurethane is the safer seal, and the underlying movement should be assessed too.

Can I inject a foundation crack myself?

Homeowner injection kits exist and can work on a simple, dry, non-structural hairline in a poured wall. The risk is misreading the crack. A structural crack, a leaking crack under pressure, or a crack that is really a sign of settlement or heave needs a diagnosis first, not just resin. A quick professional inspection tells you whether injection is even the right fix before you spend on it.