Concrete Crack Repair Methods (Pharr Guide)

There are five concrete crack repair methods that actually get used, and picking the right one comes down to a single question: is the crack moving? Static cracks get bonded rigid. Moving cracks get filled flexible. Get that backwards and you'll do the repair twice.

Most people arrive at this page after standing in a hardware store aisle looking at eleven tubes that all say "concrete crack repair" and none of which say which crack. So let's sort that out.

Step one: diagnose before you buy anything

Three measurements, five minutes, no tools you don't own.

Width. Under 1/8 inch is hairline. 1/8 to 1/2 inch is a working crack. Over 1/2 inch, or wide enough to see daylight, is structural until proven otherwise.

Offset. Run a finger across it. If one side sits higher, or the two sides have shifted sideways, that's movement, not shrinkage.

Activity. Draw a pencil line across the crack at both ends and write today's date on the concrete. Come back in three months. A crack that's grown has a live cause. Filling it now is treating a symptom.

While you're down there, look at what's above and around. A crack running diagonally from the corner of a garage door opening or a window is a stress crack, and it's telling you something the crack itself can't fix.

The five methods, and when each one is right

1. Surface sealant — hairline, non-moving, cosmetic

Self-leveling polyurethane crack sealant in a caulk tube. Blow the crack out with compressed air or a shop vac, cut the nozzle small, run a bead, tool it flush. Roughly $12 and an afternoon. This handles the large majority of driveway and patio hairlines and it is entirely a DIY job.

2. Rout and fill — the workhorse for slabs

For cracks between about 1/8 and 1/2 inch, you cut the crack open into a small square channel, roughly 1/4 inch wide by 1/4 inch deep, with a crack chaser wheel on an angle grinder. That reservoir gives the filler something to bond to on two clean faces and enough depth to flex without tearing.

Then fill with a flexible polyurethane for exterior work, or a semi-rigid polyurea for interior control joints in a garage or shop, where the point is supporting the joint edges against hard wheels rather than accommodating movement. Backer rod goes in first on deep cracks so you're not pouring product into a void.

Professionally, $150 to $800 depending on total linear feet.

3. Epoxy injection — structural, static, and you want it welded

Low-pressure epoxy injection bonds the two faces back together into a single structural element. Cured epoxy is stronger than the concrete around it, which is exactly the point: you're not filling a gap, you're restoring the section.

Ports get glued along the crack at intervals, the surface between them is sealed with a paste, and epoxy is injected from the lowest port until it appears at the next one. It's used on foundation walls, beams, columns, and structural slabs.

Critical caveat: epoxy is rigid. Inject a crack that moves seasonally and the concrete will simply crack again beside your beautiful repair. Epoxy is for cracks that are done moving.

4. Polyurethane injection — the leak stopper

Same port-and-inject process, different chemistry. Polyurethane foams and expands on contact with water, chasing the leak path through the wall and sealing it. It stays flexible.

This is the right call for a leaking basement or foundation wall crack that is not structural. You're solving a water problem, not a strength problem. Professional injection commonly runs $400 to $900 per crack. DIY kits exist in the $60 to $150 range and work fine on a simple vertical crack in poured concrete.

5. Stitching and staples — cracks that keep opening

For a crack that keeps widening and can't be allowed to, you cut slots perpendicular across the crack and epoxy in U-shaped steel staples or carbon fiber strips, then fill the crack itself. It's the concrete equivalent of stitches: you're mechanically holding the two sides together.

This is a professional repair and usually a symptom that something bigger deserves a look.

Quick reference

Crack	Method	Rough cost
Hairline, static, exterior	Polyurethane sealant from a tube	$12 DIY
1/8–1/2 in, static or moving	Rout and fill, flexible urethane	$150–$800 pro
Garage or shop control joint	Rout and fill, semi-rigid polyurea	$2–$6 / linear ft
Structural, static, foundation	Epoxy injection	$400–$900 per crack
Leaking, non-structural wall	Polyurethane injection	$60–$150 DIY, $400–$900 pro
Widening, needs restraint	Stitching or carbon fiber	$500+ per crack
Slab broken into many pieces	Stop repairing. Replace	$4–$8 / sq ft plus tear-out

The mistake almost everybody makes

Here's our one strong opinion: most failed crack repairs failed because nobody found the water.

Concrete cracks for four reasons — shrinkage as it cures, thermal movement, soil movement under it, and overload. Three of those four are made dramatically worse by water going where it shouldn't. A downspout discharging two feet from the slab, a grade that slopes toward the house, an irrigation head soaking one corner every morning for six years, a sprinkler-fed void that quietly washed the base out from under the apron.

Fixing that costs a $14 downspout extension and an hour with a shovel. Ignoring it means you'll be back in this article in three years wondering why the polyurethane didn't hold.

When you shouldn't hire anyone

Plainly: a stable hairline crack does not need a contractor. Neither does a straightforward leaking crack in a poured basement wall that a $90 injection kit will handle. Neither does a control joint that's just collecting grit and needs a bead of polyurea.

Call a professional when the crack is wider than a quarter inch, when the sides are offset, when it's stair-stepping through a block wall, when it's growing between your pencil marks, or when doors have started sticking and floors have started sloping. Those are structural signals and they want an engineer's eye before anyone sells you a repair.

And if a slab is cracked in half a dozen places with spalling across the surface, stop buying tubes of anything. That slab has told you what it wants. Repair math stops working somewhere around a third of the replacement cost — the deeper version of that decision is in our concrete driveway repair guide.

Bottom line

Measure the width, check for offset, mark it and watch it. Static hairlines get sealant. Working cracks get routed and filled flexible. Structural cracks get epoxy. Leaks get polyurethane. And every single one of them gets a look at where the water is going first.

Pharr Elite Concrete does concrete repair, crack work, and resurfacing along with new slabs and foundations and driveways across Pharr and the Pharr area. Send a photo with something for scale next to the crack and we'll tell you which of the five methods applies, including the times the answer is a hardware-store tube and no invoice. Call (844) 511-2320.