How Does Foundation Crack Repair Work? The Process Step by Step

How Does Foundation Crack Repair Work? The Process Step by Step

How does foundation crack repair work? For most cracks, a technician injects epoxy or polyurethane resin into the crack under low pressure — the resin fills the crack from the inside out and hardens into a strong, waterproof seal. The whole job usually takes two to four hours for a single crack, and you can use the room the same day. It is a real repair, not a bandage: when the crack is non-structural, injection restores the wall’s water-tightness and much of its strength.

Not every crack qualifies for injection. The process starts with reading the crack: hairline shrinkage cracks are usually cosmetic, while wide, stair-step, or horizontal cracks can signal movement injection alone will not fix. In Shreveport, where expansive clay swells and shrinks with the seasons, knowing which kind you have is the whole ballgame.

The short version: most foundation crack repairs are a same-day injection job costing a few hundred dollars per crack. Wide or growing cracks need a structural fix like piers first, and then the crack gets sealed. A free inspection identifies the crack type and the right process for it.

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Step 1: Inspection and Diagnosis

Every proper crack repair starts with reading the crack, because the crack pattern is a diagnostic report written by your foundation. The technician measures the crack’s width, maps its direction (vertical, diagonal, horizontal, or stair-step), and checks whether one side has shifted relative to the other. A pencil mark and a date across the crack, checked weeks later, shows whether it is still moving.

Width is the first sorting line. Hairline cracks under about 1/16 inch are usually shrinkage from the concrete curing, and they are mostly a waterproofing concern. Cracks around 1/8 to 1/4 inch deserve attention, especially if they leak. Anything wider than about 1/4 inch, any horizontal crack, or any crack where one side is offset from the other points to structural movement.

In the Shreveport area, the usual suspect behind moving cracks is the expansive clay under Caddo and Bossier Parishes — it swells in wet seasons, shrinks in dry ones, and works on foundation walls year after year.

Step 2: Surface Prep and Port Installation

Once the crack is diagnosed as a good injection candidate, the crew preps the surface. Loose material, paint, and efflorescence (that white powdery residue) get cleaned off so the sealing materials bond to solid concrete. If water is actively flowing through the crack, the crew manages it first.

Next come the injection ports: small plastic nozzles bonded over the crack every 6 to 12 inches along its length. Between the ports, the technician applies a surface seal — usually an epoxy paste — over the face of the crack. This seal is temporary; its job is to keep the injected resin inside the crack under pressure instead of oozing out the front.

Prep quality separates a lasting injection from an early failure. This stage usually takes 30 to 60 minutes for a typical residential crack.

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Step 3: The Injection — Epoxy vs. Polyurethane

Here is the main event. Starting at the lowest port, the technician pumps resin into the crack under low pressure and works upward, port by port. As each section fills, resin appears at the next port up — that is the signal to cap the current port and move along. The resin travels through the full depth of the wall, filling the crack from the inside out.

The two resins do different jobs, and picking the right one matters:

Feature	Epoxy injection	Polyurethane foam injection
What it does	Bonds the concrete back together structurally	Seals out water with a flexible foam
Flexibility	Rigid — very strong but does not flex	Flexible — moves slightly with the wall
Best for	Non-moving structural cracks needing strength	Leaking cracks, cracks that may move slightly
Works in wet cracks	No — needs a dry surface to bond	Yes — reacts with water to expand
Typical cost per crack	$400-$800	$300-$700

In northwest Louisiana, polyurethane is the more common choice because it handles active leaks and tolerates the small seasonal movement our clay soils cause. Epoxy is the pick for structural bonding of a stable, dry crack. Our foundation crack repair services page covers both methods.

Step 4: Curing, Cleanup, and Waterproofing

After injection, the resin needs time to cure. Polyurethane foam sets up in minutes to a few hours; epoxy typically needs several hours to a full day to reach full strength. The crew removes the ports, grinds the surface seal flush, and patches the port spots so the wall looks clean. For interior walls, the repair is paintable once cured.

Curing is not the end of the story if water was the reason you called. An injected crack is sealed, but the water pressure that found the crack is still out there. That is why the final step is often waterproofing: a coating over the repaired area, and — more importantly — making sure gutters, grading, and drainage move water away from the foundation.

Before the crew leaves, ask them to walk you through what was done: which resin was used, how many ports, and what the warranty covers. Reputable crack injection work comes with a written warranty against re-leaking.

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When Injection Is Not Enough: Exterior Excavation

Some cracks cannot be fixed from the inside. If the outside of the wall is badly deteriorated, if water pressure is severe, or if the crack runs through a section of wall that needs structural reinforcement, the crew digs down to the footing on the exterior side. It is the most thorough — and most expensive — way to fix a crack, because it addresses the wall from the water’s side.

The exterior process goes like this: excavate down to the footing along the cracked section, clean the wall, fill and seal the crack from outside, apply a waterproof membrane over the area, install or repair drainage board and a footing drain, then backfill with gravel that drains instead of holding water.

Exterior excavation typically costs $2,000 to $6,000 or more per wall section depending on depth and access. It is usually a two- to four-day job. Most residential cracks never need this, but when a wall is taking on serious water, exterior work is the honest answer.

What Foundation Crack Repair Costs

Here is how the options compare for a typical Shreveport-area home. Most homeowners only ever need the first row.

Repair method	Typical cost range	Timeline	Best for
Polyurethane injection (per crack)	$300-$700	2-4 hours	Leaking or hairline-to-moderate cracks
Epoxy injection (per crack)	$400-$800	3-5 hours	Stable cracks needing structural bond
Exterior excavation (per wall section)	$2,000-$6,000+	2-4 days	Severe water intrusion, deteriorated walls
Piers + crack sealing	$4,000-$12,000+	2-5 days	Cracks caused by ongoing settlement

Watch out for the too-cheap injection quote. Proper injection uses quality resin, enough ports, and real surface prep — a rock-bottom price usually means thinned-out resin, skipped ports, or no warranty. If you want to compare notes, our guide on how to repair a foundation crack covers the homeowner side of the decision.

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When a Crack Means You Need Piers Instead

This is the most important section in this article, because injecting a crack that is still moving is wasted money. Injection seals; it does not stabilize. If the foundation is still settling or shifting, the crack will reopen next to the repair. These are the signs that piers or underpinning need to come first:

• The crack is wider than about 1/4 inch and growing. Measure it, date it, and check it again in a few weeks. Growth means movement.
• Horizontal cracks in the wall. These usually mean lateral soil pressure is pushing the wall inward — a structural problem, not a sealing problem.
• Stair-step cracks in brick or block. The classic signature of differential settlement.
• One side of the crack is offset from the other. Displacement means the wall has actually shifted, not just cracked.
• Doors and windows sticking near the crack. The frame distortion and the crack are symptoms of the same movement.

When these show up, stabilize first with steel push piers or helical piers driven to stable soil, lift the settled section back toward level, and then seal the crack. The piers stop the movement; the injection seals the evidence. Our vertical foundation crack repair guide covers which crack orientations are safe to inject.

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Frequently Asked Questions

How long does foundation crack repair take?

A single crack injection usually takes two to four hours, and you can use the room the same day. Epoxy needs longer to fully cure than polyurethane. Exterior excavation takes two to four days, and piering jobs take two to five days.

Is epoxy or polyurethane better for crack repair?

It depends on the crack. Epoxy bonds concrete back together and is stronger, but it needs a dry, stable crack. Polyurethane expands to seal leaks, works in wet cracks, and flexes slightly with seasonal soil movement. In Louisiana, polyurethane is the more common pick for leaking wall cracks.

How much does it cost to fix a foundation crack?

Injection typically costs $300 to $800 per crack depending on resin, crack length, and access. Exterior excavation runs $2,000 to $6,000 or more per wall section. If settlement is the cause, piers plus sealing run $4,000 to $12,000 or more.

Can I repair a foundation crack myself?

DIY injection kits exist, but they are a gamble. Pros use higher-pressure equipment and better resin, and — more importantly — they diagnose the crack type first. Sealing a structural crack yourself can hide a problem that keeps getting worse behind the patch.

Will the crack come back after injection?

A properly injected, non-moving crack should not reopen — the resin fills the full depth of the wall. But if the foundation is still settling, new cracks can form nearby or the repair can fail.

Do all foundation cracks need repair?

No. Hairline shrinkage cracks that are dry and stable are usually cosmetic and just need monitoring. Cracks that leak, are wider than about 1/8 inch, are growing, or show displacement deserve professional attention.

When does a crack need piers instead of injection?

When the foundation is still moving. Wide or growing cracks, horizontal cracks, stair-step patterns, offset crack faces, and sticking doors near the crack all point to settlement or pressure that injection cannot fix. Stabilize with piers first, then seal the crack.

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Get a Free Foundation Crack Inspection in Shreveport

A crack is your foundation trying to tell you something — the question is whether it is saying “seal me” or “stabilize me.” Our free inspection reads the crack, measures it, checks for movement, and gives you the right process for your situation: injection, exterior waterproofing, or piers first.

Call Pelican Foundation Repair at (318) 585-2003, or visit Pelican Foundation Repair to schedule. We repair foundation cracks across Shreveport and the surrounding parishes — see our service areas list.

Pelican Foundation Repair 6118 Fairfield Ave, Shreveport, LA 71106, USA 318-585-2003 https://foundationrepairshreveport.com/