How to Fix Cracked Concrete – Driveways, Patios & Foundations

fix cracked concrete finished result — clean, professional look — Concrete cracks sealed — smoother, protected surface.

Patching Cracked Sidewalks and Patios

Most non-structural cracks can be repaired with polyurethane sealant or concrete patch compound. Wider or moving cracks benefit from backer rod and flexible sealants; structural cracks may call for epoxy injection or pro evaluation. Clean the area, widen the crack slightly, fill properly, and seal to prevent moisture damage.

Identify crack type: hairline, non-structural, or structural.
Clean out debris and dust for better adhesion.
Widen V-groove on deep cracks to accept filler.
Use polyurethane sealant for flexible outdoor joints.
Seal the slab after curing to reduce future cracking.

Installation Snapshot (Project Planner)

Skill: Beginner to Intermediate
Time: 45 minutes – half day depending on length/width
Cost: $10–$60 in materials
Savings vs Pro: ~$150–$400+
Pro Tip: Repair when the slab is dry and temps are moderate; extreme heat or cold, and moisture, weakens adhesion.

Tools & Materials for Concrete Crack Filling

Tools

Wire brush and stiff broom
Chisel or angle grinder with crack-cleaning wheel
Caulk gun (for sealants)
Putty/finishing knife
Shop vacuum
Gloves, eye protection

Materials

Polyurethane concrete crack sealant or patch compound
Backer rod (for wide/deep joints)
Concrete cleaner/degreaser
Concrete sealer (penetrating or film-forming)
Epoxy injection kit (for structural cracks; optional)

How Hard Is It to Fix a Concrete Patio or Sidewalk Crack?

Surface cracks are straightforward if you can clean and prep properly; success hinges on adhesion and flexibility. Hairline cracks may only need a thin, flowable filler, while wider cracks benefit from backer rod and polyurethane sealant. Epoxy is stronger for structural issues but costs more and requires careful mixing and injection. If cracks keep growing or you see settlement, consult a pro to address underlying causes.

Step-by-Step: Epoxy and Sealant Concrete Crack Repair

Step 1 — Diagnose the Crack

Note length, width, and whether edges are level. Hairline and non-structural cracks are safe DIY. If the slab is heaving, sinking, or the crack is wide and growing, plan for a professional evaluation.

Inspecting a concrete crack for width and movement — Diagnosis guides filler choice and method.

Step 2 — Clean and Widen for Adhesion

Wire-brush loose material, then V-groove deep cracks with a chisel or grinder. Vacuum dust and wash with cleaner; let it dry fully. Clean walls and edges are key to long-lasting repairs.

Cleaning and V-grooving a concrete crack before filling — Prep is 80% of a durable repair.

Step 3 — Fill with the Right Product

Install backer rod if the crack is wider than 1/4″, then apply polyurethane sealant or patch compound, working it into the joint. For structural cracks, follow an epoxy injection kit’s ports and timing closely. Avoid overfilling — level with a putty knife before it skins.

Applying polyurethane crack sealant over backer rod — Backer rod controls depth and saves material.

Step 4 — Cure and Seal the Surface

Respect cure times on the label; foot traffic too soon can tear the repair. After curing, apply a penetrating or film-forming concrete sealer to keep water and salts out. Reseal every few years, especially in harsh climates.

Sealing a repaired concrete slab with a roller — Sealing protects the repair and surrounding slab.

Pro Tips to Patch Cracked Sidewalk & Patio Repairs

Repair on a dry day; moisture in the crack ruins adhesion.
Use backer rod to set a proper sealant depth-to-width ratio (~1:2).
Feather patch edges to avoid trip lips or water pooling.
Color-match sand or tint only after test patches dry.
Control joints: cut or clean them so cracks follow those lines, not across the slab.
Seal annually in freeze-thaw climates to limit spalling.
If movement continues, investigate drainage and subgrade issues.

FAQs: Epoxy Concrete Repair & Crack Fillers

What’s the best filler for small cracks? Concrete patch compound or polyurethane sealant.

Can I use concrete mix for crack repair? Not ideal. It doesn’t bond well — use crack-specific fillers.

Do I need to seal concrete after repair? Yes, sealing helps prevent moisture and new cracks.

What causes concrete to crack? Common causes include settling, temperature changes, and moisture.

Can I fix cracks in cold weather? Only use cold-weather formulas and wait for temps above freezing.

Should I widen the crack before patching? Slight widening improves adhesion in deep cracks.

Is epoxy better than patch compound? Epoxy is stronger but may cost more — ideal for structural cracks.