When structural cracks appear in concrete—particularly in load-bearing walls, slabs, and footings—it’s a red flag that signals underlying movement or stress in the structure. Left untreated, these cracks can expand, compromise structural integrity, and lead to costly consequences. One of the most robust, engineer-backed methods for permanent crack remediation is crack lock stitching.

At TruBond Concrete Repairs, we’ve seen firsthand how crack lock systems restore strength, prevent further movement, and serve as a long-term solution across strata, commercial, and industrial settings. This blog breaks down how crack lock stitching works, when to use it, and why pairing it with epoxy injection is often the gold standard in structural crack repair.

What Is Crack Lock Stitching?

Crack lock stitching is a mechanical reinforcement method used to structurally repair and stabilize concrete cracks. It involves cutting perpendicular channels across the crack, inserting high-strength composite or steel reinforcement (typically carbon fiber), and securing it in place with a structural epoxy resin.

Where epoxy injection alone may fill and bond a crack chemically, crack lock stitching adds a mechanical interlock across the fracture line—bridging the crack with reinforcement that actively resists future movement.

This makes it ideal for:

Load-bearing walls with visible movement or step cracks
Retaining walls and suspended slabs with cyclic loading
Structural elements affected by shrinkage, thermal expansion, or subsidence
Sites requiring engineer-certified structural reinstatement

When Should Crack Lock Stitching Be Used?

Crack lock stitching is typically specified in scenarios where:

Cracks are structural, not cosmetic (typically 1-2mm in width)
Movement has been observed, or there’s risk of future displacement
The area is critical to structural stability or safety compliance
Epoxy injection alone may not sufficiently prevent reopening under load

It’s commonly used in tandem with other structural remediation methods on:

Tilt-up panel buildings
Basement and retaining walls
Carpark slabs and podiums
Precast panel joints
Load-bearing masonry in older buildings

How It Works: The Engineering Explained

The crack lock system is designed to restore tensile strength and provide a mechanical bond across the crack—something epoxy injection cannot achieve on its own.

Concrete is strong in compression but weak in tension. When tensile forces exceed what the concrete can handle—due to settlement, flexural loads, thermal stresses, or poor construction practices—cracks form.

Crack locks restore performance through three key engineering principles:

Tensile Bridging – The reinforcement bars (usually carbon fiber or steel) absorb tensile forces, preventing the crack from expanding further or reopening.
Shear Transfer – By spanning across the crack, the embedded stitch transfers shear loads from one side of the concrete to the other, preventing vertical or diagonal displacement.
Load Distribution – Instead of the crack tip bearing all the stress, the reinforcement spreads the load across a broader area, reducing localized failure risk.

These systems have been tested to resist over 4,000 lbs (approx. 18kN) of pull force (Rhino Carbon Fiber Crack Lock®), ensuring reliable performance in critical areas.

The Installation Process (Step-by-Step)

At TruBond Concrete Repairs, we follow a methodical, engineer-aligned process to ensure optimal installation and performance:

Crack Assessment & Mapping
- We assess crack patterns, widths, locations, and movement history.
- Engineers or structural consultants may specify the frequency and depth of stitching.
Chase Cutting
- Horizontal chases are cut perpendicular to the crack at 200–400mm spacing, depending on load and crack behavior.
Crack Cleaning
- Loose concrete and debris are removed from the chase and crack using compressed air and wire brushes.
Stitch Placement
- Crack locks (carbon fiber or helical stainless steel bars) are inserted into the chase, spanning across the crack.
Epoxy Bonding
- High-strength structural epoxy is injected or troweled into the chase to fully encapsulate the reinforcement and fill microvoids.
Finishing & Surface Restoration
- Once cured, the surface is patched flush with surrounding concrete, becoming invisible after application of coloured sealer, epoxy etc.

*Getting ready to place the crack locks in the chased element*

Why Combine Crack Locks with Epoxy Injection?

Epoxy injection is the go-to method for many structural cracks—and for good reason. It bonds the crack internally, restores monolithic behavior, and seals against moisture ingress.

But here’s where epoxy alone may fall short:

It relies purely on adhesion—and tensile strength between concrete and epoxy can deteriorate over time
Epoxied cracks can reopen under cyclical load or thermal movement
It does not mechanically reinforce the area across the crack

By adding crack lock stitching:

You physically prevent movement across the crack
Tensile and shear forces are redistributed, not concentrated at the crack line
The epoxy acts as both a bonding and bedding medium, while the stitch adds structural resilience

Think of it like bone fracture repair: epoxy is the glue, but the crack lock is the internal splint.

Together, they offer a hybrid repair—chemical and mechanical—that is unmatched in durability and reliability.

Additional Use Cases

Crack lock stitching is especially valuable in the following scenarios:

Strata and Multi-Residential Buildings: Hairline cracks in tilt-up or masonry walls can be deceptive. If left untreated, they can propagate. Crack stitching ensures strata managers avoid costly litigation and ensures compliance with engineering reports.
Heritage Buildings: Where demolition or invasive repairs are not permitted, low-profile stitching provides a discreet reinforcement method.
Flood-Prone Areas: Carbon fiber stitch locks are corrosion-proof, making them ideal for basement walls, underground garages, and sea-adjacent structures.
Industrial Settings: Forklift and heavy vehicle zones with slab movement benefit from the added mechanical strength.

Common Misconceptions

🔹 "It’s just an expensive epoxy job."
Incorrect. Crack locks introduce a mechanical element to the repair that epoxy alone cannot replicate.

🔹 "If the crack doesn’t move, it doesn’t need stitching."
Even non-active cracks can destabilize under future loading. Prevention is far more cost-effective than re-repairing failed epoxy.

🔹 "It’s overkill for hairline cracks."
Hairline cracks that span load-bearing areas are high-risk. Stitching offers long-term peace of mind and engineer-signoff.

Real-World Example

Case Study: Warehouse Slab Strengthening, Vaudreuil-Dorion, Quebec

In a project documented by Rhino Carbon Fiber, dynamic cracking was identified in an 8-inch thick warehouse concrete slab subjected to heavy equipment loads and soil movement.

The repair involved:

Installing Rhino Carbon Fiber Crack Lock® stitches every 610 mm across the cracks
Using structural epoxy to encapsulate each stitch
Surface refinishing to restore load transfer capability

After installation, the slab was tested by repeatedly driving a 35,700 kg (78,682 lb) excavator over the area. No further cracking or movement was observed post-repair, validating the strength and durability of the crack lock method.

(Source: Rhino Carbon Fiber Case Study)

Benefits Summary

✅ Restores full structural integrity
✅ Adds a mechanical interlock—beyond epoxy bonding
✅ Corrosion-resistant materials (ideal for wet or saline environments)
✅ Minimal surface impact—no need for demolition
✅ Compatible with epoxy injection for a superior hybrid repair
✅ Fast installation, with low site disruption
✅ Engineer-compliant and certifiable

Why Choose TruBond Concrete Repairs?

At TruBond, we understand that not all cracks are created equal. Our repair recommendations are based on structural context—not guesswork. We partner with engineers to specify the right stitch type, spacing, and epoxy system for your specific job.

Whether you're a strata manager dealing with facade cracks, a builder working on a rectification schedule, or an engineer needing ITP-compliant implementation—we deliver repair strategies that stand the test of time.

✅ Fully trained in Rhino and Ardex crack lock systems
✅ Engineering liaison available for certification
✅ All repairs documented with before/after reports and ITPs

We don’t just fix cracks. We future-proof structures.

Crack lock stitching for structural crack remediation: How it works and when to use it