Written and reviewed by the Apolodor LTD concrete repair team

Some cracks only need sealing to keep water out. Others have split a slab or wall into separate pieces that now move independently, with one side stepping or rocking against the other. Filling those cracks will not stop that movement. They need to be tied back together, and that is what crack stitching does.

This guide explains what crack stitching is, when it is the right repair, when it is not, and how it is carried out. It also explains how we decide whether a crack needs stitching at Apolodor LTD, because choosing the right repair matters as much as carrying it out well.

Quick answer: Crack stitching restores continuity across a crack by installing bonded reinforcement, usually deformed steel, stainless steel or fibre-reinforced polymer bars, in slots or holes cut across the crack and fixed with epoxy resin or high-strength repair mortar. It should only be used once the cause of cracking has been dealt with and the crack is dormant, and it is often combined with crack injection.

What Is Crack Stitching?

Concrete is strong in compression but weak in tension. Once a crack has formed, the concrete on either side can no longer transfer tensile forces across it. Stitching bridges the crack with short lengths of reinforcement, anchored into sound concrete on each side, so the element behaves as one piece again.

Stitches are normally installed at regular intervals along the crack, with lengths and positions varied so that the forces are not all transferred into a single line of concrete, which could simply cause a new crack to form alongside the old one.

When Is Crack Stitching Used?

• Ground-bearing slabs where a crack has created a step or allows sections to rock under traffic, such as warehouse floors and yard slabs
• Walls where cracking has divided the wall into sections that need to act together
• Pavements, ramps and hardstandings where cracks are widening under repeated loading
• Structural elements where an engineer has designed stitching to restore tensile capacity across the crack

On industrial floors, stitching is often part of a wider repair programme. When repairing warehouse concrete floors, stitching usually sits alongside joint arris repairs and surface work.

When Should Crack Stitching Not Be Used?

Stitching makes a crack rigid. If the forces that caused the crack are still at work, the concrete will crack again, usually next to the stitches. This is why we confirm a crack is dormant before we recommend stitching it. It is not the right repair for:

• Active cracks where movement is ongoing. Establishing whether a concrete crack is active or dormant always comes first
• Cracks caused by reinforcement corrosion, where the answer is fixing the concrete around exposed rebar and treating the steel
• Expansion cracking from alkali-silica reaction, where the concrete is still growing
• Cracks that are meant to be joints, where the concrete needs to keep moving

How Is Crack Stitching Carried Out?

Step 1: Assess the Crack

The crack is recorded, measured and, where needed, monitored to confirm it is dormant. For structural elements, a structural engineer specifies the size, spacing, length and type of stitch.

Step 2: Set Out the Stitches

Stitch positions are marked along the crack, avoiding existing reinforcement where possible. A covermeter is often used to locate bars before cutting or drilling.

Step 3: Cut Slots or Drill Holes

Slots are cut across the crack with a wall chaser or saw, or holes are drilled at an angle across it, to the depth and length specified.

Step 4: Clean the Slots

All dust and debris are removed so the resin or mortar can bond fully to the concrete.

Step 5: Install the Stitches

The slot is partly filled with epoxy resin or high-strength repair mortar, the bar is pressed in, and the slot is filled flush. The bar must be fully surrounded and protected by the bonding material.

Step 6: Seal or Inject the Crack

The crack itself is usually injected with resin or sealed, either before or after stitching, to keep water out and restore contact between the faces. The right crack injection technique depends on crack width, moisture and whether any movement remains.

Step 7: Make Good the Surface

Slots are finished flush, and on floors the surface may be ground and coated so the repair is barely visible.

Crack Stitching vs Crack Injection

Injection fills the crack and, with epoxy resin, can bond the faces back together. Stitching adds reinforcement across the crack. Injection alone is often enough for fine, dormant cracks. Stitching becomes necessary when the crack is wider, when the two sides need mechanical connection, or when an engineer requires tensile capacity to be restored. Many repairs use both.

How Apolodor LTD Approaches Crack Stitching

We only stitch cracks once we understand what caused them and are confident the movement has stopped. Where the element is structural, we work to an engineer’s design for the size, spacing and length of the stitches.

On floors and walls in use, we plan the work to keep disruption low, combine stitching with injection where the crack also needs sealing, and finish the surface so the repair is barely visible.

Cities and Towns We Serve

We assess and stitch cracked slabs and walls through our concrete repair services in:

• London
• Manchester
• Birmingham
• Liverpool
• Leeds
• Nottingham
• Bristol
• Brighton
• Cardiff
• Plymouth
• Luton
• Reading
• Norwich
• Swindon
• Portsmouth
• Oxford
• Ipswich
• Maidstone
• Cambridge
• Southampton
• Slough
• Warrington
• Sheffield
• Leicester
• Coventry
• Milton Keynes
• Northampton
• Derby
• Stoke-on-Trent
• Wolverhampton
• Hull
• Exeter
• Gloucester
• Sunderland
• York
• Peterborough
• Chelmsford
• Newcastle
• Bradford
• Bournemouth
• Swansea
• Newport
• Middlesbrough
• Preston
• Blackpool
• Bolton
• Stockport
• Huddersfield
• Lincoln
• Worcester
• Colchester
• Canterbury

Key Takeaways

• Crack stitching ties cracked concrete back together with bonded reinforcement
• It suits dormant cracks that have separated a slab or wall into independent sections
• It should not be used on active cracks, corrosion cracking or ASR expansion
• Stitches are staggered to avoid creating a new line of weakness
• It is often combined with crack injection and surface repair

Frequently Asked Questions

Does crack stitching stop a crack from moving?

It restrains movement across the crack, but if the underlying cause is still active, new cracks can form nearby. The cause must be dealt with first.

Will the stitches be visible?

They can be set below the surface and finished flush, so on most floors and walls the repair is barely noticeable once complete.

Is crack stitching a structural repair?

It can be. On structural elements, an engineer designs the stitching to restore the capacity needed across the crack.

Talk to Our Team

Apolodor LTD assesses and repairs cracked concrete slabs and walls across the UK, including crack stitching and injection. Call 07808 709670 or contact us here.