Concrete Stitching

Sealing versus holding

There are two separate jobs a crack repair might need to do, and it matters which one you are buying.

Sealing stops water. Polyurethane injection fills the void through the full thickness of the wall and cures flexible, and for the ordinary shrinkage cracks in poured foundations that is the complete and permanent answer.

Holding stops movement. It requires physical reinforcement spanning the crack, capable of carrying tension across it, so the two sides cannot pull further apart.

A moving crack that is only sealed will leak again. The resin is elastic but it is not structural, and continued seasonal movement will eventually break the seal or simply open new fractures alongside it. That is why a homeowner sometimes tells us a crack “was already fixed once”. It was sealed when it needed to be held.

What stitching is

Stitching runs reinforcement perpendicular across a crack at engineered spacing, so the wall behaves as one piece again.

Steel staple stitching. Slots are cut across the crack and heavy steel staples are set into them in high-strength non-shrink grout. Each staple is a mechanical tie carrying tension across the crack. It is the traditional method and it is well suited to wide cracks, displaced cracks, and thick walls where there is depth to key into.

Carbon fibre stitching. Carbon fibre straps are surface-bonded across the crack with structural epoxy. Carbon fibre has exceptional tensile strength for its thickness, which means the repair adds almost nothing to the wall’s profile: valuable when the basement is being finished, or on a floor slab that has to stay flat.

Once movement is arrested, the crack itself is injected so the repair is watertight as well as structurally sound. Both jobs get done, in the right order.

Reading the crack

Not every crack needs this. Most do not. The characteristics that point toward stitching:

• Width beyond about 6 mm. Wider cracks generally indicate genuine movement rather than curing shrinkage.
• Displacement. Run a hand across the crack. If one side sits proud of the other, the wall has moved out of plane and something is driving it.
• Horizontal orientation. Horizontal cracks in a foundation wall usually mean lateral soil pressure. These deserve a careful look, and sometimes engineering input.
• Demonstrated growth. If you marked a crack a year ago and it has passed the mark, it is active.
• Stair-stepping through block. In concrete block foundations, cracking that steps diagonally through mortar joints signals differential movement of the wall.

Where stitching is not enough

We would rather turn work down than sell you something that will not hold.

A bowing wall is a load problem. The soil outside is exerting more lateral pressure than the wall can carry, and it is deflecting inward. Stitching a crack in a bowing wall leaves the load exactly where it was. That situation needs the pressure relieved, usually exterior excavation and drainage, plus proper lateral reinforcement designed by an engineer.

Ongoing footing settlement is a soil problem. If the ground beneath the footing is still consolidating, any repair to the wall above will crack again in the same place. The footing has to be stabilised first.

We will tell you which of these you have.