Concrete Crack Injection: When a Crack Needs It

Concrete repair for parking garages and buildings in Toronto and the GTA.

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In short: concrete crack injection fills a crack from the inside, either to bond the concrete back together or to stop water coming through it. It suits cracks in walls, slabs and columns that an engineer has looked at. It doesn’t fix the reason the crack opened, so the cause comes first.

What is concrete crack injection?

Small ports are set along the crack and the surface is sealed between them. A liquid is then pumped into the ports, one at a time, until it comes out of the next one. When it cures, the crack is full from the back of the concrete to the face.

There are two common materials. Epoxy cures hard and bonds the two sides of the crack, so it is used where the concrete has to carry load again. Polyurethane foams and stays flexible, so it is used to stop leaks in cracks that still move a little.

Repaired sections on a curved concrete wall in the GTA — Concrete repair by Grand Structural Services.

When a crack needs injection

Water is coming through. A wet crack in a garage wall or slab lets in water and road salt, and the rebar inside starts to rust.
The engineer wants the concrete bonded. A structural crack in a column, beam or slab may need epoxy so the member works as one piece again.
The crack is part of a larger repair. On a restoration project, injection is often one line item next to slab, column and wall repairs.

When injection isn’t the answer

If the concrete around the crack is soft, hollow or falling away, the damage goes deeper than the crack. That concrete has to be removed back to sound material and rebuilt. Injecting it would only hide the problem. A crack that keeps growing also points to a cause, such as settlement or overload, that the engineer has to deal with first.

Epoxy or polyurethane?

The engineer decides, based on two questions: does the crack still move, and is water coming through? A dry, stable crack in a structural member usually gets epoxy. A damp or leaking crack that moves with the seasons usually gets polyurethane. Some jobs use both, one after the other.

Concrete wall rebuilt after damaged concrete was removed, a structural concrete repair in the GTA — Concrete repair by Grand Structural Services.

How crack injection is done

Clean the crack and the face of the concrete.
Stop any running water, often with hydraulic cement.
Set the injection ports and seal the surface between them.
Inject from the lowest port up, until the material shows at the next port.
Let it cure, remove the ports and finish the surface.

Crack injection in Toronto garages and buildings

We do concrete crack injection in parking garages and in commercial and industrial buildings across Toronto and the GTA, usually as part of a larger concrete repair job. We work to the engineer’s spec and choice of material. We don’t take homeowner basement crack repairs.

Questions people ask

Is crack injection a permanent repair?

It is when the right material goes into the right crack. The engineer picks it based on whether the crack still moves and whether water is coming through.