How Crack Injection Works: From Drilling to Sealing

Crack injection is one of the most reliable ways to seal leaks and repair cracked concrete — but only when each step is done correctly. Here is how a professional injection job actually unfolds.

Step 1: Assess the crack

Before any drilling, the crack is examined. Is it active (still moving) or dormant? Is it dry, damp or actively leaking? How wide and how deep is it? These answers decide the resin (epoxy for strength, polyurethane for water and movement) and the packers.

Step 2: Set out the injection holes

Holes are drilled at roughly a 45° angle so that they intersect the crack at depth rather than just at the surface. They are staggered along alternate sides of the crack in a zig-zag pattern, typically spaced at a distance similar to the wall thickness. This geometry ensures the resin reaches the full cross-section of the crack.

Step 3: Fit the packers

A packer (or injection port) is inserted into each drilled hole. Mechanical packers expand a rubber sleeve to grip the hole and seal it, while drive-in plastic packers are hammered in and held by flexible lamellae. For thin slabs or hairline cracks where drilling is undesirable, surface-mounted packers are glued directly over the crack.

Step 4: Inject

The resin is pumped through the packers under pressure using an injection machine. Two principles matter here:

• Work from the bottom up on a vertical crack so resin displaces water and air ahead of it.
• Watch for resin at the next packer. When it appears, that section is full — move up to the next port.

Pressure is increased gradually. Too little and the resin won’t penetrate; too much and you risk widening the crack.

Step 5: Let it cure, then finish

Once the resin has reacted and set, the packers are removed (single-use packers are designed for clean same-day extraction) and the holes are patched flush. The surface can then be finished to match the surroundings.

Common mistakes to avoid

• Spacing packers too far apart, leaving unsealed gaps in the crack.
• Injecting top-down, which traps water and creates voids.
• Rushing the cure before removing packers.
• Using the wrong resin — epoxy in a moving, wet joint will simply crack again.

The tools behind the job

A successful injection relies on three things working together: the right resin, the right packers for the substrate, and an injection machine capable of the required pressure. Get all three matched to the crack and you have a repair that lasts.

Want help specifying packers and a pump for an upcoming job? Message us on WhatsApp and we will put together a recommendation.