After the foundation crack has been identified and determined to need repair, the first stage of the repair process is the "drilling".
For HPI or "high pressure injection", a series of 3/8" diameter holes are drilled from the bottom of the crack (starting approx. 1" above the floor) and continue all the way up to the sill plate at the top of the foundation. These holes are drilled along side the crack about 3" to either side at an angle of approx. 45-55 degrees. This is imperative as the "vein" of the crack must be intersected at a depth of approx. 4" into the 8" thick wall. This will ensure optimum Polyurethane Resin penetration at the injection stage.
On average, there will be between 18 and 20 (average spacing of 5-6") injection points on a typical crack. The last step of the drilling stage is to flush out any drilling dust/debris from the holes with water.