Smaller Holes and Cracks
Put a dropcloth underneath the wall hole.
Locate the crack causing the leak. Stick the end of a cold chisel into the hole and chip away at it, to expand the hole, and to make the hole the same width at the surface and the bottom. Clean out the hole with a vacuum to remove any dust.
Hammer finishing nails into the crack, every 8 inches. Place an injection port over the nail so that the port hangs.
Mix together your patching epoxy in a small bucket using the instructions on the package. Epoxy generally comes in two parts. Mix together equal amounts of each part.
Cover the hole with the epoxy using a putty knife. Cover the base of the injection ports to hold them in place.
Stick your tube of epoxy filler into your caulk gun. Cut the end off the tube. Press the trigger a few times to get the epoxy flowing. Stick the end of the epoxy filler into the port and inject the epoxy into the hole. Cover the end of the port with the port cap. Do this all the way up the crack. Let the epoxy dry along the crack, then cut off the tips of the ports, flush with the wall.
Clean debris from the hole using a chisel and sledgehammer.
Fill the hole with the larger chunks of debris.
Mix together a bucket of hydraulic cement using the instructions on the packaging.
Put on a pair of latex gloves and pack the hole with the cement by hand, pushing the cement between the large pieces of debris.
Push on the cement using a hand trowel and smooth the cement to the surface of the wall.