A drainage groove is an indentation in concrete that allows water to drain away from a foundation or into a drainage system.When concrete is installed, drainage grooves are often formed before the concrete dries. However, if you determine you need drainage grooves after the concrete hardens you can install them with a walk-behind concrete saw and a bit of mortar.
Snap a chalk line over the concrete where you want the center of the drainage groove. Measure to the left and to the right of the chalk line 2 inches and snap two additional chalk lines. The outside lines indicate where the concrete should be cut.
Place the tip of a walk-behind concrete saw blade over the center of one line. Turn on the saw blade and slowly allow the cutter to enter the concrete. The blades have a predetermined depth of 2 inches. Walk behind the concrete cutter. Watch the blade to ensure it stays on the line. Repeat the process with the second line.
Remove the concrete with a sledgehammer and a shovel.
Mix new mortar in a wheelbarrow and pour concrete into the trench you cut.
Create a groove in the new mortar with a round-nosed trowel. Make sure the groove is at least 1¾ inches deep and at least 3 inches wide. Extend the groove the length of the fresh mortar. Allow at least 48 hours' drying time.