I am looking to help a friend repair cracked sunken garage floor. The apron 8" out past where the garage door closes and 8-10" into the garage have cracked and sunk near the inside block walls. I have poured sidewalks, driveways and pads, but never a garage floor. At first, I thought he just wanted the outside replaced, no problem, but inside. I am not sure how to cut the floor at the block wall.