I have converted garage with door way about 4 inches below the driveway. Previous owner left this issue for me. My questions is i want to cut into concrete to create drainage system, french drain with metal grating. I'm not sure how to handle the doorway. how far away from the entrance do i cut across. Do i need to cut out say a doormat piece of concrete in front of the door so entrance is level. Or just by creating this drainage to run the width of the driving place close enough the doorway(with out change it being below driveway) will resolve my water issue?