My garage is at the bottom of a gently sloping drive which has been covered in tarmac by some previous owners. Originaly the drive was just covered in rough chippings, so any rain water would just soak away.
When it rains heavily, water works it's way under the door and eventualy forms a long lasting puddle over half the area of the floor.
I believe this is cause by two things.
(1) Rain water running down the garage door and onto the garage floor. (2) Rain water being prevented from soaking away through the tarmaced drive.
I have found what would seem to be the ideal solution