Our garage door, pictured below, is right on a sidewalk that slopes downward slightly as it moves past the garage. The result is that one side of the garage door is 4 inches below grade while the other side is 1 inch above grade. There is no drain. A previous owner attempted to keep water out by pouring the cement bump right at the door you see in the picture below to force water to run past the garage door. The problem is that the bump is cracked and does not form a seal with the garage do, so a little water (not to mention draft) still gets into the garage when it rains.
I'm considering repouring the bump, ensuring it is more flush with the garage door, and adding weather stripping. What do you guys recommend? Alternatives? Is it worth considering some type of drain?
Best Answer
@ArchonOSX's answer is good, as long as the local drainage is good enough. If not, I'd install a trench drain that extends further down the slope to where it can discharge back onto the sidewalk, but that depends on the situation.
I'm guessing the door is 8' wide, and the sidewalk falls 5" across it, which means the sidewalk has about 1/2" per foot pitch.
Let's say you install a level trench in front of the door, starting 1" below the door and with a depth of 4" (with a grate on top). At the downhill end of the door the trench bottom will be 4" below the sidewalk.
Then you have to get rid of the water. Drains should have 1/8" per foot pitch, so the sidewalk will fall 3/8" per foot faster than the drain. So, it will take another 11 feet before the sidewalk is below the bottom of the drain. If you have that kind of space you can just extend the trench to that point and then turn it back to the sidewalk.
If not, improvise.