I've been searching for folks who have reported the same problem as mine, but have not yet been able to find it. I figured I'd throw it out there to the masters (you guys) and see if someone has some suggestions for me.
We just completed our first winter in our new home, and the basement flooded twice. When I say flood, it only got about 1/2 cm deep anywhere and mostly seems to have wicked along the studs that lay flat against the concrete. Half of the basement is finished, and half is not, and the flooding was really only evident in the unfinished side (having passed under the flooring in the finished side). The second time it flooded, the flooring (hardwood) in the finished side was affected, and you can really feel the ridges of the wood.
I think we have determined the cause, but haven't yet figured out a solution. Outside, there is a set of stairs which goes down from ground level about 6 feet where a door opens into the basement. At the outside landing of these stairs, there's a drain. This winter, we had a lot of freezing and melting, and what we found was that the drain at the bottom of the stairs had been covered in a layer of ice, and meltwater pooled in the stairway landing until it got high enough to get in under the door. Though we never witnessed it coming in, we found some dirt and debris leading from the door threshold, and on the hardwood in that area. As far as we can tell, the water then made it's way through the floor down to the the concrete floor, where it pooled, and was channeled along the studs where it was visible in the unfinished area. (The hardwood sits on top of a network of studs, with about an inch gap of airspace between the hardwood and the concrete.
One evening it was raining really hard, so I checked the stair landing and sure enough, there was about 3 inches of water there, so I stayed there bailing it out (during which time the rain thankfully stopped). While bailing, I would reach into the (freezing cold) drain and pull out leaf debris and a bit of mud. I have gone back in drier times and checked - the drain is simple a hole drilled in the landing at the bottom of the stairs, and opens into gravel. There is NOT a pipe of any kind - essentially a french drain. I have sat there with a hose and sprayed water into the hole for about 10 minutes nonstop, and there was never a sign of overflowing. This made me think that it was the combination of an iced-over drain and heavy rain/snow melt that is the problem.
So, from all of this, I think my problem comes down to ensuring that:
1) that drain never gets frozen over, and/or
2) that drain never gets choced out by leaves, silt or any other debris.
I think I can manage keeping it clear, but it hardly seems like a solution. It means that I could never go anywhere in winter for fear that the drain will become blocked.
Can anyone offer any potential solutions? Our house is only 16 years old, and (to my eye) seems well built, save this problem. Is this a structural flaw? I've seen basements with stairs like this before, so there has to be something else to it. I really want to do some insulating down there, but am holding off doing anything until I figure out how to keep it dry.
Cheers - thanks for reading!