Basement problem due to neighbor
I'm having seepage in our basement and I think I have it narrowed down to our neighbor. Basically, the water seeps in along one wall only. It's not a lot, but I definitely need to do something about it before I finish the basement. I checked during a heavy rain and the ground along the exterior wall was dry. We have fairly large overhangs in the roof and the downspouts are directed away from the house using those black plastic drain pipes.
Well, the neighbor's house is approximately 15 feet away from ours and sits a couple of feet higher. It's downspout is pointed directly at the basement wall that is seeping. I thought I would offer to reroute the spout away by using the plastic drain pipes again, but their gutters are pretty trashed and so water drips along the whole side of their house. As a result, I can't just redirect the downspout to solve the problem.
Any ideas on what I might be able to do to solve this? Is there some kind of barrier that I can install to prevent their water from seeping onto our property? I thought maybe a french drain near the property line to capture the water to a depth of about 3 to 4 feet. Would that be sufficient or would I need to go deeper?
If you have any suggestions, they would be greatly appreciated. I have spent way too much time this winter drying the basement.
Thanks in advance.