And yes, it is expensive (it will vary, obviously, but to give you an idea, we were recently quoted $7,000 to seal a 1500 sq. ft. basement), but a good investment in the long-run
I have an agent in my office from Michigan and he had explained to me the process for Sealing the Exterior Perimiter Walls of the basement so as to protect from water intrusion. The process involved digging up the area around the walls and sealing the surface. The process may be expensive, I would contact a few people who specialize in basement water protection and get quotes. The warranty on my agents basement was for 20 years I believe. I think by doing some research, you may be able to learn more and find a good solution.
Century 21 Infinity
Exterior solution: Perimeter sealing, or perimeter drain systems that direct water away from the house so it never enters the basement. I have heard people refer to exterior perimeter drain systems as "exterior french drains" as opposed to "interior french drains". I have also been told that it is incorrect to refer to these exterior draining systems as "exterior french drains."
Sales Associate, PNJP
973-228-1000 ext 132