The surest way to waterproof your basement walls is a full-scale exterior waterproofing solution. It's also the most expensive - often $15,000 to $30,000.
Exterior waterproofing involves excavating all around the house to the full depth of the foundation walls, then installing a waterproof coating or membrane topped by drainage panels. The panels provide an easy path for water to flow down to an exterior French drain at the bottom of your foundation. From there, water flows by gravity - or with the aid of a sump pump - away from your foundation to another part of your property, or into a storm drain.