There is simply no point in finishing your basement if it leaks water. Covering up a water problem will only defer the damage from mold, mildew, and rot. The time to fix water-incursion problems is before they’re covered up with insulation and drywall.
Almost all the basement-water problems I’ve encountered in 30 years of remodeling and house construction are the result of surface water (rainfall and runoff) and bad drainage. These problems can almost always be fixed by making sure water drains away from the house foundation.You can often do this work yourself.
If the surface-water drainage is fine, but you still have leaks, ground water may be the reason.Ground water is subterranean, moving through the soil from areas of high to low water pressure. Leaks caused by ground water require removing or redirecting the water from around the foundation with drain tile and a sump pit and pump. In my area, these are often installed in new houses at the time they’re built because it’s easy to do then.
New and old houses can be retrofitted with drain tile and sump, too. Drain tile (which today is usually perforated plastic pipe rather than clay tile) can be laid inside or outside. The sump pit and pump are usually installed inside. An inside installation involves cutting out the floor around the perimeter of the basement about 1 ft. to 1-1/2 ft. in from the wall, excavating enough dirt to drop in some gravel, the drain tile, and a sump pit, and then pouring a new floor over the gravel.Water seeping around or under the foundation and floor flows to the lowest point (the gravel and drain tile), drains to the sump pit, and is pumped away.
Installing drain tile and sump systems is an arduous task and requires some special skills and tools, so I recommend you hire it done. If you suspect ground-water problems, start by consulting a specialist or a knowledgeable builder... we recommend us!