Ways to keep basements dry
Condensation problems can be solved by improving ventilation and using air conditioners and dehumidifiers. Eliminating seepage, however, is another matter. If seepage occurs only during heavy rains, the solution could be as simple as extending a downspout so that runoff is directed farther away from foundation walls, or regrading the soil so that it slopes away from the foundation. You can often correct minor seepage from the inside, by coating interior foundation walls with a masonry sealer (either a cement- or tar-based product or a waterproof silicone sealer). As a last (and very expensive) resort, you may have to re-excavate the foundation down to the footings to install perimeter drains and apply new waterproofing.