Exterior waterproofing stops water at the outside of your foundation by sealing the walls, installing membranes and drainage boards, and adding or replacing weeping tiles at the footing. Interior waterproofing manages water that has already reached your foundation by capturing it along the inside perimeter and directing it to a sump pump or floor drain. Both approaches are effective when used in the right situations, and in some cases a combination of interior and exterior work offers the best long-term protection.