The work done before the tile installation needs to be precise and effective to ensure any water that makes it past the tile and grout goes down the drain and not into your walls and subfloor. This can cause major damage to your home! Most people and sadly even some contractors believe that tile and grout are waterproof, however, that is not the case. If steps are skipped during the preparation of the shower and waterproofing, you could find yourself with a leaking shower.