Contrary to popular belief, ceramic tile and grout, by themselves are not waterproof. Water can penetrate through cement-based grout and work its way through the substrate. To prevent water damage, you must install a waterproof membrane just below the tile bonding mortar as close to the tile as possible.Click to see full answer. In this way, can water leak through tile grout?Cracks in grout can be source of water leaks: The Weekly Fix. If you see stains on the ceiling below your bathroom, don’t assume it’s from a leaking water or drain pipe. This tile needs periodic maintenance; cracks can develop in the grout between the tiles, allowing moisture to seep through.One may also ask, how long before grout is waterproof? Most cement-based grouts require a cure time of 48 to 72 hours before applying a penetrating sealer. After sealing, wait a minimum of 24 hours before using the shower; some products may recommend three days instead. Beside this, do you need to waterproof grout? Why you need grout sealer As a result, if you don’t seal your grout, it will absorb water, bacteria and stains. Adding a grout sealer protects your grout so it’s waterproof and will repel moisture and germs. Sealing the grout helps prolong the look, texture and consistency of your grout and it prevents mildew and mold.Can shower water leak through grout?ANSWER. ANSWER – If water from your shower is leaking into a crawl space the problem is not the cementitious grout joints. There has to be an underlying problem with the shower pan’s waterproof membrane. The proper way to fix this problem is to remove at least the shower pan and reinstall it correctly.