Standard cement-based tile grout is not one hundred percent waterproof; rather, it is porous by nature and will absorb moisture, humidity, and liquids over time if left unprotected. While certain specialized epoxy or pre-mixed urethane grouts offer near-impermeable waterproof qualities and high chemical resistance, conventional cement grouts require a dedicated penetrating sealer to shed water and resist staining. Even with a quality sealer applied, constant standing water or high moisture exposure in showers can gradually penetrate porous grout lines, making proper waterproofing membranes beneath the tile installation essential to protect subfloors and wall framing.
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