Grout and stone or clay tiles look impenetrable, but in fact neither is completely waterproof in their natural, unsealed states. Applying liquid sealant over the grout lines is simple, unless you're installing unsealed tiles. In that case it gets complicated because, if you grout the lines first, it might stain the unsealed tiles; but if you seal the tiles first, it can prevent the grout from setting correctly in the lines. The proper approach is a balancing act of sealing and grouting in multiple layers.
Things You'll Need
- Penetrating tile sealant
- Grout float
Use your paintbrush to apply a layer of penetrating sealant to your newly installed, unsealed tiles before the grout is installed. Brush the sealant on the tile face in a thin, even coat, but don't let it gather or drip in the spaces between the tiles.
Let the sealant dry to the touch (generally an hour). Apply a second coat to the tiles in the same manner.
With your grout float, wipe grout across the tile surface, using the edge of the float to press it into the lines between the tiles. Let the grout sit in the lines for a minute then wipe down the surface with a damp sponge to take up the excess grout. (The sealant on the tile face should prevent it from sticking or staining.)
Let the grout cure for at least two days. Re-apply penetrating sealant over the tiles and the grout lines all at once, using a brush.
Apply a second full coat of sealant to the tiles and grout after the first coat dries.