Short answer
Standard cement grout (sanded or unsanded) should be sealed. It's porous and stains easily, especially on floors, showers and backsplashes. Epoxy grout and many high-performance grouts don't need sealing; check the bag. Seal once the grout has cured (often 2–3 days, but follow the grout maker), and reseal when water stops beading up. Sealer protects grout from stains. It does not waterproof a shower.
Why seal grout at all?
Cement grout is full of tiny pores. Coffee, cooking oil, soap scum and dirty mop water soak in and darken it. A penetrating sealer fills those pores so spills sit on the surface long enough to wipe away. It also slows down the dark, damp look shower grout gets, and makes cleaning easier.
Which grouts need sealing?
| Grout | Seal it? |
|---|---|
| Sanded / unsanded cement grout | Yes |
| High-performance cement grout | Often not required; check the product |
| Epoxy grout | No |
| Urethane / pre-mixed grout | Usually no |
See grout types explained and epoxy vs cement grout.
How long after grouting?
The grout has to cure first, or the sealer traps moisture and can leave a cloudy or blotchy finish. Many grout makers say to wait around 48–72 hours. Some say longer in cool, damp conditions. Follow the grout bag rather than a general rule. For when you can walk on or shower on new tile, see how long before using new tile.
How often to reseal
Do a simple test: put a few drops of water on the grout. If they bead up, the sealer is working. If the grout darkens within a few minutes, it's time to reseal. Busy shower floors and kitchen backsplashes often need it about once a year. Low-use floors need it less often.
Choosing and applying a sealer
- Penetrating (impregnating) sealers soak in and don't change the look much. They're the usual choice for grout.
- Coating sealers sit on top. They can add sheen but wear and peel, and are rarely the right choice for showers.
- Colour sealers / grout colourants dye and seal at once, which is useful for making stained or patchy grout uniform again.
- Clean the grout thoroughly and let it dry before sealing. Sealer locks in whatever is already there.
- Apply only to the grout (a narrow brush or applicator bottle), and wipe any excess off the tile right away, especially polished stone or glossy tile.
- Natural stone may need its own sealer for the tile too (see natural stone care).
What sealer can't fix
- A leaking shower. Waterproofing is behind the tile, not in the grout (see how showers are waterproofed).
- Cracked or crumbling grout, which needs regrouting (see why grout cracks).
- Pink, orange or black staining that keeps coming back, which usually means moisture or cleaning issues (see grout discolouration).
