Grout Cleaning and Resealing: When to Scrub and When to Replace

Grout discoloration has two very different causes that need different fixes: surface dirt and mildew sitting on top of the grout, or grout that has lost its sealer and is absorbing stains into the material itself. Scrubbing helps the first and does almost nothing for the second.

Diagnose before you clean

• Run a wet finger over the grout line. If water beads up, the sealer is intact and surface cleaning should work.
• If water soaks in immediately and darkens the grout, the sealer has worn off and cleaning alone will not restore the original colour.
• Crumbling, cracked, or missing sections of grout need to be dug out and repointed, not cleaned or resealed over.

Cleaning methods, from mild to aggressive

When to reseal versus replace

If the grout is structurally sound (no cracking or crumbling) but simply absorbs water and stains, cleaning followed by a fresh coat of sealer restores both the look and the protection. If sections are physically breaking down, sealer will not fix that — it needs to be scraped out to a consistent depth and repacked with new grout before any sealing is worth doing.

1. Clean the grout thoroughly and let it dry completely, typically 24-48 hours.
2. Apply a penetrating grout sealer with a small applicator brush or roller, following the joint lines closely.
3. Wipe excess sealer off the tile surface before it dries to avoid a hazy film.
4. Apply a second coat after the first has absorbed, if the product recommends it, for better long-term protection.

How often resealing is actually needed

Most penetrating sealers last 1-2 years in high-traffic or wet areas like bathroom floors and shower surrounds, and up to 3-5 years in lower-moisture areas like a kitchen backsplash. Epoxy grout, increasingly common in new installations, does not need sealing at all since it is non-porous by design.

Repointing badly damaged grout

Use a grout saw or an oscillating tool with a grout removal blade to remove damaged grout to a consistent depth, vacuum out the debris, then apply new grout matching the original colour, working it into the joints with a rubber float and cleaning excess the same way as a new installation.