Grout starts white or light gray and slowly turns dark, dingy, and stained over months of foot traffic, soap scum, and moisture. Cleaning and sealing grout is not glamorous, but it makes tile floors and walls look new again and prevents the mold and mildew that thrive in porous, unsealed grout lines.

How to Clean and Seal Grout

Why Grout Gets Dirty

Cement-based grout is porous. It absorbs water, dirt, grease, soap residue, and mold spores. Every time you mop a floor or take a shower, the grout lines soak up a little more discoloration. Over time, even well-maintained grout looks grimy simply because it has absorbed years of contaminants.

Sealing the grout fills those pores and creates a barrier. But the sealant wears off over time, so periodic cleaning and resealing keeps grout looking fresh.

Cleaning Methods — Mildest to Strongest

Always start with the gentlest method and escalate only if needed. Harsh chemicals can etch tile and damage colored grout.

Baking Soda and Water Paste

Mix baking soda with enough water to form a thick paste. Spread it along the grout lines with an old toothbrush or grout brush. Let it sit for 10 minutes, then scrub and rinse. This works well on light surface discoloration.

Baking Soda and Vinegar

Apply the baking soda paste first, then spray white vinegar over it. The fizzing action lifts dirt from the pores. Scrub with a stiff brush and rinse thoroughly. Do not use vinegar on natural stone tiles — the acid etches marble, travertine, and limestone.

Hydrogen Peroxide

For mold and mildew stains, mix equal parts hydrogen peroxide (3 percent) and water in a spray bottle. Spray directly on the grout, let it sit for 15 minutes, and scrub. Peroxide is a mild bleach that kills mold without the harsh fumes of chlorine bleach.

Oxygen Bleach (OxiClean)

Dissolve oxygen bleach powder in warm water per the label. Pour or spray it on the grout and let it soak for 15 to 30 minutes. Scrub with a brush and rinse. Oxygen bleach is effective on organic stains and safe for colored grout and most tile types.

Chlorine Bleach (Last Resort)

Mix one part bleach to ten parts water. Apply to grout only — avoid getting it on colored tile or metal fixtures. Let it sit for 5 minutes, scrub, and rinse thoroughly. Open windows or run a fan for ventilation. Never mix bleach with vinegar or ammonia-based cleaners.

Steam Cleaner

A handheld steam cleaner blasts grout lines with pressurized steam, loosening dirt without chemicals. This is effective and environmentally friendly but slower than chemical methods for large areas.

Tools for Scrubbing

A stiff nylon grout brush works for small areas. For large floors, a drill-mounted grout brush attachment turns your cordless drill into a power scrubber and saves your knees and elbows.

Avoid metal brushes — they scratch tile and can leave metal deposits in the grout that rust later.

Sealing Grout

Once the grout is clean and completely dry (wait at least 24 hours after deep cleaning), apply a grout sealer to protect it.

Types of sealers:

Penetrating sealers: Soak into the grout and fill the pores from within. They do not change the appearance of the grout and last 3 to 5 years. Best for most applications.
Topical sealers: Sit on the surface and create a visible film. They add a slight sheen and repel stains more aggressively, but they can peel and need more frequent reapplication.

Application:

Ensure the grout is completely dry.
Apply the sealer with an applicator bottle (for precision along grout lines) or a sponge (for large floor areas).
Let the sealer soak in for 5 to 10 minutes.
Wipe excess sealer off the tile surface with a clean, dry cloth. Sealer left on tile can create a hazy film.
Apply a second coat after 30 minutes.
Avoid foot traffic and water for 24 hours.

Maintaining Sealed Grout

Sweep or vacuum tile floors regularly to prevent grit from grinding into grout lines. Mop with a pH-neutral tile cleaner — avoid acidic or highly alkaline cleaners that break down the sealant.

In showers, squeegee the walls after each use. This simple habit dramatically reduces soap scum and mildew buildup.

Reseal grout every 1 to 3 years depending on traffic. Test by dropping water on a grout line — if it beads up, the seal is intact. If it soaks in and darkens the grout, it is time to reseal.

When to Regrout

If the grout is cracked, crumbling, or deeply stained beyond what cleaning can fix, regrout rather than seal. Remove the old grout with a grout removal tool or oscillating multi-tool, clean the joints, and apply fresh grout. Then seal the new grout after it cures.

Clean, sealed grout makes the entire tile surface look better. It is one of the cheapest ways to refresh a kitchen or bathroom without any demolition.