How to Clean Tile Grout on Floors and Walls

Short answer: Sweep or vacuum, make a paste of baking soda and hydrogen peroxide, work it into the grout lines with a stiff grout brush, leave it ten minutes, scrub, rinse with clean water and dry. For mildew in a shower, spray peroxide and let it sit. For lines that stay dark, use oxygen bleach. Once the grout is clean and dry, seal it, so the next clean is a mop rather than a project.

You need: a grout brush or stiff nylon brush (an old toothbrush for small areas), baking soda, hydrogen peroxide, a spray bottle, a bucket, cloths or a mop, and rubber gloves. For stubborn grout, oxygen bleach powder. Time: an hour for an average bathroom floor, more for a kitchen.

Before you start

Grout is cement, sand and water, and most of it is porous. That is why it stains, and it is also why acids such as vinegar and strong bathroom cleaners wear it away over time. Everything here is alkaline or neutral, so it cleans without eating the grout. Open a window, wear gloves, and if your tile is natural stone such as marble, travertine or slate, skip the baking soda paste and use only a cleaner labeled safe for stone, because anything abrasive or acidic can etch the tile.

Step 1: Sweep and wipe the tile

Vacuum or sweep the floor, then mop with warm water so you are scrubbing grout and not the grit sitting on top of it. On walls, wipe the tile down with a damp cloth. Let the grout stay damp; wet grout takes the paste better.

Step 2: Make the paste

Mix baking soda with enough hydrogen peroxide to make a thick paste, about the texture of toothpaste. Mix small batches, because the peroxide loses strength once it is mixed. For a kitchen floor with greasy grout, add a drop of dish soap.

Step 3: Work it into the grout lines

Spread the paste along the grout lines with the brush or a gloved finger, so it fills the line rather than sitting on the tile. Leave it for about ten minutes. You may see light fizzing; that is the peroxide working.

Step 4: Scrub

Scrub along the length of each grout line with the stiff brush, using short, firm strokes. A proper grout brush has bristles that fit the line and saves a lot of effort compared with a toothbrush. An old electric toothbrush is a good middle ground for small areas. Work in sections you can reach without stretching, and do not let the paste dry on, because dried baking soda is a pain to rinse.

Step 5: Rinse and dry

Wipe up the paste with a cloth wrung out in clean water, then mop or wipe the whole area with fresh water so no residue is left to attract dirt. Change the water when it goes cloudy. Dry the floor with a towel or let it air for an hour. Grout always looks darker when wet, so judge the result only when it is fully dry.

For mildew in showers

Black or pink spots in shower grout are mold and mildew, not dirt, and they need a different approach. Spray undiluted hydrogen peroxide on the lines, leave it for ten minutes, scrub with the brush and rinse. Repeat for stubborn spots. Peroxide kills the growth rather than bleaching it, and it will not damage grout the way vinegar does. Run the fan or open a window after showers so the grout can dry; mildew only grows where it stays wet.

For grout that is still dark

If the lines are still grey or brown after the paste, use oxygen bleach, sold as powder for laundry and cleaning. Mix it with warm water according to the packet, pour or sponge it onto the grout, leave it for fifteen to thirty minutes while keeping it wet, then scrub and rinse. Oxygen bleach is gentler than chlorine bleach, does not fume, and is safe on colored grout. Chlorine bleach is a last resort: it lightens grout unevenly and should never be mixed with anything else.

Grout that stays stained after oxygen bleach is usually stained all the way through. At that point the options are a grout colorant, which paints and seals the lines in one go, or regrouting.

Step 6: Seal the grout

This is the step that makes the difference next time. Once the grout is clean and completely dry, which means waiting a day, apply a penetrating grout sealer with a small brush or applicator bottle along every line, wipe any excess off the tile before it dries, and let it cure for the time on the label. Sealed grout sheds water and dirt, so a weekly mop keeps it looking clean. Reseal once a year, or when water stops beading on the grout.

Common mistakes

• Using vinegar or acidic tile cleaners on grout every week.
• Scrubbing with a wire brush, which scratches tile and gouges grout.
• Letting the paste dry on the floor.
• Judging the result while the grout is still wet.
• Cleaning the grout perfectly and never sealing it.

Keeping it clean

Sweep floors before you mop so grit does not get ground in. Mop with a neutral floor cleaner, not vinegar. Squeegee shower walls after use and keep the fan running until the tile is dry. Spot-treat any mildew the week it appears, when a quick spray of peroxide is all it takes.

FAQ

What is the best homemade grout cleaner?

A paste of baking soda and hydrogen peroxide, left on the grout for ten minutes and scrubbed with a stiff brush, handles most everyday dirt. For mildew in a shower, hydrogen peroxide on its own, sprayed and left to sit, works better than baking soda.

Can I use vinegar on grout?

Vinegar cleans grout but also slowly eats it, because grout is cement-based and the acid dissolves it. An occasional use on sealed grout is fine; regular use, or use on unsealed or natural stone tile, is not. Baking soda and peroxide do the job without the damage.

Why does my grout look dirty again a week after cleaning?

Unsealed grout is porous and soaks dirt and water straight back in. Seal it once it is clean and dry, and the dirt stays on the surface where a mop can lift it.

Should I use a steam cleaner on grout?

Steam works well on floor grout and needs no chemicals, but it also strips sealer, so plan to reseal afterward. Keep it off grout that is cracked or crumbling, because the heat and pressure can make it worse.