How to Deep Clean Bathroom Grout

Grout collects dirt, mold, and soap scum faster than almost anything else in your bathroom. It's porous—essentially tiny concrete channels between your tiles—so it traps moisture and grime that surface cleaning never touches. Deep cleaning grout isn't complicated, but it requires the right tools, some patience, and the willingness to scrub. Done well, you'll see grout go from gray and dingy back to its original color, and you'll restore the visual freshness of an entire shower or floor in a single afternoon. The key is understanding that surface sprays won't cut it. You need penetration: something that breaks down the buildup chemically, sits for a moment to work, then gets agitated away with a brush. This guide walks you through the methods that actually work, from gentle baking soda approaches for light jobs to stronger interventions for mold and years of accumulation.

1. Clear and ventilate the bathroom. Remove any items from shelves, the tub edge, or floor around the work area. Open windows and turn on the exhaust fan to run for the entire project. If using any chemical cleaners, crack a door open for continuous airflow.
2. Dry the grout completely. Use a towel or mop to remove standing water from floors, or wipe down shower walls. Let the space air-dry for at least 30 minutes before starting. Wet grout won't accept cleaner as effectively, and moisture can dilute your working solution.
3. Apply your chosen cleaner. For light jobs, mix baking soda and hydrogen peroxide into a thick paste (roughly 3 parts baking soda to 1 part peroxide). For heavier buildup or mold, use a commercial grout cleaner per label instructions, or dilute household bleach at a 1:10 ratio with water. Apply the paste or liquid generously along all grout lines using an old toothbrush or small applicator bottle.
4. Let the cleaner sit and penetrate. Set a timer for 10–15 minutes. The baking soda mixture needs time to break down the organic matter; bleach-based cleaners need similar dwell time to kill mold and lighten stains. Resist the urge to scrub immediately—the chemistry does the heavy lifting if you're patient.
5. Scrub with a stiff brush. Use a grout brush, old toothbrush, or small handheld wire brush to agitate the grout lines in a circular or back-and-forth motion. Apply firm pressure but don't gouge. For floor grout, you can also use a floor scrubber with a stiff nylon head. Work methodically through the entire grouted area.
6. Rinse thoroughly with clean water. Use a spray bottle or handheld shower head to rinse all grout lines and tiles. You're removing both the dissolved grime and any cleaner residue. For floors, use a mop with clean water; for shower grout, spray from top to bottom and let water run down the walls. Do this twice—the second rinse ensures no cleaner remains.
7. Dry and inspect. Towel off the area or let it air-dry completely. Once dry, you'll see the true color and cleanliness of your grout. If stains or mold persist in certain spots, spot-treat those areas and repeat steps 3–6 for just those sections.
8. Apply grout sealer (optional but recommended). Once the grout is fully dry (wait at least 24 hours), apply a penetrating grout sealer with a small brush or applicator bottle. Follow the product instructions for drying time. Sealer won't prevent future cleaning, but it makes grout resist stains and mold for 2–3 years, cutting down on how often you need to deep clean.