How to Clean Grout Between Tiles: Safe, Step-by-Step Methods

Start by removing loose debris, test any cleaner on an out-of-sight area, apply a tile-safe cleaner, scrub the grout lines with an appropriate brush, then rinse and dry thoroughly. For stubborn stains or mildew consider targeted spot treatments, steam cleaning, or regrouting, and protect the cleaned grout with a sealer to reduce future staining.

Why grout gets dirty and what that means for cleaning

Grout is porous and sits lower than tile surfaces, so it collects dirt, oils, and moisture more readily. Organic growth such as mildew and mold often appears in damp areas and typically needs different treatment than surface dirt. Understanding whether a stain is surface soil, a deep-set discoloration, or biological growth helps choose the safest effective method.

Safety, testing, and cleaner selection

Always protect yourself and your surfaces. Work with good ventilation, wear gloves and eye protection for concentrated products, and never mix household chemicals. Test cleaners on an inconspicuous tile and grout patch and wait for full drying to confirm there is no damage or discoloration.

To pick a cleaning product, consult a Tile-safe cleaner selection guide that distinguishes neutral-pH cleaners suitable for glazed tile from products that are unsafe for natural stone. Avoid acidic cleaners like straight vinegar on slate, marble, or limestone because they can etch these stones.

Tools and supplies you will need

Soft bristled grout brush or nylon brush (avoid wire brushes on softer tile).
Microfiber cloths or mop for rinsing.
Bucket, spray bottle, and gloves.
Tile-safe cleaner, oxygen-based bleach (for organic stains) or a commercial grout cleaner as appropriate.
Optional: steam cleaner and grout sealer.

For recommendations on brushes and specialty tools, see our Best brushes and tools for tile grout cleaning resource.

Step-by-step cleaning method

Dry clean first. Sweep or vacuum to remove loose dirt and dust from tile and grout so you are not pushing grit into the lines during scrubbing.
Test your cleaner. Apply a small amount of your chosen cleaner to an inconspicuous area and wait for it to dry. If the tile or grout color changes, do not use that product.
Apply cleaner to grout. For general cleaning, a paste of baking soda and water applied to grout can help lift soils; for mildew or organic stains use an oxygen-based cleaner following manufacturer directions. For commercial products, follow dilution instructions.
Allow dwell time. Let the cleaner work for the time recommended on the product label or 5 to 10 minutes for homemade pastes. Do not let strong chemicals sit long enough to dry on the tile surface.
Scrub with a grout brush. Use firm, even strokes along the grout line. Avoid metal brushes on delicate tile. For very narrow lines, a toothbrush or a narrow grout brush can reach better.
Rinse thoroughly. Remove all cleaner residues with clean water. Use a microfiber cloth or mop to avoid redepositing dirt.
Dry and inspect. Use towels to dry the grout. Inspect for remaining stains and repeat spot treatments if needed.

Options for persistent stains and mildew

When the basic method does not clear a stain, choose the approach suited to the cause:

Deep organic stains or mildew: Oxygen-based bleach solutions are effective against biological growth without the strong fumes of chlorine bleach. Always follow label directions and rinse well.
Mold in grout joints: For small affected areas, a targeted application with a grout brush and an appropriate cleaner is safer than flooding the area with strong chemicals.
Old, discolored grout: If cleaning does not restore the grout, regrouting the lines or color-matching with grout stain may be necessary.
Steam cleaning: Steam can loosen soils and kill organic growth without chemicals; it may not remove deep mineral staining.

Comparison at a glance:

Oxygen-based cleaners: milder, good for organic stains, safe on most tiles.
Chlorine bleach: powerful against mildew, strong fumes, can discolor colored grout and damage some surfaces.
Steam: chemical-free option, effective for surface soils and mildew, less effective on mineral stains.
Regrouting: most permanent for structural or color problems but is labor intensive.

When to seal grout and basic sealing guidance

Sealing is a preventive step that reduces how quickly grout re-stains. Sealers vary by type; manufacturers recommend applying a sealer when grout is thoroughly clean and fully cured per the grout product instructions. If you are unsure whether to seal, consult guidance such as How to seal grout for long-term protection and follow the sealer maker's directions for application frequency.

General preparation steps before sealing: clean and dry grout completely, remove any old sealer if it is failing, and apply a sealer evenly with a small applicator or brush. Wipe excess sealer from tile surfaces promptly.

Common mistakes and a quick checklist

Avoid these frequent errors that make grout cleaning less effective or damage surfaces.

Using acidic cleaners on natural stone — can etch and dull the tile surface.
Not testing products in an inconspicuous area before treating the whole floor.
Mixing cleaners such as bleach and ammonia — hazardous gas can form.
Scrubbing with metal brushes on softer tiles — causes scratches.
Skipping rinsing — residues attract soil and make grout dirty faster.

Quick pre-clean checklist:

Ventilate the room and put on gloves.
Vacuum or sweep away loose debris.
Test cleaner on a hidden spot.
Use appropriate brush and follow dwell times.
Rinse, dry, and decide if sealing is needed.

Worked example: removing mildew from a shower floor

Situation: darkened grout in an otherwise clean shower floor.

Sweep and rinse the shower to remove soap scum.
Test an oxygen-based grout cleaner on a corner tile and wait for results.
Apply cleaner along the grout lines, let it sit per label instructions, then scrub with a nylon grout brush.
Rinse well and dry. If darkening persists, repeat or consider steam cleaning.
Once clean and dry, apply a sealer suitable for shower environments following the product instructions.

Closing: what to expect and maintenance tips

Regular light cleaning prevents heavy build up and reduces the need for aggressive treatments. Keep a small grout brush and a neutral cleaner on hand for monthly maintenance in high traffic or moist areas. If repeated cleaning fails to restore grout appearance, consider regrouting or professional assessment.

For more on choosing cleaners, tools, and when to seal, review our internal guides: Tile-safe cleaner selection guide, Best brushes and tools for tile grout cleaning, and How to seal grout for long-term protection.