How to clean grout gaps

Restore stained grout to like-new condition

Why grout gets dirty

Grout is porous — even sealed grout absorbs some moisture, oils, and dirt over time. Bathroom grout discolours from soap scum, body oils, and mould. Kitchen grout stains from cooking oils and spills. Floor grout darkens from foot traffic grinding dirt into the surface. This is normal and doesn't mean the grout has failed — it just needs cleaning.

Start gentle, escalate if needed

Always start with the mildest cleaning method and only escalate if it doesn't work. Aggressive chemicals can damage tile glazes and dissolve grout if used incorrectly.

Level 1: Warm water and a stiff brush

For light discolouration, warm water and a nylon bristle brush is often enough. Scrub along the grout lines, rinse, and dry. An old toothbrush works well for small areas. This should be your routine monthly maintenance.

Level 2: Baking soda paste

Mix baking soda with water to form a thick paste. Apply to grout lines, let it sit for 15 minutes, then scrub with a brush. Baking soda is mildly abrasive and alkaline — effective against grease and light mould without damaging tiles or grout. Rinse thoroughly.

Level 3: Vinegar or hydrogen peroxide

For stubborn stains, spray white vinegar or 3% hydrogen peroxide onto the grout, wait 10 minutes, then scrub. Do not use vinegar on natural stone tiles — the acid etches marble, limestone, and travertine. Hydrogen peroxide is safer for stone but test in an inconspicuous area first.

Level 4: Commercial grout cleaner

Purpose-made grout cleaners contain stronger chemicals designed for tile surfaces. Follow the manufacturer's instructions exactly — leaving them on too long can damage grout. Ventilate the room well.

Level 5: Steam cleaning

A handheld steam cleaner directed at grout lines blasts away deep-set dirt and kills mould spores without any chemicals. Effective for bathroom grout that's been neglected. The heat also helps sterilise the surface.

Dealing with mould

Black mould in shower grout is the most common grout problem. After cleaning, the key is prevention: improve ventilation (run the extractor fan for 15 minutes after every shower), squeegee tile walls after use, and apply a mould-resistant grout sealer.

If mould has penetrated deep into the grout and returns within days of cleaning, the grout may need to be raked out and replaced. Use a grout rake to remove the old grout to half the tile depth, then regrout with a mould-resistant formula.

Sealing grout

After cleaning, apply a penetrating grout sealer to protect against future staining. Sealer fills the microscopic pores in cement grout, making it water- and stain-resistant. Re-apply every 1-2 years in wet areas, every 3-5 years for dry floors.