How to Clean Grout

Most grout is cement-based and slightly porous. In kitchens it absorbs grease and food; on floors it soaks up dirty mop water; in bathrooms it picks up soap scum and mould. Light-coloured grout shows everything, which is why white grout lines often look grey within a year or two.

For regular dirt, warm water with a little washing-up liquid and a stiff (but not wire) brush is often enough. Grout brushes are narrow and help, but an old toothbrush works for small areas. Scrub along the grout line, rinse with clean water and dry with a towel.

For tougher dirt, a paste of bicarbonate of soda and water left for 10–15 minutes before scrubbing gives a little more cleaning power without being harsh.

Oxygen-based cleaners (often sold as 'oxygen bleach' powders) are a good next step for discoloured grout, and are generally gentler on coloured grout than chlorine bleach. Mix and apply them according to the instructions, leave for the recommended time, scrub and rinse.

Dedicated grout cleaners are also available. Whatever you use, test a small hidden area first, especially on coloured grout, and wear gloves.

Black spots in shower grout are usually mould. A mould remover and a brush will lift surface growth; ventilation and wiping down after showers stops it coming back. If the mould has penetrated deeply or the grout is crumbling, it may need raking out and regrouting. See how to get rid of mould in the bathroom.

Floor grout gets dirty from mopping as much as walking – dirty mop water settles in the lines. Change the water often, use the right amount of floor cleaner (too much leaves a sticky residue that attracts dirt) and rinse. A steam cleaner can help on tiled floors, but check that your tiles and grout are suitable first.

Once grout is clean and completely dry, a grout sealer helps it resist stains and water. It's a quick job with a small brush or applicator pen, and worth doing on kitchen splashbacks, floors and showers. Grout pens can also refresh the colour of lines that won't come clean, although they cover rather than clean.

Coloured grout can fade or blotch if cleaned with bleach or strong oxygen cleaners, so stick to warm soapy water, a soft brush and products specifically labelled as safe for coloured grout. Test first in a corner.

Epoxy grout, often used in showers and kitchens because it's more water- and stain-resistant, doesn't absorb dirt in the same way as cement grout. It usually only needs regular cleaning with a mild detergent. Harsh chemicals can dull its surface.

Scrubbing grout by hand is slow. An average bathroom floor can take an hour or more; a fully tiled shower even longer. Working in small sections, letting the product do the work and using a proper grout brush rather than a toothbrush makes it far more manageable.

Electric rotary scrubbers with small brush heads can speed things up considerably on larger areas. Steam cleaners can also help on tiled floors and sealed grout, but check your tiles and grout are suitable before using one.

If grout is cracked, crumbling or missing, cleaning won't fix it, and water can get behind the tiles. That's a job for a tiler. If it's simply very dirty across a whole bathroom or kitchen, a professional deep clean can save you hours of scrubbing on your knees.