Why Grout Gets Dirty So Quickly

Grout is a porous material — it readily absorbs moisture, soap scum, mould spores, grease, and general grime. In kitchens, splashbacks are constantly hit with cooking residues. In bathrooms, steam and soap build-up create ideal conditions for mould and mildew. Without regular attention, grout lines darken, stain, and become increasingly difficult to restore.

The good news is that with the right approach, most grout can be brought back to looking near-new without expensive products or professional help.

What You'll Need

  • A stiff-bristled grout brush or old toothbrush
  • Bicarbonate of soda (baking soda)
  • White vinegar or hydrogen peroxide
  • Washing-up liquid
  • Spray bottle
  • Old towels or rags
  • Rubber gloves
  • Optional: commercial grout cleaner for stubborn cases

Method 1: Regular Maintenance Clean

For grout that's only mildly dirty, a simple routine clean is usually sufficient.

  1. Mix a few drops of washing-up liquid with warm water in a spray bottle.
  2. Spray along grout lines and leave for 2–3 minutes.
  3. Scrub with a grout brush using firm, circular motions.
  4. Rinse thoroughly with clean water and dry with a cloth.

Do this weekly or fortnightly in shower areas and kitchens to prevent build-up from becoming entrenched.

Method 2: Bicarbonate of Soda Paste (Moderate Staining)

For grout that's noticeably discoloured but not heavily mouldy, a bicarbonate of soda paste is highly effective and completely safe for tiles and grout.

  1. Mix bicarbonate of soda with a small amount of water to form a thick paste.
  2. Apply the paste directly to grout lines with an old toothbrush or your finger.
  3. Spray white vinegar over the paste — it will fizz. This reaction helps lift dirt and kill mild mould.
  4. Leave for 5–10 minutes, then scrub and rinse.

Note: Avoid using vinegar on natural stone tiles (marble, limestone, travertine) as the acid can etch the surface. Use plain water with bicarbonate of soda instead.

Method 3: Hydrogen Peroxide for Mould and Mildew

For grout with visible mould — common in shower cubicles and around baths — hydrogen peroxide (3% solution, available from pharmacies) is an effective treatment.

  1. Apply 3% hydrogen peroxide directly to affected grout lines using a spray bottle or cotton wool.
  2. Leave for 10–15 minutes. Don't rinse immediately.
  3. Scrub with a grout brush, then rinse with warm water.
  4. Repeat for stubborn patches.

Method 4: Commercial Grout Cleaners (Heavy Staining)

For grout that has years of build-up or heavy mould staining, a purpose-made grout cleaner or a bleach-based solution may be necessary. Always follow the manufacturer's instructions and ensure the room is well-ventilated. Test in an inconspicuous area first, particularly on coloured grout.

How to Keep Grout Clean for Longer

  • Seal your grout — applying a grout sealer once or twice a year creates a protective barrier that significantly reduces staining and moisture absorption.
  • Dry your shower after use — a quick wipe-down with a squeegee or towel after showering dramatically slows mould growth.
  • Ventilate bathrooms properly — use extractor fans and open windows to reduce humidity.
  • Clean little and often — a quick spray and scrub every week prevents the deep staining that requires hours of work to reverse.

When to Re-Grout Instead

If grout is crumbling, cracked, or the staining is so deep it can't be shifted despite thorough cleaning, re-grouting may be the better option. This is a manageable DIY task — raking out old grout and applying fresh grout is straightforward with basic tools and a little patience. Fresh grout sealed immediately will stay cleaner for far longer than old, unsealed grout.