Grout is porous, sits slightly recessed between tiles, and collects everything that lands on it. In kitchens, that means grease and food residue. In bathrooms, it means soap scum, mineral deposits, and eventually mould. The good news is that most grout can be restored with the right approach and without stripping out your weekend.
Why Grout Gets Dirty Faster Than Tiles
Ceramic, porcelain, and stone tiles have a sealed, non-porous surface. Grout is usually a cement-based material that is genuinely porous unless it has been sealed. Liquids, oils, and particles are absorbed rather than sitting on the surface.
This means surface wiping has limited effect on grout. You need either a chemical that penetrates and lifts the residue, or physical scrubbing that gets into the texture of the grout, or both.
What You Will Need
The tools matter more than most people expect. A standard kitchen sponge is too soft to clean grout effectively. You need:
- A stiff-bristled grout brush (narrow enough to stay in the grout line)
- An old toothbrush for tighter spots
- Your chosen cleaning solution
- A bucket of clean water and a cloth for rinsing
Cleaning Methods Ranked by Strength
1. Bicarbonate of Soda and Warm Water (Light Staining)
Make a paste from bicarbonate of soda and a small amount of warm water. Apply to grout lines with a brush, leave for a few minutes, scrub, and rinse. This is gentle enough for regular maintenance and safe on all tile types including natural stone.
Good for: light surface discolouration, regular upkeep between deeper cleans.
2. White Vinegar Spray (Mineral Deposits and Soap Scum)
Undiluted white vinegar cuts through calcium deposits and soap scum. Spray directly onto the grout, leave for five minutes, scrub, and rinse.
Do not use vinegar on natural stone tiles. The acid in vinegar etches marble, travertine, slate, and similar surfaces. Use a pH-neutral stone cleaner instead.
Good for: bathroom grout with hard water staining, shower enclosures in areas with hard water.
3. Bicarbonate of Soda and Vinegar (Moderate Staining)
Apply the bicarb paste first, then spray with vinegar. The fizzing reaction helps lift residue from the grout texture. Scrub and rinse once the fizzing settles.
Good for: moderately stained bathroom or laundry grout where the above methods alone are not quite enough.
4. Oxygen Bleach (Stubborn Staining and Light Mould)
Oxygen bleach products (sodium percarbonate, sold as a powder) are effective on organic staining and light mould without the harshness of chlorine bleach. Mix to a solution following the product instructions, apply to grout, leave for 15 to 30 minutes, scrub, and rinse.
Good for: kitchen backsplash grout with accumulated grime, bathroom grout with early mould growth.
5. Chlorine Bleach Solution (Mould)
A diluted bleach solution (one part bleach to four parts water) is the most effective treatment for mould in grout. Apply, leave for 10 to 15 minutes, scrub, and rinse thoroughly.
Good for: established mould growth in bathroom grout.
Not suitable for: coloured grout (can fade), natural stone, or anywhere the runoff cannot be controlled.
Grout That Will Not Come Clean
If grout remains heavily discoloured after a thorough treatment, there are two practical options.
Grout pen or colourant. These are applied over existing grout to restore or change the colour. They are a cosmetic fix, not a deep clean, but they work well when the grout is structurally sound and the staining is purely surface-level.
Re-grouting. Removing and replacing old grout is more involved but sometimes the right answer, particularly in showers where grout has cracked or where mould has penetrated so deeply that surface treatment keeps failing.
Sealing Grout After Cleaning
Once the grout is clean and fully dry, applying a grout sealer significantly reduces how quickly it gets dirty again. Sealers create a surface barrier that makes the grout less porous, so spills sit on the surface rather than being absorbed.
Most grout sealers are applied by brush or pen directly to the grout line, left to cure, then buffed. Re-sealing every one to two years is a reasonable maintenance interval for bathroom and kitchen areas.
Keeping Grout Cleaner Between Deep Cleans
The single most effective habit for bathroom grout is running a quick spray of diluted cleaner and a brief scrub once a week rather than leaving it to accumulate. It takes a few minutes and prevents the build-up that requires an hour to address later.
For kitchen splashback grout, wiping it down with a damp cloth after cooking while the grease is still fresh is far easier than treating it once it has dried and set.
Tip: If your bathroom grout keeps developing mould despite regular cleaning, check the ventilation. Mould returns because of moisture, not because the cleaning was inadequate. Running your exhaust fan for 10 to 15 minutes after every shower makes a noticeable difference over time.