How to Clean Grout Without Damaging Tiles
Published 18 June 2026 · Bridgnorth Bathroom Fitters
Grout discolours faster than the tile around it. Cement-based grout is porous, absorbs dirt and soap residue, and is prone to mould. Cleaning it properly restores a tired bathroom almost as effectively as new tiles — but using the wrong product can damage the tile itself, which is the worst possible outcome.
This guide covers what works on each tile type, and what to avoid.
Why grout discolours
Several factors:
- Soap and skin oils absorb into the porous grout surface
- Mould grows in damp grout, particularly in shower areas
- Limescale builds up on grout where water repeatedly evaporates
- Wear and abrasion from cleaning gradually thins the grout surface, exposing more porosity
White grout shows discoloration most prominently. Grey or coloured grout hides it better but still discolours.
Step 1: Identify your tile
Different tiles tolerate different cleaning products. The wrong product can permanently etch the tile surface.
Porcelain
Hard, dense, non-porous (mostly). Tolerant of most cleaners including mild bleach and proprietary grout cleaners. Most forgiving.
Glazed ceramic
The glaze is non-porous. Tolerant of most cleaners. Avoid abrasive scrubbing on glossy surfaces — fine scratches show.
Natural stone — marble, limestone, travertine
Acid-sensitive. Anything acidic (vinegar, lemon juice, descalers, some “grout cleaners” that are acid-based) will etch the surface. Even mild acid leaves dull patches.
Use pH-neutral cleaners only. Specialty stone-safe cleaners exist.
Natural stone — slate, granite
Less acid-sensitive but still treat with care. Test in an inconspicuous corner first.
Cement-effect porcelain
Treat as porcelain.
Wood-effect porcelain
Treat as porcelain.
Glass tile or mosaic
Most cleaners fine. The grout between is usually the issue, not the tile.
If you don’t know your tile type, test any new cleaner on a hidden area (behind the WC, in a corner of the cupboard) before using widely.
Step 2: Routine grout cleaning
For grout that’s slightly grubby but not heavily discoloured:
Method 1: Soap-and-water scrub
- Hot water with mild detergent (washing-up liquid is fine)
- Stiff brush (old toothbrush for detail, larger brush for area)
- Scrub the grout lines firmly
- Rinse with clean water
- Dry with a cloth
This handles surface dirt and prevents buildup. Doesn’t remove deep stains or mould.
Method 2: Baking soda paste
- Mix baking soda with water to a paste consistency
- Apply to grout lines
- Leave 10–15 minutes
- Scrub with brush
- Rinse thoroughly
Mildly abrasive, mildly alkaline. Effective on light staining. Safe on most tile types including (gently) on natural stone.
Step 3: Mould in grout
Black mould (technically usually a mildew or surface fungal growth) requires different treatment.
Method 1: Diluted bleach (porcelain and ceramic only)
- 1 part household bleach to 4 parts water
- Apply with a brush to mouldy grout
- Leave 10–15 minutes (don’t let dry)
- Scrub
- Rinse thoroughly
- Ventilate well during and after
Do not use on natural stone, brass surfaces, or coloured grout (bleach lightens coloured grout).
Method 2: Hydrogen peroxide
- 3% hydrogen peroxide (standard pharmacy strength)
- Spray on mouldy areas
- Leave 5–10 minutes
- Scrub
- Rinse
Gentler than bleach, still effective. Safer on more surfaces.
Method 3: Proprietary mould cleaners
- HG, Astonish, Cif, others
- Follow product instructions
- Most contain bleach as active ingredient
- Some are stone-safe — check the label
Method 4: White vinegar (porcelain and ceramic only)
- Apply neat
- Leave 30 minutes
- Scrub
- Rinse
Mildly acidic — never use on natural stone, marble especially. Effective on surface mould and limescale.
Step 4: Heavy grout stains
For grout that’s deeply discoloured, no surface cleaning will fully restore it. Options:
Method 1: Grout reviver
A specialty paint that coats over existing grout. Restores colour, can be applied in colours other than original.
- Brush on
- Wipe off excess from tile surfaces immediately
- Dries in a few hours
- Lasts 2–3 years before needing reapplication
Effective for visual restoration but doesn’t fix structural issues with the grout itself.
Method 2: Replace grout entirely
Rake out the old grout with a grout rake or oscillating multitool, vacuum the channels, apply new grout, sponge off the excess, polish when dry.
More effort but a proper restoration that lasts years. Best done in larger areas (whole shower wall) rather than spot patches.
Method 3: Professional cleaning
Some companies offer steam cleaning or specialty chemical treatment that restores grout colour without replacement. Costs less than re-grouting; effective on many situations.
Specific scenarios
Black mould in shower silicone vs shower grout
If the mould is in the silicone joints (where tile meets bath, in corners), it’s almost always inside the silicone — needs sealant removal and replacement. See how to re-seal a shower.
If it’s in the grout between tiles, surface cleaning often works. If it’s deep, re-grouting may be needed.
Limescale on grout
Common in hard water areas. Diluted vinegar (porcelain only), proprietary limescale removers (check tile compatibility), or repeated mild scrubbing usually restores.
Soap scum on grout
The buildup of soap, body oils and hard water residue. Alkaline cleaners (baking soda, mild ammonia products) cut through this effectively.
Discoloration concentrated at floor edges
Often from cleaning chemicals from the floor splashing onto grout. Switch cleaning products or pre-rinse the floor before cleaning.
What NOT to do
- Steel wool or abrasive scrubbers — scratch tile permanently, particularly polished surfaces
- Mixing bleach with vinegar or ammonia — produces toxic chlorine gas
- High-pressure power washers — can erode grout and dislodge sealant
- Acid-based cleaners on natural stone — etches the surface permanently
- Repeated use of very strong cleaners — degrades grout over time, makes it more porous and more prone to future staining
Prevention is easier than cure
The best grout cleaning routine prevents staining rather than fixing it:
- Squeegee shower walls after each use (yes, this again — it’s the most important single thing)
- Ventilate the bathroom properly — extractor running 15–30 minutes after showers
- Wipe wet surfaces to dry where possible
- Avoid heavy chemicals for daily cleaning — they accelerate grout degradation
- Anti-mould treatment every 3 months as preventative
A new grout treated this way stays looking new for 5+ years. A neglected grout looks tired within 12 months.
Grout sealer
Applying a grout sealer after installation (or after deep cleaning) makes grout more resistant to staining. Penetrating sealers soak into the grout and form a hydrophobic barrier without changing the appearance significantly.
For new bathrooms, we typically seal grout as part of handover. For existing bathrooms, you can apply yourself:
- Clean grout thoroughly first
- Let dry completely
- Apply sealer with a small brush along grout lines
- Wipe off any excess from tile surfaces
- Allow to dry per product instructions
Re-apply every 1–2 years.
When to consider re-grouting
If cleaning doesn’t restore the look and grout reviver isn’t appropriate, full re-grouting is the answer. Signs you should re-grout rather than just clean:
- Cracking in multiple grout lines
- Missing sections of grout
- Grout pulling away from tile edges
- Deep staining that resists multiple cleaning attempts
- Smell of damp or visible damp behind tile (urgent — investigate cause)
Re-grouting costs £15–£25/m² as a standalone job. Often done as part of a wider refurbishment.
FAQ
Will bleach lighten my coloured grout? Yes — both immediately and over time with repeated use. Use a colour-safe cleaner instead.
My grout has gone yellow — what causes that? Usually soap residue and oils oxidising into the grout. Baking soda paste is often the most effective home remedy.
Should I use a grout brush or a toothbrush? A grout brush has stiffer bristles and covers area faster. Old toothbrushes work for detail and corners.
How long should grout last? 20+ years if properly installed and maintained. Some grout needs re-doing in 10–15 years in heavily-used bathrooms.
Need help with grout that’s beyond cleaning?
If your grout is beyond restoration with surface cleaning, get in touch. We re-grout bathrooms regularly and can usually return a tired-looking room to fresh-looking very efficiently.