How to Clean Grout: Methods Compared, Stains & Mould

Grout is the cheapest part of a tiled wall or floor and the part that shows every mistake. It is porous, so it soaks up soap, grease and moisture. It is alkaline, so strong acids can eat into it. It is often tinted, so bleach can lighten it unevenly. And it sits in lines only a few millimetres wide, so a wrong product or a hard-bristled brush can wear it away. The right cleaner depends on what is staining it, what colour it is and what your tiles are made of.

This guide opens with a side-by-side table of the main methods, then covers how to check your grout and set up safely, goes through each option in turn, deals with specific problems and rooms, and ends with sealing, prevention and the signs that cleaning is not enough. If you only read one part, read the table and the verdict near the end.

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Grout cleaning methods compared

The short version: start with washing-up liquid and a brush, move to oxygen bleach for stains, use diluted chlorine bleach only on white grout with mould, treat acids with caution on cement, and use a pen for cosmetic touch-ups. If the grout is crumbling, cleaning cannot fix it.

Know your grout, then set up properly

What kind of grout is it?

Most UK homes have cement-based grout, which is porous, sometimes tinted and usually needs sealing. Epoxy grout, found in some showers and kitchens, is a resin, so it is far less porous and stain resistant, but it can still be scratched, and you should follow the maker’s cleaning advice. You can usually tell by age and location: grout in older bathrooms, floors and kitchens is almost always cement. If you do not know, assume cement and use the gentler options.

The water test

Put a few drops of water on a clean, dry bit of grout. If it beads, the grout is sealed or non-porous. If it darkens and sinks in within a minute or so, it is unsealed or the sealer has worn, and it will stain faster and take cleaners deeper. That is useful to know, because unsealed grout often needs resealing after cleaning, and it explains why some lines come up darker again within weeks.

Check the tiles too

Natural stone such as marble, limestone, travertine and some slate reacts with acids, which etch the polished surface, and strongly alkaline cleaners can dull it. For stone, use a neutral stone-safe cleaner and keep vinegar, lemon and limescale removers away. Glazed ceramic and porcelain tolerate most things, but the metal fittings next to the grout may not. Test whatever you use in a hidden corner first.

Prep and safety that apply to every method

• Open a window and run the extractor fan. Fumes build up quickly in small bathrooms.
• Wear rubber or nitrile gloves, and eye protection if you are spraying or scrubbing overhead.
• Never mix cleaning products. Bleach with vinegar, other acids or ammonia releases harmful gases. Our list of cleaning products you should never mix covers the combinations to avoid.
• Sweep or vacuum first, so you do not grind grit into the lines, and brush dry loose debris from the grout.
• Mask off nearby surfaces such as painted walls, metal fittings and wood if you are using anything stronger than detergent.
• Work in sections of about a square metre, so nothing dries on the surface before you reach it.
• Wear non-slip shoes and use knee pads if you are working on a floor.

The brush matters

A stiff nylon grout brush with an angled head gets into the line without scratching tiles. A grout brush with stiff nylon bristles is worth having for floors and wall grout, and an old toothbrush does the corners. Look for a brush that is stiff but not metal, a head narrow enough to sit in the joint, and a comfortable handle. Steel wool and wire brushes scratch the tile glaze and gouge the grout, which then holds dirt more easily. Electric scrubbers with a soft brush head are a reasonable choice for large floors, and our guide to cleaning quarry tiles uses the same approach on a larger scale.

Option by option

Hot water, washing-up liquid and a brush

This is the sensible first move for kitchens and floors, and it fixes more than people expect. Mix a squirt of washing-up liquid into hot water, apply it with a sponge or brush, scrub along the line, and rinse. In kitchens, grease is the main problem, and washing-up liquid is designed to cut it. Leave the mix on greasy grout for 10 to 15 minutes before scrubbing. Rinse with clean water and dry with a cloth, because leftover soap attracts dirt. For a bathroom, plain detergent will not shift mineral scale, but it clears the soap and body oil that sits on top and helps other cleaners reach the stain.

Bicarbonate of soda paste

Mix bicarbonate of soda with a little water into a thick, spreadable paste, press it into the grout with a brush, leave it 15 to 20 minutes, scrub with a toothbrush and rinse thoroughly. It is a mild alkali and a gentle abrasive, so it lifts light staining and absorbs odours, and it suits cement grout in light colours. Rinse well, because dried residue leaves a white film on tiles. It is not strong enough for deep stains or black mould roots. Do not combine it with vinegar on the grout and expect extra power: the fizz is mostly show, because the two neutralise each other, as our page on whether baking soda and vinegar clean explains. For a stubborn patch, mix the powder with washing-up liquid instead, cover it with cling film to keep it damp, and leave it for a few hours before scrubbing.

Oxygen bleach: the colour-safe all-rounder

Oxygen bleach cleaners are based on sodium percarbonate, which releases oxygen in water and lifts stains from within porous grout. They are usually safe for coloured grout, have little smell and are gentler on you and the room than chlorine bleach. Follow the pack: most are powders dissolved in warm water. Apply the solution to the grout, keep it wet for the recommended time, which is often 15 to 20 minutes or longer, scrub and rinse. Warm water usually helps. A ready-made oxygen bleach grout cleaner is the first thing to try on stained grout. Look for a product that says it is for grout or tile, check whether it is safe for coloured grout and your tile type, and follow the contact time. Oxygen bleach is not a disinfectant in the way chlorine bleach is, and it works better than the label sometimes suggests on deep dark staining only after repeated treatments.

Hydrogen peroxide

Three percent hydrogen peroxide from a pharmacy is a mild oxidiser that lightens organic stains and mildew. Apply it with a cotton bud or spray bottle, cover with cling film to stop it drying, leave it for 30 minutes to a few hours, then scrub and rinse. It can lighten coloured grout, so test first. Do not mix it with vinegar, which can produce corrosive peracetic acid, and keep it in its dark bottle away from heat. Eye protection is worth wearing.

Chlorine bleach, for white grout and mould only

Household bleach (sodium hypochlorite) whitens and disinfects, so it is useful for mould-stained white grout. It strips colour from tinted grout, can weaken sealer and grout over repeated use, and gives off fumes that irritate the eyes and lungs. If you use it, dilute it according to the label, apply with a cloth or brush to the grout, keep the room ventilated, leave it for the time stated and rinse thoroughly. Never mix it with vinegar, limescale remover, oxygen bleach or ammonia-based products, and rinse any acid cleaner away fully before using bleach. Our pages on what kills mould and cleaning shower mould cover the choices in more depth.

Vinegar, citric acid and limescale removers

Acids dissolve limescale and soap scum, but cement grout is made of lime and cement, and acid dissolves that too. A short application of dilute vinegar or citric acid, followed by thorough rinsing, will not usually harm sound, sealed grout, but repeated or long contact eats away at the surface, makes it rougher and increases staining. Use acid only for mineral scale, keep contact short, rinse well with clean water, and keep it off natural stone, unsealed grout and metal fixtures. Strong acid grout cleaners, such as hydrochloric or phosphoric acid products, are the riskiest of all. Only use one if the label says it is for your grout and tile type, and follow it to the letter. Avoid hot vinegar sprays heated in a microwave, as fumes are unpleasant in a small room.

Steam

A steam cleaner with a small brush or nozzle uses heat and moisture to loosen grime and kills many germs without chemicals. It works best on sound, sealed cement grout and on epoxy, and it is useful for people who would prefer to avoid chemicals. Move the nozzle slowly along the line, wipe up the loosened dirt with a microfibre cloth straight away, and keep the nozzle moving, as steam can lift loose tiles, damage cracked grout and drive moisture into the wall behind. Wear gloves, and keep children and pets away. It does not remove deep stains, so it is often followed by oxygen bleach. Check the tile maker’s guidance for hot steam on stone and some floor finishes.

Grout pens and paint

A grout pen or whitener paints a fresh colour onto clean grout, which is a good finish for tired lines when stains will not lift. It covers rather than cleans, so clean first and let the grout dry fully. Look for one that suits your location, because some pens are designed for walls and others cope with floors, and choose a shade that matches your existing grout. A white grout pen is the most common choice. Apply with a steady hand, wipe tile edges quickly and allow it to dry. Expect to touch up wear on floors over time.

The full process, start to finish

Whatever product you choose, the sequence is the same, and following it matters more than the brand.

1. Dry brush and wipe. Brush along each line with a dry brush to lift dust, hair and loose grit, then wipe or vacuum. This stops you turning dirt into a paste that sinks deeper into the pores.
2. Wet the grout lightly. A light spray of clean water stops very dry grout drinking up the cleaner too quickly. Do not soak it, particularly on walls.
3. Apply the cleaner. Use a spray bottle, brush or cotton bud for narrow lines, and work in sections of about a square metre. Cover the line fully, but avoid splashing the tile faces with anything stronger than detergent.
4. Let it dwell. Leave it for the time on the pack, topping up if the surface starts to dry. Dwell time does a lot of the work for you, so it saves scrubbing.
5. Scrub along the line. Use a stiff nylon brush with firm, steady strokes, following the length of the joint instead of across it. Use light pressure on epoxy and on tinted cement grout, and test first.
6. Rinse well. Use clean water and a cloth or sponge, working from the top down on walls. Change the water often. Leftover cleaner leaves a film that catches dirt and can damage grout over time.
7. Dry and look again. Wipe with a microfibre cloth and check in good light, using a torch held at a low angle to show missed spots. Wet grout always looks darker than dry grout, so judge the result once it is dry.
8. Repeat gently, or stop. One more careful round is better than one very hard one. If it has not improved after two or three attempts with the right product, move on to a pen or a repair.

Specifics for epoxy and tinted grout

Epoxy grout is much less porous, so dirt sits on the surface and usually comes off with a soft brush and a neutral cleaner. Its resin surface can be scratched, and some strong solvents and chlorine products may dull or discolour it over time, so follow the installer’s or maker’s cleaning advice and avoid abrasive pastes. Tinted cement grout can fade if you use chlorine bleach or strong acids, so lean on oxygen bleach and detergent, and avoid scrubbing hard on one spot. If the colour has already patchily faded, a grout pen or a colour sealer applied evenly can even it out.

Stubborn problems, one at a time

Black mould

Black or dark green patches in shower corners and along the sealant are usually mould, and it keeps coming back if the room stays damp. Wear gloves and ventilate. For light staining, oxygen bleach or a mould remover made for bathrooms works, and chlorine bleach used as above works on white grout. Scrub with a toothbrush, rinse, then dry the area thoroughly. If it returns within days, the cause is moisture. Look for a leak, poor ventilation or failed sealant, and read our guide to cleaning mould off walls. Large areas, mould that keeps spreading or anyone with asthma or breathing problems in the home are good reasons to get advice, and to fix the damp instead of repeatedly cleaning it.

Soap scum and limescale

Grey or white crust in showers and around taps is soap scum bound with hard water minerals. Begin with warm water, washing-up liquid and a brush to remove the soap. For remaining mineral scale, use a brief acid treatment as above, on suitable surfaces only, and rinse. A plastic brush will not scratch. Then dry the area. Our guide to cleaning shower tiles covers the surrounding surfaces.

Grease and food stains

Cooking splashes darken kitchen grout behind the hob. Use hot water and washing-up liquid first, with a 10 to 15 minute dwell, then scrub. For stubborn grease, an alkaline degreaser made for kitchens can help. Check that it is suitable for tile and grout, and rinse it away completely. A paste of bicarbonate of soda and washing-up liquid, covered with cling film and left for a few hours, works on set-in grease. Avoid acid cleaners near stainless steel, which they can mark; our pages on cleaning stainless steel and a stainless steel sink explain what they tolerate.

Rust marks

Orange-brown marks come from metal fittings, cans or tools left on wet surfaces. Rust removers based on oxalic acid work, but they are corrosive, so ventilate, wear gloves and follow the label, and keep them off natural stone. A lemon-juice rub may fade very light marks. Remove the cause as well, or the stain returns.

Set-in stains that nothing has shifted

Escalate gradually. Start with detergent, then oxygen bleach with a longer dwell, repeating over several days rather than going stronger in one session. Hydrogen peroxide under cling film is the next step. If a stain is still there after all that, it is probably in the grout for good, and a grout pen or regrouting is the answer. Persistent, deep, dark marks can also mean water has been getting behind the tile.

Mistakes that make grout worse

• Using acid on cement grout again and again. It slowly dissolves the surface, which then stains faster.
• Scrubbing with wire, a hard knife tip or a metal scraper. The grout line gets deeper and rougher and the tile glaze scratches.
• Mixing products to get more power. Bleach with acid or ammonia makes toxic gas, and mixing rarely helps anyway.
• Leaving cleaner to dry on the grout. It becomes harder to rinse and can leave a residue that attracts dirt.
• Skipping the rinse. Detergent and bicarbonate left behind form a film.
• Sealing damp or dirty grout. It traps moisture and stain under the sealer.
• Treating the stain and ignoring the cause. Constant damp, leaks or poor ventilation will bring mould back.

Kitchen cupboard tricks: what is worth trying

Lemon juice, salt, toothpaste and similar tricks turn up in plenty of cleaning advice. Lemon juice is a weak acid, so it behaves like a mild version of vinegar and carries the same risk to cement grout and natural stone, and the evidence that it bleaches grout is thin. Salt makes an abrasive scrub that can scratch. Toothpaste contains abrasives and colouring that can leave residue in the pores. None of them beats a proper detergent, oxygen bleach and a brush, so keep them for emergencies, and stay away from essential oil sprays, which add smell but not cleaning power. For more on the limits of natural cleaners, see our other cleaning explainers.

Sealant lines are not grout

The flexible line where a bath, shower tray or worktop meets the tile is silicone sealant, not grout, and it needs different treatment. Silicone can grow mould that works into the material itself, and once it is blackened right through no cleaner will bring it back. The usual answer is to cut out the old sealant and apply new sanitary silicone, after the surface has been cleaned and left completely dry. Do not use grout cleaners with strong acid on silicone. Do not use sealer on it either. If you are cleaning a shower tray surround, take a minute to work out which lines are grout and which are sealant.

Floors and big areas

On floors the problem is scale, so plan the work. Clear the room, sweep or vacuum thoroughly, and do a section at a time with a bucket of cleaner and a second of clean rinse water. Scrub with a long-handled grout brush or an electric scrubber with a soft-to-medium brush head, wipe up the dirty liquid with a mop or a wet vacuum, and rinse before it dries. Dirty rinse water re-soils the grout, so change it often. Keep the area closed until it is dry, because wet tile is slippery, and ventilate the room. A knee pad saves your joints if you are scrubbing by hand.

Fresh grout: haze and white powder

New grout often leaves a cloudy haze on the tile surface as it dries, and white powdery deposits can appear on new cement grout as it cures, called efflorescence. Both are normal. Wipe haze away with water and a soft cloth at the right time, and use a haze remover that is suitable for your tile if it has set. Do not use acid on new grout until the grout maker says it has cured enough, and let it cure fully before you seal it or use strong products. Following the instructions for the specific grout is the best protection.

Children, pets and shared spaces

Keep children and pets out of the room while you use bleach, acid cleaners or any other strong product, and until the area is rinsed and dry. Store products in their original containers out of reach, with the child-resistant caps on, and wash your hands when you finish. Open the window and leave the fan on for a while afterwards.

Room by room

Bathrooms need the most attention because they are damp. Improve ventilation first, then clean: a mould treatment on a damp wall only works for as long as the wall stays dry. In kitchens, deal with grease early, because it holds dirt and turns sticky, and avoid leaving citrus or vinegar sitting on grout near the hob. On floors, the key habit is sweeping before mopping, and avoiding dirty mop water. Our guide to cleaning old tile floors goes through those in detail, and the more general home pages are a good starting point for other rooms. For jobs involving heat and fumes, such as oven cleaning, the same ventilation and glove rules apply, and for people who like a methodical approach, keeping a note of what you used and when, as with washing machine maintenance, makes it easier to see what works.

Wet areas are where the drying habit pays off most. Wipe shower walls and the bottom row of tiles after use, run the fan during and after showers, and leave the door or curtain open to air. Our guide to cleaning windows without streaks shows the squeegee technique that works just as well on tiles.

Sealing and keeping grout clean

A penetrating grout sealer fills the pores in cement grout so liquids bead up instead of soaking in. It does not stop grout getting dirty, but it makes stains sit on the surface where they can be wiped away. Clean and dry the grout fully first, because sealing over dirt or damp traps it. Follow the sealer maker’s advice on when to apply after new grout, which is usually after it has cured for a few days or longer, how to apply (usually with a small brush or applicator bottle), how long to leave it and when to wipe excess off the tile faces. Reseal when water stops beading, which could be every year or two in showers and floors and less often elsewhere. Do not rely on a fixed schedule: use the water test.

How to seal grout, step by step

1. Clean the grout and let it dry fully, which can take a day or more in a damp bathroom. Do not seal while the lines are still damp.
2. Choose a penetrating (impregnating) sealer suited to cement grout and your tile, and read the label for coverage, drying time and whether it is suitable for walls, floors or wet areas.
3. Apply a thin, even coat along the grout with a small brush or applicator, keeping off the tile faces where you can.
4. Wipe excess off the tile surface within the time the label gives, because dried sealer on glazed tile can leave a haze.
5. Let it cure for the time stated before the area gets wet, which is usually at least a day, and apply a second coat if the maker says so.
6. Do the water test again a day or two later. If water still soaks in, add another coat.

Other useful habits: switch to liquid soap, which leaves less scum than bar soap, avoid leaving wet towels and bath mats on the floor, use a bath mat that can be washed, and fix dripping taps and leaking seals promptly. Keep the fan itself clean, since a clogged fan does little.

When cleaning is not the answer

• Cracked, crumbling or powdery grout. Water can get behind the tiles. Rake out and replace the damaged grout, or get a tiler to do it.
• Missing grout or loose tiles. Leave them alone until repaired, since moisture behind the tile can rot walls and floors.
• Stains that survive several treatments. They have probably gone through the full depth of the grout. A grout pen or regrouting is the fix.
• A musty smell that persists after cleaning. There may be damp behind the tiles. Look for leaks, failed sealant and condensation problems, and get a professional opinion.
• Large areas of mould, or mould that keeps coming back. Treat the cause. If there is a leak or structural damp, a plumber, builder or damp specialist is needed.
• Epoxy grout, delicate natural stone or a rental. Check with the manufacturer, the stone supplier or your landlord before you use anything strong.

What regrouting involves

Regrouting means removing the old grout to most of its depth and filling the joints with new material. For a small area, DIYers use a manual or oscillating-tool grout removal blade, working carefully so they do not chip tile edges. The joints are then vacuumed and cleaned, new grout is pressed in with a rubber float at an angle across the joints, excess is cleaned off the tile faces before it sets, and the lines are shaped and left to cure. A grout haze is wiped off once it dries. Colour matching new to old is hard, which is why many people regrout whole walls or floors rather than patches. In a shower or wet room, if you find soft plaster, rot or a failed waterproofing layer under the tile, stop and get a qualified tiler or builder.

Professional grout cleaning and regrouting services exist, and prices vary widely with the size of the job and the region, so get more than one written quote and ask what is included. Ask about insurance, the products used and whether sealing is part of the price. Be wary of anyone promising a particular percentage of stain removal. Regrouting is a skilled job in a wet room, because the waterproofing behind the tile matters. A homeowner who is comfortable with DIY can rake out and regrout small areas with a grout saw and fresh grout, taking care not to chip tile edges.

Questions to ask a professional before booking

• What exactly will you do, and which products and equipment will you use on my type of grout and tile?
• Do you carry public liability insurance, and can I see evidence?
• Will you test a small area first, and what will you do if the stain does not come out?
• Is sealing included, and which sealer do you use?
• What is the total price in writing, including any extras for mould treatment or repairs?
• How long before the area can get wet or be walked on, and what aftercare do you advise?

Choosing a method: the verdict

In other words, start gently, give each product the time stated on the label rather than more force, and change one thing at a time so you know what worked. A stiff brush and an extra grout brush kept for the job, an oxygen bleach cleaner and a pen for the final touch-ups cover most households. As an Amazon Associate we earn from qualifying purchases.

Three grout questions

How often should grout be cleaned?

A quick wipe after showers and a weekly mild clean keep wet-area grout in good shape, with a deeper clean monthly or when staining appears. Kitchen grout needs a regular grease wipe. Act quickly on mould, which is much harder to shift once it sets.

Can I use bleach on grout?

On white grout with mould, diluted chlorine bleach is an option, used with ventilation, gloves and a good rinse, and never mixed with other products. It can fade tinted grout and weaken sealer with repeated use, so oxygen bleach is the safer first choice for most grout.

Why does my grout get dirty so quickly after I clean it?

Usually because it is unsealed or the sealer has worn, so it soaks up water and dirt, or because the room stays damp. Check with the water test, reseal clean dry grout, improve ventilation and rinse cleaning products away completely.