How to clean grout so it looks new again

How to Clean Grout So It Looks New Again: A Pro’s Guide to Stains, Mould, Colour and Sealing

There are few household jobs as quietly demoralising as scrubbing tile grout. It’s the thin lines you barely notice when they’re clean and can’t stop seeing when they’re grey, patchy, or speckled with black.

The good news is that grout is more fixable than it looks. With the right cleaner, the right brush, and a little patience, you can bring those lines back to crisp, near-new brightness without wrecking your tiles.

What grout is, and why it looks dirty so fast

Grout is a cement-based filler designed to bond tiles and keep water out. It is intentionally porous, which makes it excellent at gripping tiles and frustratingly good at gripping dirt. Soap, body oils, spilt coffee, even tap water minerals creep into those pores and dull the surface.

Many people don’t realise that not all grout is the same. Cement-based grout stains easily but can be renewed and sealed; epoxy grout is far less porous and resists staining, but still needs proper cleaning. Natural stone tiles add another layer of caution, because acids that are harmless to ceramic can etch marble or limestone.

Prep first: diagnose your surface and protect yourself

Decide what you’re standing on. If your tiles are ceramic or porcelain, you can use a wider range of cleaners. If they’re natural stone such as marble, travertine or limestone, avoid vinegar, lemon and other acids, and lean on pH-neutral or mildly alkaline cleaners only.

Open windows, wear gloves, and test any cleaner in a discreet corner. Grout can vary by age and colour, so a quick patch test avoids nasty surprises.

The quick routine clean most people skip

Grout responds brilliantly to a simple, regular wash. Mix warm water with a few drops of mild washing-up liquid and scrub along the lines with a stiff nylon grout brush or an old toothbrush. Work in short sections so you don’t let dirty water dry back into the pores.

Rinse with clean water and towel-dry the joints. Drying seems like a faff, but it’s the trick that stops residues from wicking back up and leaving a faint film.

For kitchens, think alkaline and dwell time

Kitchen grout often looks greasy rather than grey. A mildly alkaline cleaner lifts cooking films better than anything else. Mix a teaspoon of washing-up liquid or a capful of an all-purpose cleaner into a bowl of very warm water, apply generously, and give it five minutes to soften the grime before you scrub.

If stains linger, make a paste of baking soda and water, about three parts soda to one part water. Spread it on the lines, leave for 10 minutes, then scrub and rinse very well. The paste is gently abrasive and excellent for tan coffee or curry shadows.

For bathrooms, target soap scum and moisture

Bathroom grout faces soap, shampoo and constant damp. A solution of warm water and a little washing-up liquid works for routine mess, but you’ll get further by pairing it with a rinse of white vinegar on ceramic or porcelain tiles. Use a 1:1 mix of vinegar and water, let it sit for a few minutes after washing, then rinse again with clean water and dry.

Avoid vinegar on natural stone. If your tiles are marble or limestone, use a pH-neutral bathroom cleaner and skip the acid step. The goal is to remove scum without etching the surface around it.

Mould and mildew: choose peroxide or diluted bleach

Those pinprick black spots? That’s mildew taking hold. For light to moderate growth, hydrogen peroxide (3%) is more effective than many expect. Spray it directly on dry grout, leave for 10 minutes so it can fizz into the pores, then scrub and rinse. Peroxide both lifts the stain and helps neutralise spores.

For stubborn black mould, a diluted household bleach can be appropriate on white cement grout and ceramic tiles. Mix one part standard bleach to ten parts water, apply carefully with ventilation, allow up to 10 minutes of contact, then scrub and rinse twice. Never mix bleach with vinegar or ammonia, and never use it on coloured grout, natural stone, or epoxy grout. If in doubt, choose peroxide; it’s safer for more surfaces.

Deep stains and the case for oxygen bleach

If your grout has gone uniformly grey, oxygen bleach is the quiet hero. Sold as a powder that activates in warm water, it’s less harsh than chlorine and brilliant on organic stains. Dissolve a tablespoon in a litre of warm water, flood the grout lines, and let it dwell for 10 to 15 minutes before scrubbing and rinsing.

The key is to keep the lines wet during that dwell. Reapply solution rather than letting it dry. This is where many cleaning attempts fail: scrubbing too soon and giving up before the chemistry has time to work.

The right brush, pressure and technique

Grout needs firmness, not fury. Choose a stiff nylon brush with bristles that match the groove width. Work the brush at a shallow angle along the joint rather than across it. This drives cleaner into the pores rather than flicking it onto the tile surface.

Avoid metal brushes and harsh abrasives. They can gouge grout and create more places for dirt to cling. If you have epoxy grout, which feels smoother and less porous, lean on gentle detergents and a soft brush; heavy abrasives will scuff the surface.

When steam cleaning makes sense

A handheld steam cleaner can be impressive on greasy film and soap scum, especially on ceramic and porcelain. The heat softens residues and helps lift them out of the pores without chemicals. Move slowly so the steam has time to work, and always wipe as you go to remove loosened grime.

Skip steam on cracked grout, newly sealed areas, or soft natural stone. If you see water beading in the joint rather than soaking in, there may be sealer present, and steam could force moisture behind tiles. In that case, stick to surface cleaning and allow extra drying time.

Dry, then lock it in: sealing makes the difference

Freshly cleaned grout looks best when it stays that way. Once the lines are fully dry, apply a penetrating grout sealer on cement-based grout to slow future staining. Most products want the grout bone-dry, which can take 24 to 48 hours after a deep clean. Plan for that window.

Choose a clear, breathable sealer and apply with a small brush or applicator bottle, wiping stray drips off tiles quickly. Two thin coats often outperform one heavy coat. Epoxy grout does not need sealing; it’s already highly stain-resistant.

Colour-seal to reset the clock

If your grout has uneven shading you can’t shift, colour-sealing is a surprisingly simple reset. It’s essentially a tinted sealer that adds a uniform colour while protecting the surface. Clean thoroughly, let it dry completely, then brush on the colour-seal and buff away excess on the tiles before it cures.

This step hides stubborn ghosting and gives you a crisp, consistent look. It also buys you time between deep cleans because stains have a harder time sinking in.

How to keep it clean with minimal effort

A little prevention is worth a lot of scrubbing. In showers, a quick squeegee and a towel wipe after the last use of the day removes the film that feeds mould. In kitchens, wipe splashes quickly and do a weekly wash of grout lines with warm soapy water before they grey.

Ventilation matters more than most people think. Run an extractor fan during and after hot showers, and leave doors open to reduce lingering moisture. Dry grout doesn’t mould easily.

Common mistakes to avoid

Rushing the dwell time is the number one error. Cleaners need minutes, not seconds, to break bonds with the dirt. Flood the lines, wait, then scrub.

Overusing acids is the second. Vinegar has its place on ceramic and porcelain, but it will etch natural stone and can weaken cement grout if used neat and often. Keep acids dilute and occasional, and choose oxygen bleach or peroxide for deep cleans instead.

When to repair rather than just clean

If grout is crumbling or cracked, no cleaner will fix it. Pick out loose sections with a grout saw, vacuum the dust, and regrout the gap. New grout bonds best to clean, dry tile edges, so do the messy part first and the beauty clean after the repair has cured.

If lines have sunk below the tile edge and catch dirt, topping up with fresh grout or using a colour-seal to fill micro-pits can dramatically reduce future staining. Sometimes “looking new again” is as much about sound joints as sparkling ones.

A final word on patience and pay-off

Grout gives up its stains slowly and then, all at once. The combination of the right cleaner for the mess, a proper dwell, and a steady brush produces results that feel unfairly satisfying. Once you’ve brought the lines back, a seal and a quick weekly wipe will keep them that way far longer than you might expect.

Cleaner, brighter grout lifts the whole room. It’s not glamorous, but it is one of the rare domestic jobs where an hour’s methodical work can make a space look freshly renovated.