How to Clean Grout, Properly

Tile is easy. Grout decides whether a bathroom reads as clean, and it is the part most cleans only pretend to do. If the lines still look grey after you have wiped the whole wall, the dirt is sitting below the surface.

Where grout sits in the rhythm of a house is covered in our full house cleaning schedule and checklist. This is the detail underneath it: what grout is, why it holds what it holds, and the method that gets it out.

Grout is porous, and that changes everything

Standard cementitious grout is a sand and cement mix with microscopic voids running right through it. Glazed tile is effectively glass. Water, soap residue, body oil and skin cells land on both, run straight off the tile and soak into the grout, where they stay. That is why a shower wall can look evenly clean except for a grid of grey lines.

Floor grout is usually sanded and coarser, so it holds more. Wall grout is finer. Epoxy grout is genuinely non-porous and behaves like plastic, though it is uncommon in older Brisbane homes, so assume yours is cement unless you know otherwise.

A wipe removes what is sitting on top. The discolouration lives 2 or 3 millimetres down, out of reach of a cloth.

What bleach actually does

It takes the colour out. Bleach is an oxidiser, so it strips the pigment from whatever it contacts. The stain stops being visible while the material producing it stays in the pores, and it comes back, usually faster each time, because the residue left behind gives the next round something to hold onto.

Bleach also arrives as a water solution, so every application puts more moisture into a wet room that is already struggling to dry out. If black speckling in the grout or silicone is the reason you reached for it, understanding why bathroom mould keeps returning is a better use of the afternoon. The goal is physically removing the growth, and bleach removes nothing from a porous surface.

If a product promises white grout with no scrubbing, what it is promising is bleach.

Work out which problem you have

Grout goes bad in several ways, and they do not respond to the same treatment. Look closely before you commit.

• Chalky white or cloudy film, worst around tapware and along the shower base: mineral deposit and soap scum. A mild acid dissolves it.
• Grey to brown, slightly greasy, worse in traffic paths and along the shower floor: body oil, skin and general soil. A mild alkaline cleaner shifts this better than acid.
• Black speckling in the silicone and along permanently damp edges: growth. It needs physical removal, and silicone that has gone black all the way through gets replaced.
• Yellow or tan tint that survives a thorough clean: usually a failed or discoloured sealer, or pigment the grout has taken up permanently. Cleaning harder will not shift it.
• Even discolouration across a whole floor with no pattern: quite possibly the grout colour. Check under a piece of furniture that has never been walked on.

The method that works

None of this is clever. It is sequence and patience, and every step earns its place.

1. 1Dry first. Vacuum or sweep the floor properly. Wetting loose grit turns it into a paste you then push around for 20 minutes.
2. 2Wet the surface with plain water. Product applied to bone-dry grout disappears into the pores instead of working on what is in them.
3. 3Apply your product along the grout lines themselves. A mild acid such as citric acid for mineral deposit and soap scum, a mild alkaline cleaner for oily soil.
4. 4Let it dwell for 5 to 10 minutes. This is the step people skip, and it is the one doing the chemistry. Do not let it dry out. Re-mist if the room is warm.
5. 5Scrub along the line with a stiff narrow brush. Short strokes, firm pressure, and keep going past the point where you think it is done.
6. 6Rinse thoroughly with clean water, then rinse again. Residue left in grout is tacky and attracts soil, which is why a badly rinsed clean looks worse in a fortnight.
7. 7Dry the area and get air moving. A squeegee and an open window beat anything in a bottle for keeping it that way.

For a whole shower, work in sections of roughly a square metre so nothing dries before you get to it. Slower, and the only way the result comes out even.

The brush matters more than the bottle

Most of the improvement is mechanical. A stiff nylon brush with a narrow head sits down inside the grout line, where a sponge or a flat cloth bridges over the top of it. Replace it once the bristles splay, because a splayed brush just polishes the tile either side.

Anything more abrasive has a place only where the surface can genuinely take it. Test in a corner behind the door first. Keep abrasives off glazed and polished tile faces, natural stone, acrylic bases and anything with a coating.

On stone specifically: marble, limestone and travertine etch on contact with acid, and the dull patch that results does not buff out at home. If you are not certain what your tile is, keep acids off it. Our piece on where vinegar and other acids genuinely earn their place covers which surfaces tolerate them.

Sealed or unsealed, and how to tell

Drop a little water onto the grout line and watch. If it beads and sits there, the seal is intact. If the grout darkens within 30 seconds, the sealer has worn off, which is normal in a shower after roughly 1 to 3 years of daily use.

Sealer soaks into the material, so there is nothing to see on the surface. Resealing has 2 requirements. It must go on grout that is genuinely clean, or you seal the staining in permanently. And it must go on grout that is genuinely dry, which usually means 24 to 48 hours after cleaning in a Brisbane bathroom, longer in a wet week. Sealing damp grout traps moisture where you least want it.

Damage that cleaning cannot fix

There is a point at which cleaning stops being the answer, and recognising it saves a lot of pointless effort.

• Grout that comes away as powder on the brush has lost its binder. It needs regrouting, and scrubbing accelerates the loss.
• Missing sections, hairline cracking or grout that has dropped below the tile edge means water is getting behind the tile. That is a repair, and a reasonably urgent one.
• Cracks along the junction where the wall meets the floor, or in an internal corner, usually mean rigid grout was used where a flexible silicone movement joint belongs. Regrouting it will crack again.
• Silicone that has gone black all the way through is finished. It gets cut out and replaced, and surface treatment on it is cosmetic at best.

Keeping it, once you have got it

Grout that is on top of things needs surprisingly little to stay that way: a squeegee after showers, ventilation, and a wipe of the grout lines during the weekly clean before anything has a chance to set.

That is how we handle it in practice. In a home we clean regularly, bathrooms including showers, grout, tiles, taps, basins and toilets are part of every visit, and that steady attention keeps grout looking right on its own. Where grout has been left for years, the heavy work belongs in a first reset deep clean, the same job list on surfaces that have been waiting, so everything takes longer. A reset on a 3 bedroom home runs to about 20 hours. That sounds like a long time, and it is how long it takes to do it well. Regular visits after that are much shorter. For the wider bathroom sequence, we have written up how to clean a bathroom in the right order.

We do all of this without bleach, without fragrance and without antibacterial agents, because a stiff brush, the right product for the surface and enough time make them unnecessary. Harsh chemistry is mostly there to make up for a lack of time, and a lower price usually means fewer hours in your home. We charge $85 per hour and spend the time.