How to Clean Grout, Properly

Tile is easy. Grout is the part that 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 entire wall, you have not failed at wiping. The dirt is simply not on the surface.

Where grout sits in the rhythm of a house is covered in our full house cleaning schedule and checklist. This is the technical 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, by contrast, is effectively glass. Water, soap residue, body oil and skin cells land on both. They 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, but it is uncommon in older Brisbane homes, so assume yours is cement unless you know otherwise.

A wipe removes what is sitting on top of all that. It does not touch the 2 or 3 millimetres underneath, which is where the discolouration actually lives.

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. The material producing the stain is still sitting in the pores, unbleached below the top layer, and it comes back looking exactly as it did before, usually faster each time because the residue left behind gives the next round something to hold onto.

There is a second problem. Bleach 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. Killing growth is the wrong goal. Physically removing it is the goal, and bleach does not remove anything 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 different ways, and they do not respond to the same treatment. Look closely before you commit.

• Chalky white or cloudy film, hardest around tapware and along the shower base: mineral deposit and soap scum. This is an acid job. Citric 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 concentrated in the silicone and along permanently damp edges: growth, not soil. It needs physical removal, and silicone that has gone black through is replaced rather than cleaned.
• Yellow or tan tint that survives a thorough clean: often a failed or discoloured sealer, or pigment the grout has taken up permanently. Cleaning harder will not shift it.
• Even discolouration across an entire 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 that 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 to the grout lines specifically, not the whole wall. Citric acid solution for mineral 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, not across it, 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 than no clean at all.
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. It is slower, and it is 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 simply bridges over the top of it. Replace it when the bristles splay, because a splayed brush is just an expensive way to polish the tile either side.

Steel wool has a place where a surface can genuinely take it, and no place where it cannot. Test in a corner behind the door before you commit to a wall. Keep it 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 resulting dull patch does not buff out at home. If you are not certain what your tile is, do not put citric acid on it. Our piece on where vinegar and other acids genuinely earn their place goes into which surfaces tolerate them.

Sealed or unsealed, and how to tell

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

Sealer is a penetrating treatment, not a coating you can see. 2 things about resealing matter. 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.

When it is damaged, not dirty

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 running 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, not cleaned. Surface treatment on discoloured silicone is cosmetic at best.

Keeping it, once you have got it

Grout that has been properly reset needs surprisingly little to stay that way: a squeegee after showers, ventilation, and a wipe of the grout lines during the normal weekly clean before anything has a chance to set. The heavy work is a single effort if the maintenance afterwards is honest.

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. The heavy grout work belongs in the first reset deep clean, which is not a different job list, just the same list on a house that has not had it done yet, so everything takes considerably longer. After that it stays on top of itself. If you want the wider bathroom sequence rather than grout alone, 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, citric acid and enough time make them unnecessary. Harsh chemistry is mostly there to compensate for minutes nobody paid for. We price the time instead, at $85 per hour.