Old grout makes new tile look old. Our bathroom tiles are 2014, white subway, and would have lasted another decade — but the grout was patchy, a few lines were brown along the bottom, and the whole bathroom read as needing a renovation. It did not need a renovation. It needed grout. One Saturday afternoon and fifteen euros of materials later the bathroom is the bathroom that the building plan promised.

Why re-grouting beats a renovation

A bathroom renovation is six thousand euros and three weeks of inconvenience. Re-grouting is fifteen euros and four hours. The difference, visually, is roughly seventy percent of the renovation. Tile that is intact and grout that is fresh reads as new — your eye registers the lines between tiles long before it registers the tiles themselves. Fresh grout, even on tired tile, looks like a new bathroom from anywhere more than two metres away.

Close-up of old discoloured grout between subway tiles, showing brown patches and uneven texture Save
Old grout. Patchy, uneven, eighty percent of the problem.

The other case for re-grouting is the cost-benefit. A typical small bathroom has roughly fifteen square metres of grouted surface — call it sixty linear metres of grout line. At a euro per metre of materials, that is sixty euros maximum. Most projects cost less. The labour is yours; the time is one afternoon. There is no other home-improvement project with the same return for the same investment.

How we did it

Step one was a grout saw, twelve euros, with a hardened steel blade. Step two was four hours of running the saw along every grout line, taking out the top three millimetres. Step three was vacuuming twice. Step four was mixing a small bucket of grout and pressing it into the lines with a rubber float at forty-five degrees. Step five was wiping the haze off with a damp sponge in three passes. Step six was leaving it overnight to cure. Step seven was a small celebration, twelve hours later, of a bathroom that had become its own newer version.

A grout saw, a rubber float, and a bag of cement-based grout laid out on a folded towel on a bathroom floor Save
Total kit: twelve euros of saw, three of float, five of grout.
“Fresh grout on tired tile reads as new from anywhere more than two metres away.” — Theo
  • Cement-based grout, never silicone. Silicone is for joints between two surfaces (tile-to-bath); cement is for tile-to-tile.
  • Sanded grout for lines wider than 3 mm; unsanded for narrower. Subway tile is usually unsanded territory.
  • Wipe haze in three passes, half an hour apart. One pass leaves haze; two leaves streaks; three is correct.
  • Cure for at least twelve hours before water hits it. Twenty-four is better.

What grout colour does to a small bathroom

We almost picked white. White grout in a bathroom is a six-month commitment to looking like a renovation, then a decade of looking dirty no matter how often you clean. We went with a warm light grey — one shade darker than we thought we wanted, two shades lighter than what looks 'industrial' — and the room reads softer, warmer, and stays consistent over time. The first shower mark on a grey grout line is invisible. The first shower mark on white grout sets the tone forever.

There is a wider design rule emerging here. In a small bathroom, every line is a graphic element — the grout lines outline the tile and create the room's grid. White grout makes the grid loud; matched-tone grout makes the grid disappear. Loud grids work in commercial bathrooms; quiet grids work in domestic ones. We wanted the bathroom to feel like a small room with tile in it, not a tile installation that happens to be a bathroom.

On the colour scale: warm light grey for warm-toned tile (cream, beige, off-white), cool light grey for cool-toned tile (true white, pale blue, sage). Brown grouts read as dirty even when fresh. Black grouts read as graphic but show every patch of imperfectly cleaned soap residue. Light to mid-grey is the safest answer for almost any tile colour and almost any bathroom.

What we did not re-grout (and why)

The vertical joint between the bathtub and the wall stayed silicone — that joint flexes as the bath warms and cools, and cement grout will crack within a season. Same with the joint between the basin and the wall, and the corners where two walls meet. These are 'movement joints' and silicone is the right material because it absorbs flex. The trick is to cut out the OLD silicone first, scrape the joint clean, and apply fresh — same logic as cement re-grouting, different material.

We also did not re-grout the floor. The floor grout was darker than the wall grout from the start, and a re-grout would have meant matching that colour exactly, which is harder than picking a fresh shade for the walls. The floor grout reads fine because the dust and use have aged it evenly. Sometimes the right answer is to leave the part that has aged together with itself, and only refresh the part that aged badly.

How to do it

Saw the old grout.

Three millimetres deep along every line. The saw makes the work — a screwdriver does not. Twelve euros, hardened steel. Goggles and a mask; cement dust is not friendly.

Saw the old grout.

Vacuum twice.

Once roughly, once with a brush attachment. Any dust left in the line will show up as a darker patch in the finished grout. Vacuum after, not before — debris settles.

Mix and press grout.

Powder to the consistency of thick cream. Press into lines with a rubber float at 45° to the joint. Work in patches of one square metre at a time so the haze cleanup happens at the right pace.

Three sponge passes.

Damp sponge, light pressure. Wait twenty minutes. Repeat. Repeat. By the third pass the lines are sharp and the tile faces are clear.

Frequently asked

Can I do this in a rental?
Yes — re-grouting is maintenance, not renovation. Most landlords prefer the bathroom looking fresh and will not object. Take a before photo so you have evidence the tile was already worn.
Will the new grout match the old?
If you bought a recognisable colour from a chain hardware shop, yes. The grout you remove was the same colour when new. To be sure, take a photo and compare in the shop.
How long does it last?
Eight to fifteen years before the next re-grout. Faster in a rental with kids; slower in an empty-nest flat.
Is epoxy grout worth the extra effort?
Only in commercial settings or pool surrounds. Residential bathrooms do not need the chemistry. Epoxy is twice the price, three times the cure time, and impossible to remove without rebuilding the wall. Standard cement grout is the right answer.
What about sealing the grout?
Cement grout in a bathroom does not need sealer if the room ventilates properly. A grout sealer adds an annual chore and rarely outperforms a well-ventilated bathroom that gets a quick wipe-down after showers.
Can I do this in stages — one wall at a time?
Yes, but match the grout from the same bag. Different bags can vary by a shade even within the same brand. Buy enough for the whole room at once and you will not regret it later.
Should I pre-soak the tiles?
Some old guides say yes; modern unsanded grout does not require it. A damp-but-not-wet tile surface is fine. Soaking the tiles wastes time and over-dilutes the grout at the line edges.
What about the smell?
Cement grout smells like wet cement for the first hour and is gone by the next morning. No off-gassing, no respiratory concerns once cured. The mask is only for the dust during sawing-out, not for the application.

In closing

The bathroom looks like a bathroom that was redone last spring, which is true in a small way. Fifteen euros, one Saturday, no plumber, no demolition, no upset cat. The most extravagant home improvement is rarely the most effective. Most rooms are one or two materials away from looking like themselves again.