Regrouting bathroom tiles: the right way, and the fast way

Nothing makes a bathroom look tired like old grout. You can replace the taps, put up a new mirror, buy a nice bath mat, and it still looks like 1998 because the grout lines are grey where they used to be white. Good news: fresh grout takes an afternoon and costs under £20. Here's how to do it properly.

First, work out if it's just grout

Tap a tile with your fingernail. If it rings clean and hollow, the tile's still well bonded. If it sounds dead and soft, water's got behind it, and you've got a bigger job than regrouting. Hollow tiles need lifting and reseating. If you've got hollow tiles, stop reading this and call someone.

Most of the time, though, the tiles are fine. It's just the joints between them that have had it.

Tools you'll need

• A grout rake or grout removal tool. The oscillating multi-tool with a grout blade is the quickest.
• A Stanley knife with a fresh blade for edges and corners.
• A grout float (the rubber-edged trowel thing). £5 at any builders' merchant.
• A bucket and sponge.
• Waterproof grout, not standard grout, for anywhere wet. White is safer than grey in a small bathroom.
• Masking tape for protecting any edges you don't want grout on.

The job, start to finish

1. Rake out the old grout

Work slowly. You want to get about 3mm of old grout out of every joint. Don't try to remove every last trace. Get most of it. The new grout bonds to what's left, that's fine.

Around tile edges, shower trays, baths, windows, stop and use the Stanley knife. Take old silicone out separately, the rake will ruin the edge.

Allow an hour on a small shower enclosure, two on a full bathroom. It's dusty. Dust sheet the floor. Wear safety specs.

2. Vacuum everything

Every joint needs to be clean and dust-free before the new grout goes in. Vacuum the joints. Wipe the tiles down with a damp cloth. Let them dry.

3. Mix and apply

Mix grout to a thick peanut-butter consistency. Too wet and it runs. Too dry and it crumbles.

Load the float at 45 degrees. Drag it across the tiles diagonally, pushing grout firmly into every joint. Don't dab it on, force it in. Work in metre-square sections.

4. Clean as you go

Wait 10 minutes until the grout just starts to firm up. Then, with a damp sponge, wipe the tiles clean in gentle circular motions. Rinse the sponge in a bucket regularly. This is the step most people rush. Take your time. The sponge is shaping the finished joint.

Second pass 20 minutes later with a drier sponge to polish off any final haze.

5. Leave it alone

24 hours before you run the shower. 48 hours before you silicone the edges (next step). Don't be tempted to hurry this. Fresh grout that gets wet too early gets streaky.

The silicone corners

Where the tiles meet the bath, shower tray, windowsill, or floor, don't use grout. Grout is rigid. Those joints flex. You need silicone there. Lay a line of masking tape either side of the joint, run a bead of bathroom silicone, smooth it with a wetted finger or a proper silicone tool, peel the tape off straight away. Clean line, no mess.

Costs if you want me to do it

• Shower enclosure only, regrout and silicone: 2.5 to 3 hours. Around £110 plus materials.
• Full bathroom, all joints: 5 to 6 hours. Around £180 plus materials.

Honest confession: my own bathroom grout is three years overdue. The cobbler's children and all that. I keep meaning to. Someone will remind me when they read this.