Regrouting is worth it when the tiles are sound — it's the cheapest way to take years off a tired bathroom. Rake out the old grout, regrout cleanly, seal it, and a grubby, cracked, mouldy-looking wall comes back to life for the price of a bag of grout. But if the tiles are loose or the wall behind them is soft, fresh grout is lipstick on a pig. Here's how to do it right, and how to tell which job you've actually got.
Key Takeaways
- Regrout if the tiles are sound — it's a weekend and a bag of grout vs a full re-tile.
- Re-tile instead if tiles are loose, drummy (hollow-sounding), or the wall is soft.
- You can't grout over old grout — rake it out to depth first, or it cracks straight back out.
- Keep the rake in the centre of the joint to protect the tile edges.
- Silicone the movement joints, seal the cement grout, and let everything cure.
First: should you regrout or re-tile?
Be honest about this before you buy a thing, because regrouting a wall that's on its way out is wasted effort.
Regrout if:
- The tiles are firmly stuck and don't move.
- The grout is just discoloured, cracked in places, or mouldy — but the tiles themselves are fine.
- Tapping the tiles gives a solid sound across the wall.
Re-tile instead if:
- Tiles are loose, lifting, or drummy — tap them and they sound hollow, which means the adhesive's let go behind.
- The wall behind feels soft or you can see water damage — that's a substrate problem fresh grout won't touch.
- Grout is failing everywhere because the wall moves, or there was never any tanking behind a shower.
A quick test: tap across the tiles with your knuckle or a coin. A consistent solid note means they're well bonded. A hollow, drummy note in patches means the bond's gone there — and no amount of new grout fixes a tile that's already let go. If a shower wall is failing because it was never waterproofed, the real fix is a strip-out and proper tanking, not regrouting.
Step 1: Rake out the old grout
This is the graft, and the step people skip at their peril. You cannot grout over old grout — new grout needs depth to bond, so a thin skim over the top just cracks and drops out within months.
- Use a grout rake (a hand tool) or, far quicker on a whole bathroom, an oscillating multi-tool with a grout-removal blade.
- Keep the blade in the centre of the joint, away from the tile edges — that's how you avoid chipping tiles.
- Rake out to a decent depth — at least 2mm, more if you can — so the new grout has something to key into.
- Vacuum and wipe the joints clean afterwards. Dust in the joint stops the new grout bonding.
Take your time near the edges. An electric tool is fast but unforgiving if it wanders onto a tile.
Step 2: Choose the right grout
Don't just grab whatever's nearest. Grout choice matters as much here as on a new job:
- Joint width decides sanded vs unsanded — sanded for wider joints, unsanded (fine) for narrow ones.
- Wet areas want a grout built for it — a polymer-modified or flexible grout resists water and movement better than basic cement grout, and many come with anti-mould protection that keeps a bathroom looking fresh longer.
- Match the colour if you're regrouting part of a wall — or regrout the whole wall so it's consistent, because old and new grout rarely match.
The full breakdown of types and where each belongs is in how to choose tile grout.
Step 3: Regrout
Same technique as a fresh job:
- Mix the grout to a firm, lump-free paste — a slow-speed mixer beats mixing by hand.
- Work it into the joints with a grout float held diagonally, pressing it in fully so there are no gaps.
- Scrape off the excess diagonally across the joints so you don't drag grout back out.
- Clean the haze off the tile faces with a damp (not soaking) sponge before it dries. If you leave a film, grout haze removal sorts it.
Step 4: Silicone, then seal
Two finishing jobs that decide how long the result lasts:
- The moving joints get silicone, not grout — where the wall meets the bath, tray, or worktop, and internal corners. Rake out any old failed silicone, let the area dry, and run a fresh bead of mould-resistant sanitary silicone. Grout in these joints cracks every time.
- Seal the cement grout once it's fully cured (check the bag — usually a day or more). A grout sealer resists staining and water in a wet bathroom and keeps the joints looking fresh.
The honest verdict
Done on sound tiles, regrouting is one of the best-value jobs in a bathroom — a weekend's work that looks like you spent far more. Done on a wall that's already failing, it's money and effort you'll spend again within a year. Make the regrout-or-re-tile call honestly first, and if it's a regrout, the result will outlast a rushed full re-tile any day.
For the whole job from scratch — when it really is time to re-tile — see the complete bathroom tiling guide.
Related guides
- How to choose tile grout — picking the right grout
- Grout haze removal — clearing the film
- How to tile a shower wall (and tank it) — when a failing shower needs stripping back
- The complete bathroom tiling guide — the full re-tile