Guide · by Mark Holt
Regrouting or retiling? How to tell
Most tired tiling needs new grout and silicone, not new tiles. Here's how to tell which yours needs, and what a proper regrout involves.
The short answer
If your tiles are firmly stuck, uncracked and dry behind, regrouting and resealing will usually put right what you can see, for much less than retiling. If tiles are loose, sound hollow, or water has got in behind them, new grout only hides the problem for a while. Those tiles need to come off, and sometimes the whole wall does.
The rest of this guide explains how to tell the difference yourself, before you spend anything.
What grout and silicone actually do
Grout fills the joints between tiles. It stops dirt collecting in the gaps and finishes the surface, but ordinary cement-based grout isn't waterproof: it's slightly porous, and water can pass through it slowly.
Silicone (a flexible sealant) goes where tiles meet a bath, shower tray, basin or worktop, and usually in internal corners. Those joints move slightly as the house warms, cools and takes weight, and grout there would crack.
In a well-built shower, neither of them is what keeps water out of the wall. That's the job of the tanking (a waterproof membrane system) behind the tiles. Grout and silicone still matter, because once they fail, water sits in the joints and, in an older shower with no tanking, gets into the wall itself.
Check the tiles first: the tap test
Before deciding anything, check the tiles themselves. Press firmly on each one in the shower area and around the bath. None of them should move.
Then tap them gently with something hard, like the handle of a screwdriver. A tile that's properly stuck sounds solid. One that has lost its bond sounds hollow or dull. One or two hollow tiles in a dry area aren't unusual and may be fine; a patch of them in a shower is a warning.
Signs a regrout will do
Regrouting and resealing is usually enough when:
The grout is stained or discoloured, but still hard and in place.
The grout is cracked or crumbling in places, and the tiles either side are firm.
There's mould on the surface of the grout that cleans off but keeps coming back.
The silicone has gone black, split or come away from the bath or tray.
You want a different grout colour. A full regrout can take a room from dark grout to light, or the other way round.
Signs it's time to retile, or at least lift some tiles
Look further than the grout when you see:
Tiles that move or sound hollow over a wide area, especially in the shower.
Cracks running in a line across several tiles. That usually means the wall or floor behind is moving, and replacing tiles won't stop it.
Grout that cracks again soon after it's repaired, along the same lines. That points to movement too.
Signs of water where it shouldn't be: stains on the ceiling below, damp or flaking paint on the other side of the wall, swollen skirting or door frames, or a musty smell that never clears.
A soft or crumbling wall behind a tile that's come away. Plasterboard and plaster that have stayed wet for a long time won't hold tiles again.
You simply don't like the tiles. A regrout makes them look cleaner, not different.
Mould: grout, silicone or the room?
Black spots on grout are usually mould. On the surface, a mould cleaner and a stiff brush often shift them. In silicone, mould grows into the sealant itself and can't be cleaned out, so the only fix is to strip it and reseal.
If mould comes back within weeks of cleaning or a regrout, the room isn't drying out between showers. An extractor fan that works and runs long enough, a window open after showering, and wiping down the screen and walls make more difference than any grout or sealant.
Cracked tiles
A single cracked tile, from something dropped or a knock, can usually be cut out and replaced without disturbing the tiles around it. It's much easier if you kept a few spares from the original job. If not, a close match can sometimes be found, but some older tiles can't be matched at all.
Cracks across several tiles, or along a line in a floor, are different. On a timber floor they often mean the floor flexes underfoot; on a wall they can follow a crack in the plaster behind. The cause needs fixing before any tiles are replaced, or the new ones will crack too.
What a proper regrout involves
A regrout that lasts takes longer than most people expect, because most of the work is getting the old material out.
The old grout is raked out to a proper depth, not scratched at the surface. New grout needs depth to grip, and a thin skim over old grout soon cracks out.
The joints are cleaned of dust and loose material.
New grout is packed in firmly and cleaned off the tile faces.
All the old silicone is removed, every trace, and the surfaces cleaned before new sealant goes on. Fresh silicone over old doesn't stick.
The shower stays out of use until the grout and sealant have cured, for as long as the products' instructions say.
That's how Mark does it: old grout raked out to a proper depth, and old silicone fully removed before resealing, so the repair lasts rather than lifting in a few months.
Cost: why the checks come first
Regrouting is usually much cheaper than retiling: there are no new tiles to buy, nothing to strip out and no walls to prepare. But if water has already got behind the tiles, money spent on new grout is wasted, because the tiles will have to come off anyway. That's why the tap test and the checks above come first.
Prices aren't published, because the time a regrout takes depends on the area, how hard the old grout is to remove and how much silicone there is to replace.
Still not sure?
Send Mark a few photos on WhatsApp or through the contact page: a close-up of the worst area, a wider photo of the whole wall, and anything you've noticed on the ceiling below or the other side of the wall. You'll get a straight answer on whether it needs a regrout or more.
More about regrouting and tile repairs.