How do I take old wall tiles off without destroying the plaster?

Accepting up front that the plaster usually comes off with the tiles, the method that limits the damage, and what to do with the wall afterwards.

Difficulty: intermediate
Time: 4 hr
Read: 5 min
Safety: warning

Short answer

Start by breaking one tile out to see what is behind, then work outwards with a bolster held at a shallow angle, prising rather than smashing. Expect the plaster to come with it in places — that is normal, not a mistake. Afterwards the wall is either patched, re-skimmed or re-boarded, and re-boarding is often quicker than chasing a bad skim.

Everybody wants to remove tiles and leave a clean flat wall, and it is worth knowing at the outset that this rarely happens. Modern adhesive on modern plaster is often stronger than the bond between the plaster and the wall, so the plaster loses. Planning for that outcome makes the job manageable; hoping to avoid it makes it miserable.

Safety

Tiles come off as sharp shards under tension and travel: full face protection, gloves and long sleeves, every time. Before starting, consider the age of the building — pre-2000 wall finishes and adhesives, and any textured coating behind, may contain asbestos and must not be sanded, ground or broken until assessed. Check for cables and pipes in the wall, particularly around sockets, switches and the bath. Chisel and grinder work generates silica dust: extraction and an FFP3 mask.

What you'll need

a wide bolster chisel and a lump hammer
full face shield and gloves
dust sheets and a rubble bag or two
an SDS drill with a chisel bit, for larger areas (optional)
a multi-tool or grout rake (optional)
a scraper and filler or plaster for making good

Step by step

Establish what is behind the tiles first.Break one tile out in an inconspicuous place. Plaster, plasterboard, backer board or bare brick all change the method and the expectations. Note the age of the house and stop if there is any suspicion of asbestos in the layers behind.
Isolate and protect everything you are keeping.Cover the bath or tray with thick board, not just a dust sheet — a dropped tile chips enamel and cracks acrylic. Tape over the plughole. Take out anything removable.
Rake out the grout on the first tile you attack.It gives the chisel somewhere to enter and it stops the first break running into neighbouring tiles unpredictably.
Work from the top down, and outwards from an opened edge.Gravity does the work and you are never reaching over an area you have already loosened. Once one tile is out, the next has an exposed edge to get behind.
Keep the bolster at a shallow angle to the wall.Almost parallel, sliding behind the tile. A chisel driven at the wall punches holes; a chisel driven along it lifts tiles off.
Use light repeated blows, not heavy ones.Heavy blows crack tiles into shards and drive damage into the plaster. Repeated light taps let the adhesive bond fail progressively.
Accept that the plaster is coming off in places.Where the adhesive bond beats the plaster bond, the plaster comes with the tile. Fighting that only produces more damage; take it off cleanly rather than leaving loose fragments.
Once tiles are off, scrape the wall back to sound material.Ridges of old adhesive, loose plaster and blown areas all have to go. Tap the wall: anything hollow will fail later, so remove it now.
Decide between patching, skimming and re-boarding.Scattered small damage: fill and skim. Widespread damage or hollow plaster: hack off and re-skim. Damage plus a wet area or a wall you were going to re-tile anyway: over-boarding or re-boarding is often quicker and gives a flatter, better surface.
Deal with what you found before covering it up.Damp, rotten timber, a leaking pipe or unsuitable board behind a shower are all things that are visible now and never again once the wall is closed.

Tips

An SDS drill in chisel mode with a wide bolster bit makes a big area vastly quicker — but it is far more aggressive, so keep it shallow and off any plasterboard you want to keep.
Tiles on plasterboard usually cannot be saved: the board's paper face comes away with them and the board has to be replaced.
Bag rubble as you go in small quantities. Tile rubble is dense and a big bag becomes unliftable.
If you are re-tiling anyway, over-boarding the wall gives you a fresh flat substrate without any plastering — often the fastest route to a good result.

Common mistakes

Smashing tiles face-on with a hammer — It shatters them into flying shards, drives the impact into the plaster rather than the bond, and produces far more wall damage than working behind the tile with a bolster. It is also the way people get cut faces and eye injuries.
Assuming the wall will be reusable — Planning the job around a clean wall means it feels like a disaster when the plaster comes off, and it usually will. Budget the time and the materials for making good from the start.
Skipping the asbestos question in an older house — Textured coatings, some old adhesives and old wall linings from before 2000 can contain asbestos, and breaking or grinding them releases fibres. It is one of the few DIY risks that cannot be undone, and an assessment is cheap by comparison.

If it doesn't work

Plaster coming off in large sheets

Cause: The plaster was already blown, or the adhesive bond exceeds the plaster bond — Fix: Take the loose material off deliberately back to sound edges rather than leaving fragments. Then decide between re-skimming and boarding.

Tiles will not budge at all

Cause: Fixed to a dense masonry or cement render background — Fix: This is the good outcome for the wall and the slow one for you. An SDS chisel is the practical tool; keep it shallow and work along the bond line.

Plasterboard paper torn off across the whole wall

Cause: Tiles bonded to the paper face — Fix: The board is finished — the paper is its strength. Replace the board rather than trying to skim over torn paper.

Questions people ask

Can I steam or soften the adhesive?

Not usefully with cement-based adhesive, which is a set cement and is not softened by heat or water. Old organic mastic adhesives sometimes respond to heat, but the method is still mechanical for anything modern.

Is it easier to just board over the old tiles?

Sometimes, yes. Over-boarding avoids the destruction entirely, but it adds thickness, needs fixings that reach through to something solid, and leaves you no view of what is behind. In a shower that has ever leaked, take them off and look.

How do I get the last of the adhesive off?

A scraper, a wide chisel or a multi-tool with a scraper blade for ridges, then filling any remaining unevenness. Do not sand it — old adhesive dust is exactly the kind of dust that needs an FFP3 mask, and in older properties it is also the kind you should not disturb at all until you know what it is.