Can You Tile Onto Plaster? Yes, Up to 20kg per m²

Can you tile onto plaster? Yes, as long as the plaster is sound, fully dry, primed and not painted, and the finished tiling weighs no more than 20kg per square metre including adhesive and grout. That weight limit is the one most people never check, and it is the reason big porcelain tiles slide off skimmed walls a year after they went up. This page covers the weight sum, the drying times, what to do about paint, and the point where you should stop and board the wall instead.

Plasterboard is a separate question with a higher limit, and it has its own page: can you tile onto plasterboard. Here we are talking about gypsum plaster: a backing coat and skim on brick or block, or a skim coat over plasterboard, which is what most Bromley and south east London houses have on their kitchen and bathroom walls.

The 20kg per m² rule, and how to work out your tiles

Topps Tiles’ substrate preparation guidance gives these maximum loads for wall tiling:

Gypsum plaster (or plasterboard with a plaster skim): up to 20kg per m²
Bare plasterboard, no skim: up to 32kg per m²
XPS foam boards such as wedi: up to 120kg per m²
Cement boards such as HardieBacker: up to 200kg per m²

The 20kg figure is the total load: tile plus adhesive plus grout. Topps advises adding 3kg per m² for the adhesive and grout, which leaves you 17kg per m² for the tile itself.

You will rarely find “kg per m²” printed on a tile, but every box lists its weight and its coverage. Divide one by the other. For example, a box that covers 1.44m² and weighs 25kg works out at about 17.4kg per m². Add the 3kg and you are at 20.4kg per m², just over the limit for plaster. That is a tile you would hang on board, not on a skimmed wall.

As a rough guide, thin ceramic wall tiles usually come in comfortably under the limit, while most porcelain at 9mm to 10mm thick lands close to it or over it. Large format porcelain, natural stone and split face panels are almost always too heavy for plaster. Do the sum with your actual box before you buy adhesive, not after.

New plaster: how long to wait before tiling

Tiling onto plaster that is still damp traps the moisture behind an impervious layer, and the bond suffers. The waiting times in the Topps guidance are:

New backing coat and skim on masonry: at least 4 weeks
New skim coat over plasterboard: at least 7 days

Those are minimums in a heated house with some air movement. A freshly plastered bathroom in November with the window shut and no heating on will take longer. Plaster that has dried properly is an even pale pink or light brown all over; dark patches mean it is still wet in that spot. A cheap moisture meter takes the guesswork out of it.

If you are short on time, this is the strongest argument for boarding the wall instead of replastering it. A cement or foam backer board can be tiled as soon as it is fixed and its joints are taped.

Prime the plaster before you tile

Gypsum plaster is porous and dusty, and gypsum can react with cement-based adhesives where they meet. A primer seals the surface, binds the dust and keeps the two apart. Topps says all plaster surfaces should be primed undiluted with BAL Prime APD when you are using a BAL cement-based powder adhesive, and diluted 1:1 with clean water when you are using a BAL ready-mixed adhesive. Other adhesive makers have their own primer and their own ratios, so match the primer to the adhesive brand and follow its data sheet.

Let the primer dry fully before the first tile goes on. The full table of which surfaces need priming, and at what dilution, is on our tile primer page.

Can you tile onto painted plaster?

Not safely. The Topps guidance on tiling onto painted surfaces quotes BS 5385-1:2018, the British Standard for internal wall tiling, which says painted surfaces are generally unsuitable for tiling and that emulsion, limewash, distemper and similar finishes should be removed because they can have poor adhesion to the backing.

The practical problem is that emulsion is water based. Wet adhesive softens it, so the tile ends up stuck to a layer of paint that is only loosely stuck to the wall. On top of that, ready-mixed adhesive is limited to smaller tiles, and cement-based adhesive is not recommended over paint, so there is no adhesive that gets you round it on a typical modern wall tile.

Removing it:

Steam: holding a wallpaper steamer against the wall softens emulsion so it scrapes off. This is usually the quickest way on plaster.
Score and scrape: cross-hatch the paint with a sharp knife first so the scraper can get under it.
Clean and key: wipe off any residue with warm water and a mild cleaner, then roughen the surface with abrasive paper so the primer and adhesive have something to grip.

On a skimmed plasterboard wall, go gently. Scraping too hard can tear the paper face of the board underneath, and once that happens the wall needs boarding over anyway.

Signs the plaster itself is not good enough

Dry, primed, paint-free plaster is still only as strong as its bond to the wall behind. Check it before you start:

Tap test: knock across the wall with your knuckles or a screwdriver handle. A hollow or drummy sound means the plaster has come away from the brickwork in that area. Tiles will add weight to a patch that is already loose.
Scratch test: if a key or screwdriver gouges the surface easily, or it powders, the plaster is too soft to carry tiles. Old lime plaster in Victorian and Edwardian houses often fails this.
Cracks and bulges: fine hairline cracks can be filled. Wide cracks, bulges and crumbling edges mean the plaster should come off.
Damage from old tiles: pulling old tiles off nearly always rips chunks out of the skim. Small holes can be filled and primed; large torn areas need patching or a new skim, and then the 4-week wait.
Flatness: plaster that is out of true by more than a few millimetres over a 2m straight edge needs dealing with before you tile. Our page on levelling an uneven wall before tiling covers the options.

Showers and wet areas

Gypsum plaster loses strength when it gets wet. Grout and tiles are not waterproof on their own, so inside a shower enclosure the plaster needs a tanking system over it, or it needs replacing with a cement or foam board that will not soften. Behind a basin or a kitchen splashback the occasional splash is fine on primed plaster. Inside a shower, where water hits the wall every day, we board it. More on that in our guide to tanking before tiling.

Applying adhesive to plaster

Once the wall is dry, sound, stripped and primed, the fixing is straightforward.

Square-notch tiling trowels in several sizes on a shop display — Square-notch trowels in different notch sizes; bigger tiles need a bigger notch | Trowels of various sizes and shapes, square notch trowels, in German hardware store (cropped) by Pittigrilli (CC0), via Wikimedia Commons, https://commons.wikimedia.org/wiki/File:Trowels_of_various_sizes_and_shapes,_square_notch_trowels,_in_German_hardware_store_(cropped).jpg

Choose the adhesive for the tile, not the wall: ready-mixed tubs are only suitable for small, light wall tiles. For porcelain, or anything larger than around 30cm by 30cm, use a cement-based powder adhesive with the matching primer.
Use the right notch: a square-notch trowel sized to the tile gives an even bed. Bigger tiles need a bigger notch.
Get full contact: press each tile in and slide it slightly to collapse the ridges. Lift one now and then to check the back is covered.
Work from a batten: fix a level timber batten one tile up from the floor or bath and tile upwards from it, so the weight of the wet tiles sits on the batten, not on the adhesive alone.

When to board the wall instead

Tiling onto plaster is fine for most bathrooms and kitchens with standard ceramic or light porcelain wall tiles. Board the wall with cement or foam backer board when:

your tile, adhesive and grout add up to more than 20kg per m²
the area is inside a shower or wet room
the plaster fails the tap or scratch test over more than a small patch
it is new plaster and you cannot wait 4 weeks
the paint will not come off without tearing the surface

Our tile backer board page covers which board, which thickness and how to fix it. If you would rather have someone check the wall and tell you which way to go, Bromley Tilers works across Bromley and south east London.

Frequently asked questions

Can you tile straight onto new plaster?

Not straight away. A backing coat and skim on masonry needs at least 4 weeks to dry, and a skim over plasterboard needs at least 7 days, before it is primed and tiled. Longer in a cold or unventilated room.

What is the maximum tile weight for a plastered wall?

20kg per m² for the whole lot: tile, adhesive and grout. Allow about 3kg per m² for adhesive and grout, which leaves roughly 17kg per m² for the tile. Divide the box weight by the box coverage to get your tile’s figure.

Do I need to remove paint before tiling onto plaster?

Yes. BS 5385-1 says emulsion, limewash and distemper should be removed because they can bond poorly to the backing. Water-based emulsion also softens under wet adhesive. Steam or scrape it off, clean and key the plaster, then prime.

Can you tile onto old lime plaster?

Only if it is hard, firmly attached and passes a scratch test, and only with light tiles. Much old lime plaster is soft or partly detached, in which case it should be removed or the wall boarded.

Can I use PVA to prime plaster before tiling?

Adhesive makers advise against it under cement-based adhesive. Use the primer recommended by your adhesive’s manufacturer, at the dilution on its data sheet.

Is a skimmed wall better than bare plasterboard for tiling?

No, it is the other way round. A plaster skim lowers the limit from 32kg per m² on bare plasterboard to 20kg per m², and it adds a drying wait. If you are planning heavier tiles, ask for the board to be left unskimmed in the tiled area.

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