Terrazzo Tiles: Real 20mm vs Porcelain, Seal Before Grouting

Terrazzo tiles come in two very different products that look alike in a showroom photo: real terrazzo, a cast slab of marble, quartz or glass chips set in cement or resin, and terrazzo-effect porcelain, a printed tile that copies the look. They are fixed, sealed, cleaned and priced differently, and choosing the wrong one for the wrong wall or floor is the most common terrazzo mistake we see. This page covers how to tell them apart, which one suits which room, and how real terrazzo has to be laid so it does not stain, crack or drag a wall down.

Real terrazzo or terrazzo-effect porcelain?

Terrazzo started in Venice as a way of using offcuts of marble: chips were set into a binder, then ground flat and polished so the aggregate showed through. Today you can buy it three ways.

Poured in situ. Laid wet across the whole floor, then machine-ground and polished. Seamless, beautiful, and a specialist trade. Homebuilding puts professionally installed poured terrazzo at £250 to £300 or more per square metre.
Precast terrazzo tiles. The real material, cut into tiles or slabs and fixed like stone. The same source puts real terrazzo tiles at £100 per square metre and up, before fitting.
Terrazzo-effect porcelain. A porcelain tile with the chip pattern printed into the glaze. It is waterproof, needs no sealing and costs a fraction of the real thing.

Precast terrazzo also splits into two binders. Cement-based terrazzo suits floors and outdoor use and is porous, so it has to be sealed. Resin-based terrazzo is denser and less porous, which is why it is preferred for worktops and splashbacks.

The quick way to tell real from printed in a showroom: turn the tile over and look at the edge. Real terrazzo shows the chips running right through the body. Porcelain shows a uniform clay body with the pattern only on the face. The second check is the pattern itself. A printed tile has a limited number of faces, so lay six or eight out on the floor and look for the same cluster of chips repeating.

Which one for which room

Bathroom walls and showers: porcelain, almost always. It is light, does not need sealing and copes with constant water. If you want real terrazzo in a shower, use a resin product and follow the maker’s sealing advice to the letter.
Kitchen floors and hallways: either works. Real terrazzo is harder-wearing in the sense that a chip shows the same material underneath, but it needs resealing. Porcelain is the low-maintenance choice for a busy family hallway.
Feature floors in living spaces: this is where real terrazzo earns its price. The depth of the polished aggregate is something print does not quite reproduce close up.

Thickness and weight: check the wall before you buy

Real terrazzo is heavy, and the weight decides where it can go. UK supplier Terrazzo Tiles recommends a minimum of 20 mm thick for floor tiles up to 600 x 600 mm, and 30 mm for larger formats up to 1200 mm. A fixing guide from Dutch supplier De Tegel puts a single 600 x 600 x 20 mm tile at about 20 kg. That works out at roughly 55 kg per square metre before any adhesive.

Close-up of a terrazzo step edge showing red and white marble chips through the full depth — The edge of a terrazzo step at a Miami Beach hotel: the aggregate runs through the body, which is how to tell real terrazzo from printed porcelain. | Miami Beach – Terrazzo, Hotel Pierre by P. Hughes (CC BY 4.0), via Wikimedia Commons, https://commons.wikimedia.org/wiki/File:Miami_Beach_-_Terrazzo,_Hotel_Pierre.jpg

The same supplier lists the maximum tile weights the common wall backgrounds will carry:

Gypsum plaster: 20 kg per square metre
Gypsum plasterboard: 32 kg per square metre
XPS insulated tile backer boards: 120 kg per square metre
Cement boards: 200 kg per square metre

Adhesive adds about 3 kg per square metre. So a 20 mm terrazzo floor tile cannot go on a plastered or plasterboard wall at all. Thinner 10 mm terrazzo wall tiles come to roughly 28 kg per square metre on the same maths, around 31 kg with adhesive, which is right at the plasterboard limit with nothing to spare. For any real terrazzo on a wall, we fix to cement board or a heavy-duty backer board. Our page on tile backer board vs plasterboard explains the swap.

Porcelain has none of this problem. Most terrazzo-effect wall tiles are under 10 mm thick and sit comfortably on plasterboard.

Floors need the same thought. On a suspended timber floor, a heavy stone-like tile needs a stiff, overboarded deck, because any bounce will crack the grout first and the tiles next. On concrete, check it is flat and dry, and use levelling compound before tiling rather than trying to pack the adhesive bed out.

How to lay real terrazzo tiles

Terrazzo is fixed more like natural stone than like ceramic. The sequence matters because the face is porous until it is sealed.

1. Adhesive and bed

Use a flexible cement-based adhesive. For pale terrazzo, use a white adhesive: grey adhesive can show through or shadow lighter tiles. Spread with a 10 to 12 mm notched trowel and back-butter each tile so there is a solid bed with no voids. Wipe dust off the back of each tile with a damp sponge first so the adhesive bonds. Our page on applying tile adhesive covers solid-bed technique.

2. Joints and levelling

Real terrazzo is made to tight tolerances and usually laid with 2 to 3 mm joints. With joints that narrow, any lip between tiles shows, so a tile levelling system is worth using on large formats.

3. Cutting

Cut with a water-cooled saw. A manual tile cutter will not score a 20 mm cast slab cleanly. Slightly damaged tiles from the delivery can usually be kept for cuts, so set them aside rather than sending them back.

4. Seal before you grout

This is the step that ruins most DIY terrazzo floors when it is skipped. Once the adhesive has cured and the face is clean and completely dry, apply a coat of impregnating sealer. It acts as a grout release, so the grout cannot soak into the porous face and leave a haze or stain. Allow it 12 to 24 hours to dry. Terrazzo Tiles recommends Lithofin Stainstop MN, two coats, one before and one after grouting.

5. Grout

Use a fine, unsanded grout in white or grey. Strong colours can stain the face. Work small areas, clean off as you go and do not let grout dry on the surface.

6. Seal again

When the floor is clean and fully dry, apply the second coat of sealer over tiles and joints. De Tegel’s guide advises waiting at least two weeks before giving the floor a thorough clean.

For the general method behind steps 4 and 6, see our page on sealing natural stone before grouting; terrazzo behaves the same way.

Underfloor heating, slip and outdoor use

Both real terrazzo and porcelain conduct heat well and work over underfloor heating. With cement terrazzo, the supplier advice is a flexible adhesive with an uncoupling mat such as Schlüter DITRA between the heated screed and the tiles, to absorb movement as the floor warms and cools. Our tiling over underfloor heating page covers commissioning the system before you tile.

On slip, sealed cement terrazzo from Terrazzo Tiles is quoted at a wet pendulum test value (PTV) of 42. A PTV of 36 or more is the level generally treated as low slip potential, so a sealed, honed finish is fine for most kitchens. A highly polished finish is a different matter in a wet area; ask for the PTV of the exact finish you are buying. Terrazzo-effect porcelain varies by range, so check the rating for that tile, especially for a shower floor or entrance.

Cement terrazzo can go outside if it is properly sealed and maintained, but frost and the British wet season are hard on any sealed porous surface. For a patio, a 20 mm terrazzo-effect porcelain paver is far less work; see laying outdoor porcelain paving.

Cleaning and resealing

Clean real terrazzo with warm water or a pH-neutral cleaner. Keep acids off it entirely: vinegar, lemon, limescale removers and many bathroom sprays etch the cement binder and dull the polish, and a sealer will not stop that. In a bathroom, this is the biggest practical argument for porcelain.

Plan to reseal real cement terrazzo every 12 to 18 months in a busy room. A simple test: drip water on the floor in a high-traffic spot. If it beads, the seal is working; if it darkens the tile within a few minutes, it is time to reseal. Resin terrazzo and porcelain need neither.

Ordering: batches, shade and waste

Real terrazzo is a cast product with natural aggregate, so shade varies between production batches. Order the whole job in one go, check the batch numbers on every box match, and order 10% extra for cuts and breakages. Open several boxes and mix tiles from each as you lay, so any variation spreads across the floor instead of forming a visible band.

Check the delivery before work starts. A 20 mm tile with a chipped corner may be fine for a cut, but a cracked one is not, and suppliers will deal with damage far more readily before anything is fixed.

Frequently asked questions

Are terrazzo tiles expensive?

Real terrazzo tiles start at around £100 per square metre for the tile alone, and poured terrazzo runs to £250 to £300 or more per square metre installed. Terrazzo-effect porcelain costs much less, and fitting is cheaper too because it needs no sealing and is lighter to handle.

Do terrazzo tiles need sealing?

Cement-based terrazzo does: once before grouting and once after, then every 12 to 18 months in busy areas. Resin terrazzo is far less porous. Terrazzo-effect porcelain needs no sealing at all.

Can you put terrazzo tiles on plasterboard?

Not 20 mm real terrazzo: at around 55 kg per square metre it is well over plasterboard’s 32 kg limit. Thin 10 mm terrazzo is right at the limit, so we would still use cement board. Porcelain terrazzo-effect tiles are fine on plasterboard.

Are terrazzo tiles slippery?

Sealed, honed cement terrazzo has been tested at a wet PTV of 42, which is low slip potential. Polished finishes are more slippery when wet, so check the PTV for the exact finish before using it in a bathroom.

Can terrazzo tiles go over underfloor heating?

Yes. Use a flexible adhesive, and with real terrazzo an uncoupling mat between the heated screed and the tile. Commission and run the heating before tiling so the screed has finished moving.

What should I not clean terrazzo with?

Anything acidic: vinegar, lemon, limescale removers and descaling bathroom sprays. Use warm water or a pH-neutral cleaner.

If you are planning a terrazzo floor or bathroom in Bromley or south east London, Bromley Tilers can advise on the substrate and fix it properly the first time.

020 8058 5574

contact@bromleytilers.co.uk