To make a tile mosaic, you stick tesserae of ceramic, zellige, pigmented cement or glass onto a rigid base, then fill the joints with grout and clean off the excess before it hardens. A small panel can be finished in a weekend: one afternoon to design and cut, another to stick the pieces down, 24 hours of drying and a morning to grout and seal.
What is a tile mosaic and how is it different from conventional tiling?
A mosaic is a composition of small pieces, the tesserae, which only make sense as a whole: the design comes from the way they are combined and from the joint that separates them. In conventional tiling, the unit is the tile, decorative in its own right and laid in regular rows.
The technique is more than two thousand years old: the Romans set tesserae of stone and glass in a bed of mortar (opus tessellatum), and the mosaics found at Zeugma (Turkey) still preserve the faces of the nine Muses almost intact. Today the bed is a cement-based adhesive.
In the trade, “ceramic mosaic” also refers to a specific product: factory-made tesserae glued to a mesh, in sheets that are laid like one large tile. This guide covers handmade mosaic, following the practice of our workshop in Seville.
What types of mosaic are there: ceramic, zellige, cement tile or trencadís?
They are classified by the material of the tesserae. In practice, the material changes how each piece is cut, how much it weighs and how much water it absorbs: that is what determines the adhesive, the grout and the sealing.
| Type of mosaic | Material | Typical piece | Where it is used | DIY difficulty |
|---|---|---|---|---|
| Mesh-mounted ceramic | Stoneware or porcelain on mesh | 1 to 5 cm, in 30 × 30 cm sheets | Bathrooms, kitchens, swimming pools | Low |
| Zellige | Glazed clay cut by hand | 10 × 10 and 5 × 5 cm; Chakar, Darj, Kora | Walls, kitchens, stairs, fountains | Medium (irregular pieces) |
| Cement tile | Pressed pigmented cement, unfired | 20 × 20, 10 × 10 and the 7 × 7 cm insert | Indoor floors, cement tile rugs | Medium to high (weight and sealing) |
| Trencadís | Fragments of tile or crockery | Pieces of 2 to 4 cm | Tables, plant pots, benches, murals | Low |
| Vitreous glass | Glass paste, almost zero absorption | 2 × 2 and 2.5 × 2.5 cm on mesh | Swimming pools, showers | Low to medium |
| Stone | Marble or natural stone | 1 to 3 cm | Floors, murals | High |
Water absorption is the deciding factor. In our laboratory tests, 10 × 10 cm glazed zellige absorbs 15.7% and terracotta 16.9% (UNE-EN ISO 10545-3, the Spanish edition of EN ISO 10545-3), compared with 5.9–6.2% for hydraulic terrazzo (UNE-EN 13748-1); porcelain stoneware stays below 0.5%. The more porous the piece, the more important it is to apply a water-repellent before grouting.
What materials and tools do you need to make a mosaic?
For one square metre: the pieces plus 10% for wastage, 2 to 7 kg of adhesive and 0.5 to 2 kg of grout, depending on the joint. The exact coverage is given on the bag.
- Pieces: zellige, whole or broken tiles, cement tiles or glass tesserae, 10% more than calculated (15% for diagonal layouts): the shade varies from batch to batch.
- Substrate: moisture-resistant board 10 mm thick or more for panels and furniture; a rendered wall or cement board; a screeded floor, level and dry.
- Adhesive: C2 cement-based tile adhesive (EN 12004) on walls and floors; for zellige, a flexible one such as Elasticer by Fixcer; on boards for indoor use, a D2 dispersion adhesive over a primer.
- Grout: fine-grained, light-coloured CG2 cement-based grout (EN 13888); epoxy (RG) in showers and on worktops. With cement tiles, never tinted.
- Water-repellent: essential for cement tiles, terracotta and zellige. In our installation guide we recommend an anti-stain water- and oil-repellent with a natural finish, such as FOB Xtreme by FILA.
- Cutting and protection: a hammer and a cloth, mosaic nippers, a manual tile cutter for ceramics, a water-cooled diamond blade for zellige and cement tiles; safety glasses, gloves and a dust mask.
- Laying: a 3–4 mm notched trowel, a rubber grout float, a spatula, a sponge, a spirit level, a straightedge and profiles or battens for the frame.
How many pieces fit into a square metre depends on the format; the weight per m² follows from the weight of each piece:
| Piece (reference) | Dimensions | Pieces per m² | Weight per piece | Approx. weight per m² |
|---|---|---|---|---|
| Zellige Mjeddij ZS03 | 5 × 5 × 1 cm | 400 | 0.05 kg | 20 kg |
| Zellige Mjeddij ZS02 | 10 × 10 × 1 cm | 100 | 0.16 kg | 16 kg |
| Zellige Bejemat ZS15 | 15 × 5 × 1.5 cm | 134 | 0.18 kg | 24 kg |
| Zellige sheet ZP051 Khatim-kmar | 28 × 28 cm | 12.75 | 1.80 kg | 23 kg |
| Cement tile insert H07 | 7 × 7 × 1.5 cm | 205 | 0.25 kg | 51 kg |
| Cement tile H06 | 10 × 10 × 1.5 cm | 100 | 0.35 kg | 35 kg |
| Cement tile H03 | 20 × 20 × 1.5 cm | 25 | 1.30 kg | 33 kg |
How to make a tile mosaic in 7 steps
The order is always the same; what changes is the adhesive, the joint width and whether the pieces need protecting before grouting. Timings are for 1 m² done by hand.
- Design at full scale.
- Prepare the substrate.
- Cut or break up the pieces.
- Stick down area by area, keeping to the joint width.
- Leave to dry for 24 hours.
- Protect porous pieces, then grout.
- Clean and seal.
1. Design the mosaic and make the template
Draw the design at 1:1 scale on the substrate and decide on the joint width, which changes the number of pieces. Then do a dry layout: place the pieces without adhesive, make corrections, take a photo and number the areas.
Time: 1–3 hours. Common mistake: designing at a reduced scale and then finding that the pieces do not complete the design.
2. Prepare the substrate
On a board: sand it, apply a primer and fix a frame of aluminium profiles or battens around the perimeter, which holds the grout in and protects the edges. On a wall: dry, flat render with no loose paint. On a floor: a level, dry screed, never fresh mortar.
Time: 1 hour plus the drying time of the primer. Common mistake: standard MDF in a bathroom; it swells and lifts the mosaic.
3. Cut or break up the pieces
For trencadís, wrap the tile in a cloth and strike it with the hammer until you have pieces of 2 to 4 cm; the cloth stops splinters from flying. Trim the edges with the nippers and sort the pieces by colour. Straight cuts in ceramic tiles are made with a manual tile cutter; zellige and cement tiles are cut with a water-cooled diamond blade: if cut dry, the glaze chips, and a cement tile is never broken with a hammer.
Time: 2–4 hours per m² for trencadís. Common mistake: cutting without safety glasses or gloves.
4. Stick the pieces down
Spread the adhesive over areas of about 30 × 30 cm, small enough to cover before it skins over (open time of 20–30 minutes). With cement tiles, use back-buttering (double spreading) — adhesive on the substrate and on the back of the tile — and level each one by hand, without a hammer, as we explain in detail in our guide to laying cement tiles. With zellige, use a flexible adhesive and lay the pieces almost butt-jointed.
Usual joint widths: zellige 0 to 2 mm, cement tiles 1 to 2 mm, ceramic 2 to 3 mm and trencadís 2 to 5 mm. Remove any adhesive that squeezes up into the joints before it hardens.
Time: 1–2 hours per m²; twice as long for trencadís. Common mistake: using grab adhesive or silicone on pieces that will get wet.
5. Leave to dry
Wait at least 24 hours before grouting and do not walk on a mosaic floor for 24–48 hours. With cement tiles, once the adhesive is dry, wash them with plenty of water to remove the pigmented dust that covers them.
Time: 24–48 hours. Common mistake: grouting on the same day; the pieces shift and the grout cracks.
6. Protect the pieces and grout
On cement tiles and terracotta, apply the water- and oil-repellent before grouting: without that layer, the grout sticks to the pigments and will not come off. Fill the joints with a spatula, wipe off the excess immediately and never use tinted grout.
With zellige and ceramic tiles, spread the grout diagonally with a rubber float, without overloading the surface, so as not to clog the ripples in the glaze; when the joint turns matt (15–20 minutes), clean with a barely damp sponge. Test dark colours on a spare piece first. There is more detail in our guide to grout for zellige.
Time: 1 hour per m² plus 24 hours of curing. Common mistake: letting the grout dry on the pieces; the cement haze is hard to get off the glaze.
7. Clean and seal
The next day, wash with water and neutral soap; never with acids, bleach or ammonia, which attack pigmented cement and dull glazes. Once everything is dry, brush on a thin coat of water-repellent; on a board, varnish the edges and the back.
Time: 1 hour, then 48–72 hours out of use. Common mistake: sealing before the construction moisture has evaporated.
Can you make a tile mosaic on a wall?
Yes: walls are the most common place for zellige and trencadís. Compared with a floor, four things change: the adhesive, the weight the substrate can bear, setting out from the bottom up and waterproofing in wet areas.
- Adhesive: C2 TE S1 tile adhesive; the T stops the pieces from slipping, the E extends the open time and S1 allows for small movements.
- Weight: 10 × 10 cm zellige comes to around 16 kg/m² and cement tiles in the same format to 35 kg/m². Check the load the partition wall can take, especially if it is plasterboard.
- Setting-out: fix a level batten at the height of the first full row and work upwards from there; the row of cut pieces goes in last.
- Wet areas and outdoors: waterproof the substrate, use CG2 W or epoxy grout and seal zellige and terracotta, which absorb between 15% and 17% water; if there is a risk of frost, check with the workshop first.
What mistakes should you avoid when making a mosaic?
When a mosaic goes wrong, it is almost always for the same reasons: too few pieces, the wrong grout and rushing.
- Buying only the exact number of pieces and then making up the shortfall with another batch in a different shade.
- Grouting cement tiles or terracotta with tinted grout, or without applying a water-repellent first.
- Breaking up tiles without a cloth or safety glasses.
- Using grab adhesive in wet areas, or rigid tile adhesive on a board that flexes.
- Laying on fresh mortar or a damp substrate: salt deposits and efflorescence.
- Grouting on the same day, or cleaning off the cement haze with acids.
Zellige mosaic: the mosaic that comes ready-made
Zellige is the handmade mosaic you can buy ready-assembled. In Morocco, master craftsmen cut each tessera from a glazed tile with a mallet and a menqach, assemble the design face down on a template and fix the pieces together from the back into panels: the classic indirect method. We describe the process in our article on how zellige is made.
At Demosaica we work with it in two ways. With individual zellige pieces (Mjeddij in 10 × 10, 5 × 5 and 3 × 3 cm, rectangular Bejemat, Chakar, Darj, Fekroun or Kora) you compose your own mosaic: chequerboards, herringbone, borders or stars. With zellige sheets the motif arrives already assembled: the ZP051 Khatim-kmar measures 28 × 28 cm, weighs 1.80 kg and 12.75 of them cover one m². They are laid as in steps 4 to 7.
The cement tile is the other mosaic that comes ready-made; that is why in Spanish it is also called mosaico hidráulico, “hydraulic mosaic”. Each 20 × 20 cm tile carries the complete design: the colour is poured into a mould with dividers, covered with cement and pressed cold, without firing.
Frequently asked questions about how to make a tile mosaic
What adhesive is used for a tile mosaic?
On a masonry wall or floor, class C2 tile adhesive (EN 12004): on walls with the letter T, so that the pieces do not slip, and S1 if the substrate moves or the mosaic is zellige or cement tile. On boards for indoor use, a D2 dispersion adhesive over a primer. Grab adhesives are only suitable for objects that do not get wet.
Can you make a mosaic with broken tiles?
Yes: that is trencadís, a broken-tile mosaic. Wrap the tile in a cloth, strike it with the hammer until you have pieces of 2 to 4 cm and trim the edges with the nippers. Combine tiles of the same thickness so that the surface ends up flat, leave joints of 2 to 5 mm and grout with a light-coloured grout.
How much does a tile mosaic cost per m²?
It depends on three items: the pieces (trencadís made with leftover tiles costs next to nothing; handmade zellige and cement tiles are priced as craft products), the consumables (adhesive, grout and water-repellent) and the labour, which in a handmade mosaic is the largest share. Check prices, lead times and minimum orders with the workshop.
What grout is used for a mosaic?
An improved cement-based grout (CG2 under EN 13888), fine-grained for joints of 1 to 3 mm, in a light or neutral colour unless you are looking for contrast. In showers, on worktops and outdoors, an epoxy grout (RG) can be worthwhile: it is more waterproof but harder to apply. With cement tiles, never use tinted grout: it stains the colour irreversibly.
How do you seal a cement tile mosaic?
With a water- and oil-repellent brushed on in a thin coat over clean, dry tiles; in our installation guide we recommend an anti-stain product with a natural finish, such as FOB Xtreme by FILA. Ideally, treat the pieces before laying them or, at the very least, before grouting. If you do it at the end, wait until the construction moisture has evaporated.
What is a ceramic mosaic and how does it differ from zellige?
A ceramic mosaic is a covering made of small tesserae of stoneware, porcelain or glazed ceramic, 1 to 5 cm across, glued to a mesh in sheets of about 30 × 30 cm: industrial and uniform. Zellige is also glazed ceramic, but each tessera is cut by hand and no two are the same. Cement tile is not ceramic: it is pigmented cement pressed without firing.
If you would like to start with a mosaic that arrives ready-assembled, the zellige tile catalogue brings together individual pieces, sheets and borders. Ask the workshop for samples and check the colour in the light of your own space.
