A ceramic tile installation made with sheets of mosaic tile offers a great way to add visual interest to a room. Whether they are used on floors, walls, countertops, or backsplashes—and whether made from traditional ceramic tiles, porcelain, or glass tiles—mosaics create an intricate design effect that lends a look of luxury in any room.
Historically, mosaics were first painstakingly applied as individual tiny tiles to create a unified large surface with intricate patterns, but modern mosaics consist of convenient sheets of pre-attached tiles that are remarkably easy to install. With very small tiles or tiles with geometric shapes, mosaic sheets offer advantages over working with individual ceramic or porcelain tiles.
What Are Mosaic Tiles?
Modern mosaic tile is a product in which smaller ceramic tile squares—generally 2 inches square or smaller—are glued onto sheets of mesh fiberglass. The tiles are spaced on the sheets so the gaps between tiles are precisely the proper width for grout seams. This makes mosaic tile much quicker to install than using individual small tiles.
Equipment / Tools
- Tape measure
- Framing square
- Utility knife
- Screw gun
- Taping knife
- Chalk line
- Rubber mallet
- Tile nipper or wet saw
- Clean rags
- Paintbrush or roller
- Cement board
- Cement board screws
- Fiberglass cement board tape
- Thin-set adhesive
- Mosaic tile sheets
- Notched trowel
- Scrap of 2×4
- Grout (unsanded or sanded, as required)
- Grout haze remover
- Grout sealer
- Latex adhesive (if needed)
Prepare the Surface
As with any tile installation, the surface for mosaic tile must be perfectly flat and smooth. In modern tile work, the underlayment is generally cement board applied over a plywood subfloor or directly against wall studs. Mosaic tile can be laid directly on plywood or wallboard (in non-wet locations), but cement board offers the best underlayment and is the preferred choice for professionals.
Start by installing full sheets of cement board, then cut pieces to fit the remaining spaces. Cement board is best cut by scoring it with a sharp utility knife, guided by square, then snapping it along the score lines. Use cement board screws to secure the panels to the studs, with the rough side of the panels facing out. Leave a gap of about 1/8 inch between panels.
Cover the seams between cement board panels with 2-inch wide fiberglass cement board tape, then cover the tape with a thin layer of thin-set adhesive, applied with a taping knife
Plan the Tile Layout
A good installation with mosaic tile requires a well-planned layout to ensure that grout seams run perfectly square. Draw intersecting perpendicular layout lines that bisect the surface top to bottom and left to right. Most pros begin installation at the very center of the surface, first installing all full sheets of tile, then doing whatever cutting is necessary at the borders and around obstacles.
Attach the First Tile Sheet
Beginning at the center where the layout lines cross, use a notched trowel to apply a layer of thin-set adhesive to one of the layout quadrants, working in sections about 2 to 3 feet square. Make sure not to over-apply the adhesive; you should be able to see the cement board at the bottom of the grooves.
Apply the first tile sheet into the corner of the first quadrant, carefully adjusting it with your hands to ensure that it is perfectly square with the layout lines. Press firmly to embed the tile in the thin-set. Hold for several seconds, and watch for any sliding as you release hand pressure on the tile
Fill in the First Quadrant
Install adjoining mosaic sheets in the first quadrant in the same manner, using tile spacers to ensure that gaps between sheets are exactly the same as the gaps between tiles within the sheets. With mosaic sheets, the small tiles are staggered so the sheets interlock. Be careful to ensure that the grout seams remain uniform throughout the tile field.
“Set” the Tiles
Mosaic sheets do not behave in quite the same way as single large tiles; they can ripple or form waves on the surface. To prevent this, after every few sheets are installed, “set” the tiles by using a small piece of plywood (about 8 inches square) and a rubber mallet to tap down the mosaic sheet into the thin-set. This flattens the tile area, giving it a nice smooth surface. Pay particular attention to the seams between sheets, to make sure there is no lippage (where one row of tiles is higher than its neighboring row) or slippage (where gaps between sheets are wider than the grout gaps within the sheets).
Cut the Tile Sheets to Fit
As you approach the edges of the tile area, you will likely need to cut tile sheets down to size. In some cases, simply cutting the fiberglass mesh will create a partial sheet exactly the right size for your needs, but in other situations, you may need to trim the individual edge tiles to fit precisely. Avoid this when you can; you may be able to use cove tiles or other accents, or baseboard moldings, to cover the gaps at the edge of a layout. To cut the sheets down to size, simply cut the mesh backing along the grout seams using a sharp utility knife.
Install the cut sheets of tile in the same fashion as the full sheets.
Cut the Individual Tiles
Where individual tiles within the sheet need to be cut, you have several options. Sheets of tile can be fed through a tile wet saw in the same manner as used with full-size ceramic tiles. This is by far the easiest way to cut tiles, and it is the best strategy for very large tile installations where lots of cutting is needed. Wet saws are available for rental at home improvement centers and tool leasing outlets. Simple wet saws are relatively inexpensive and are a good investment if you do regular tile work.
Another option is a simple hand tool known as a tile nipper, which looks like a pair of modified pliers and can be used to “nibble” each individual tile square within the sheet. Or, you can use a rail cutter (or snap tile cutter, as it is sometimes called) to score an entire row of tiles. The tool’s pivot lever can then be used to snap each individual tile within the sheet, one at a time
Complete Installation on the Remaining Quadrants
With one quadrant of the tile job done, repeat the preceding steps to complete the other three quadrants, one at a time. With each quadrant, work from the center point of the layout outward to the edges.
Install the Trim Tiles
Conclude the installation by installing whatever trim or accent tiles you are using. This can include bullnose edging, cove tiles, or baseboard tiles. These are also applied using thin-set adhesive. After all the tiles are installed, allow the installation to harden a bit before moving on to grouting.
Mix the Grout
After the mosaic tiles have thoroughly hardened into the thin-set and are in no danger of shifting, mix up a batch of grout from dry power (or you can use pre-mixed grout for small jobs). Generally, use unsanded grout for tiles with grout seams 1/8 inch or smaller, and sanded grout where the seams are wider.1 Follow the manufacturer’s directions for mixing.
Apply the Grout
Load the edge of a rubber grout float with grout, then spread the grout over the top of the tile. Using multiple passes of the grout float, force the grout into the joints, holding the float at a 45-degree angle to the surface. The edge of the float is what forces the grout deep into the joints. You will need to alternate the direction of the grout float to ensure that grout fully fills all joints.
Continue until all joints are filled with grout. With mosaic tiles, this can be a lengthy process since there are many grout joints. Use the edge of the grout float to scrape off large amounts of excess grout from the face of the tiles.
Clean the Tile Surface
Allow the grout to harden slightly, according to the manufacturer’s directions, then wipe the face of the tiles with a clean cloth to remove dried grout.
After the grout is fully cured (again, according to the manufacturer’s direction), use a liquid grout haze remover to get rid of any remaining grout film.
Seal the Grout Lines
Because tile grout is porous, it must be sealed in order to protect the underlayment, as well as the integrity of the grout. This is particularly important in damp locations, such as showers. Use whatever type of sealer is recommended by the grout manufacturer, and wait until the grout is completely dry and cured before applying it.
With mosaic tiles and their many grout lines, the easiest way to apply sealer is by brushing or rolling the entire surface. As the surface begins to dry, wipe away excess sealer from the surface of the tiles; it will have already penetrated the grout. Most sealers suggest two applications for initial sealing, then additional application every one to two years.