How to Install Mosaic Tile

Installing mosaic tile
LJM Photo/Getty Images

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 preattached tiles that are remarkably easy to install. In many ways, working with modern mosaics offer some advantages to working with standard ceramic or porcelain tile.

The Composition of 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.

Mosaic sheets can be composed of tiles of the same color, or they can use tiles of varying colors and different shapes for design effects. Most mosaic sheets are traditional ceramic tile, but there are also mosaics that use porcelain tile, glass tile, natural stone, or even unglazed terra cotta tiles. Mosaic sheets are usually made with small square tiles, but some mosaics consist of sheets of small rectangular tiles or other geometric shapes. They may even mix shapes within the same sheet. There are also narrow sheets of mosaic tiles that are used for borders and for other accent applications.

Preparation

Surface preparation for a mosaic tile installation is exactly the same as for standard ceramic tile. Surfaces must be perfectly flat and smooth. In modern tile work, the underlayment for mosaic tile 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.

As with any tile job, a good installation with mosaic tile requires a well-planned layout to ensure that grout seams run perfectly square. Professionals are very careful when planning layouts to minimize the amount of tile cutting necessary. Drawing precise layout lines will ensure a good installation.

Tools and Supplies You Will Need

The supplies required for installing mosaic tiles are the same used for any ceramic tile installation.

  • Tape measure
  • Framing square
  • Pencil
  • Mosaic tile sheets
  • Thinset adhesive
  • Notched trowel
  • Utility knife
  • Tile nippers or wet saw
  • Rubber mallet
  • Grout (unsanded or sanded, as required)
  • Mixing bucket
  • Grout float
  • Clean rags
  • Grout haze remover
  • Grout sealer
  • Paintbrush or roller

Instructions

Techniques for installing mosaic tile sheets are nearly identical to those for standard ceramic tile, but cutting can sometimes be easier since fitting partial sheets can be as simple as snipping the fiberglass backing to create custom-shaped sheets.

Mark Layout Lines

As with any tile installation, installing mosaic tiles begins with marking perpendicular layout lines on the surface to be tiled. This provides a cross-shaped grid at the center of the surface, where you will start the installation and move outward in all directions. Most pros begin 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.

Test-fitting tiles before you begin may help you adjust the layout to minimize the amount of cutting necessary.

Begin Installation at the Center

  1. Beginning at the center where the layout lines cross, use a notched trowel to apply a layer or thin-set adhesive to one of the layout quadrants, working in sections about 2 to 3 feet square. Your tile and the thin-set product will specify what size of a notched trowel to use. Some trowels use V-shaped notches, while others have square notches. Make sure not to overapply thin-set; you should be able to see the underlayment at the bottom of the grooves.
  2. Apply one sheet of mosaic tile into the corner of the 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.
  3. Install adjoining mosaic sheets 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.
  4. Once the first quadrant area is tiled, apply thin-set and install tiles in the remaining three quadrants.
  5. Work outward from the center until all full sheets of tile are installed.

"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).

Cutting Tile Sheets to Fit

As you approach the edges of the tile area, you will likely need to cut mosaic 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.

Cutting 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 nibbler, which looks like a pair of modified pliers and can be used to "nibble" each individual tile square within the sheet.

Finally, a rail cutter (or snap tile cutter, as it is sometimes called) can 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.

Install Cut Sheets of Tile

After cutting down full sheets of tile to the size you need, apply them to the layout in the same manner as full-sized sheets—applying thin-set adhesive and pressing the tiles into the adhesive. Use a scrap of plywood and a rubber mallet to "set" these tiles, as well.

Install 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 slightly before moving on to grouting.

Grout the Tile

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. Load the edge of a rubber grout float with grout, then spread the grout over the top of the tile.
  2. 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.
  3. Continue until all joints are filled with grout. This can be a lengthy process with mosaic tiles since there are many grout joints.
  4. Use the edge of the grout float to scrape off large amounts of excess grout from the face of the tiles.
  5. 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.
  6. 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

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 with 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.