Mosaic Tile Sheet Installation is Hard. Here's How to Do It.

Installing Mosaic Tile
Installing Mosaic Tile. LJM Photo / Getty Images

Who Said This Was Easy?

Large-tile installation (12" square or greater) looks simple once you get into the world of mosaic tile sheets.

These 1 inch or smaller square tiles (called tesserae, plural) can, surprisingly, make installation quite difficult. In the past, tile installers painstakingly laid each tessera individually. Today, these tiles come attached in fiberglass mesh-bound sheets of 144 at a time.

Easy?  Not so much.

Avoid Warps, Waves, and Lips

Unified bundles of mosaic tessarae do not behave the way a single 12" x 12" tile might.  

They still can warp, wave, shift, and create lippage, making your new tile floor look like an ancient Roman floor, and not in a good way.

Warps and waves are horizontal imperfections that look like subtle ocean waves prior to cresting.  Shifts are grout width variations within tile sheets.  And lippage is a potentially hazardous feature where one row of tiles is higher than its neighboring row.  Lips are trip hazards.

The following tricks will make installation go easier and your end product more attractive:

1.  Avoid Cutting Tiles If Possible

Tile installation is as much about cutting as it is about laying.  However, make every effort to avoid cutting 1" mosaic tiles.  

If you come to an edge and anticipate cutting a long line of mosaic tiles, first see if the baseboard or trim will cover full sized tiles rather than proceeding to another row of cut tiles.

2.  This Is How You Cut Tiles If You Must Cut Tiles

You have several options for tile-cutting, ranging from cheap to very expensive.  As a DIYer, you will not be cutting much mosaic, in which can you can use a rail cutter and a tile nibbler.

The rail cutter (or snap tile cutter, as it is sometimes called) can cut an entire row of tiles by scoring them and then snapping them in half.

The nibbler looks like a pair of pliers and it allows you to cut one tile at a time.

3.  Cut the Mesh Between Tiles

The way to cut mosaic tile sheets is to leave individual tiles whole and to cut the fiberglass mess between the tiles.

4.  Best Way:  Cut From Back

If you need to cut a mosaic sheet, the best way to do this is to cut from the back with a utility knife.  The fiberglass mesh will easily yield to a sharp utility knife.

5.  Second Best:  On Top, With Scissors

If you must cut the mosaic sheet from the top with scissors, it is harder to get a clean cut. You will need to slightly bend the two courses of tiles between which you are cutting. This gives your scissors room to fit.

6.  Be Careful of Shifting Tiles

Even though the tiles are affixed to a single sheet, the sheets are flexible and do not keep the tiles within perfectly square.

After you embed the mosaic tile sheet in the thinset mortar, make sure that the tiles within the sheet are properly lined up.

7.  Do Not Use Too Much Thinset

After you have laid down the proper amount of thinset, you press down the mosaic and thinset mushes up between the tiles.

Thinset mush matters less when you are working with big, single tiles (12"x12", for instance), because you only have four edges to clean.

But when there are 144 tiles in a mosaic, cleaning out the seams can be difficult and it rarely looks good.

Use only as much thinset as your v- or square-notched trowel dispenses, no more.

8.  Gently Tamp the Mosaic Into Thinset

Use a small piece of plywood (about 8 inches square) and a rubber mallet to tap down the mosaic sheet into the thinset mortar.

This flattens the tile area, giving it a nice smooth surface. Also, it ensures that the mosaic tile sheet is firmly embedded in the mortar.