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Mosaic tile work requires patience, skill

Q: I visited a home that had an interesting mosaic pattern inset into regular floor tile. I loved how it broke up the monotony of the tile. How can I install ceramic floor tile in this manner? I looked closely and the mosaic floor tiles were identical. I assume these came fabricated. Any tips you can share would be appreciated.

A: I've installed many ceramic tile floors in my career. Not only have I seen what you're talking about, I have installed mosaic patterns. It's not hard to do; it just takes time, patience and skill.

The first thing you need to do is to check the thickness of the ceramic and mosaic tiles. If they don't match in thickness, you may have a nightmare on your hands, or at least some extra work. In that event, you want the mosaic tiles to be thinner than the field tiles. (The field tiles are the plain ones that cover the majority of the floor area.)

If the mosaic tiles are thinner than the field tile, all you have to do is put more thinset adhesive under the mosaic than under the field tile. Can you imagine how hard it would be to do the opposite? Trying to build up the field tiles would result in a mess and an uneven floor surface. When setting the thinner mosaic tile, use a straightedge to make sure the top surface of the mosaic tile is in the same plane as the field tile. All of this hassle is avoided if you can work with tiles that are the same thickness.

The mosaic patterns you mentioned almost always come glued together in a sheet. A thin fiberglass mat holds them together, allowing you to place the complete pattern on top of the full field tiles. Doing this allows you to trace the outline of the entire mosaic pattern onto the field tile.

Temporarily tape the mosaic pattern on top of field tiles that are set onto the floor with the proper grout spacing. Use a fine-tipped permanent marker to trace the outline of the mosaic pattern onto the field tile. Be sure the line you trace is away from the edge of the mosaic tiles the same width as the grout lines between field tile.

The resulting traced line will be irregular, meaning you need to use any of a number of tools to cut the curved, angled or irregular line. A diamond wet saw, an angle grinder with an abrasive wheel, a hand nipping tool, even a crude carbide rod saw will all work. Your patience and skill will determine the final look. Cut along the line.

For professional results there are several things you can do. The floor should be as solid as possible, with no spring to it. Especially in homes without a concrete slab, use a decoupling membrane so the tile can move independently of the floor. These plastic membranes look like the bottom of a waffle iron. It's worth it if you want the floor to be crack-free.

Be sure you try to get the floor in the same plane. This doesn't mean the floor has to be level. To be in the same plane means no humps, no bumps and no gaps under a long straightedge when placed on the floor. Use self-leveling compound to help get the floor smooth.

Use a notched trowel appropriate to the tile you're using. The tile manufacturer will often publish what the minimum notch size should be. The larger the notch, the more thinset adhesive you use. Usually the notch size gets bigger as the tile size increases.

Tim Carter is a licensed contractor. To view previous columns or tap into his archive of information, go to You can write to Tim Carter at P.O. Box 36352, Cincinnati, OH 45236-0352.


Use an adhesive that fits the job

Do not use organic mastic to install floor tile. Organic mastic is a creamy adhesive that looks like cake icing. This adhesive works for wall tile but not for floors. It will flex slightly when you apply concentrated pressure on a tile. If the adhesive moves, it will cause the tile to crack.

Thinset adhesive is like brick mortar. When it cures after 24 to 48 hours, it will not flex. When applying thinset, be sure the surface you're covering is dust-free. Only mix as much thinset as you can apply and cover with tile in an hour or less. Never add more water to thinset that's starting to harden. This will weaken it and may cause the tile to pop off later.

Mosaic tile work requires patience, skill 01/01/10 [Last modified: Friday, January 1, 2010 3:30am]
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