Q: I want to do a large mosaic tile floor in my new room addition. I have no clue where to start. I’ve never done tile work before, and I don’t want to goof up and have to rip it up. What can you share to ensure success? There will be some heavy furniture on the floor. Is that an issue?

A: Who doesn’t love an eye-popping, drop-dead-gorgeous mosaic tile floor? It’s possible for a beginner to lay a mosaic tile floor as a DIY project, but you need to start with baby steps. I’ve seen some mosaic tile installations that make my eyes hurt because they were poorly planned or the installer/artist rushed the job.

Let’s unpack the project by splitting it into two parts, starting with the artistic aspect.

I’m not an artist, but I know enough to realize that a mosaic tile scene can either be abstract or represent something you or another person would recognize. For example, you might be trying to create a mosaic of the mountain scene at sunrise that you see from a window. It could be a mosaic of a flower or a pet. There are countless things you might try to recreate using small, colored pieces of tile.

If you’ve never done this before, you should start small. I recommend creating a mosaic that measures about 2 feet by 4 feet. That gives you enough real estate to create something that will have a visual impact, but not require an overwhelming amount of work.

Start with a scale drawing of the design that you want to create, with all the correct colors and shading. Don’t try to recreate the Last Supper on your first try — stick with something simple.


Using your color drawing as your North Star, gather pieces of tile that are all the same thickness and begin to cut and snip them to the sizes that you’ll need. 

Beware of using porcelain tile on your starter project; porcelain is an extremely hard material that’s difficult to snip and shape. Instead, use a softer tile with a traditional clay core, which will snap with ease. Use tile nippers for the thinnest pieces. 

If you’re a digital-minded person, think of each tile piece as a pixel within an image on your computer or smartphone. You can use online how-to video or
Instagram accounts that feature photos of finished mosaic tile pieces to grasp what you need to do.

Lay the cut pieces of tile next to one another on the floor, making sure you allow for a grout line that might be as narrow as 1/8-inch around each piece of tile.

Once you have your mosaic design created and you’re happy with how it looks from 5-10 feet away, you’re ready to install the tile and grout it.

Floor tiles must be installed in thinset, which is a mix of fine silica sand and Portland cement. Thinset allows the mosaic tile to bond well to a solid subfloor. Once the thinset is cured, it’s almost as hard as a rock, and it doesn’t move. Organic tile mastic — which is thick like icing on a cake — should never be used to set floor tile. It can move and the tile can crack.


A secret to good installation is to match the size of the tile to the trowel that will be used to put down the thinset. If your mosaic tile is about the size of a postage stamp, or about 1 inch by 1 inch, then you need to use the smallest notched trowel you can find. A 1/8-inch-by-1/8-inch, square-notched trowel would be my recommendation.

Hold the trowel at a 30- to 45-degree angle as you spread the thinset onto a piece of cement board that has been dampened with water. Only put down as much thinset as you can cover with tile in 5 minutes or less. You should work quickly, especially if you live in a dry climate where the thinset can skin over rapidly. If this happens, the bond will be poor between the thinset and the pieces of tile.

Avoid allowing any thinset to ooze up between the pieces of tile. Remove any excess immediately, making sure you don’t smear it on the face of the tile. 

The top of each tile must be in the same plane, so place a small piece of smooth, flat plywood on the tiles and lightly tap it so the tops of the tiles are all level. Use sanded grout between the tiles to finish the job.

Tim Carter has worked as a home-improvement professional for more than 30 years. To submit a question or to learn more, visit AsktheBuilder.com.