Installing marble tile is similar to installing other types of tile, such as ceramic or porcelain. In fact, the steps are pretty straightforward. After preparing the subfloor, glue down the tiles, grout, then seal. If you've installed tile previously, then chances are you already own most of the tools needed to install marble tile.
Before Getting Started
The costs for genuine marble floor tiles can vary tremendously depending on the color and style of tile. Some marble is relatively inexpensive, costing only about $4 to $5 per square foot, but it's also possible to spend $75 or even more per square foot if you choose very unusual marble from an exotic location. But the standard marble tiles available at big box home improvement centers typically costs between $5 and $20 per square foot.
Natural stone such as marble is a more difficult tile to cut, requiring a power wet saw, which can be rented at relatively low daily or weekly rates. But wet saws are not terribly expensive, and you might well want to invest in a saw of your own, especially if you expect to do more tile work.
Equipment / Tools
- 1/4-inch notched trowel
- Drill driver
- 6-inch drywall knife
- Tape measure
- Chalk line
- Tile spacers
- Rubber mallet
- Wet saw, if not using custom-cut tile pieces
- Diamond-tipped hole saws (if needed)
- Utility knife
- Foam brush
- Work gloves
- Grout float
- Grout sponge
- Marble tile
- Thinset mortar (tile adhesive)
- Cement board sheets
- 1 1/4-inch cement board screws
- Cement board joint tape
- Straight 2x4 board
- Marble tile-and-grout sealer
Prepare the Subfloor
Marble floor tile (like all floor tile) requires a smooth, flat, water-resistant base for installation. In most cases, this will require removing the existing floor covering down to the subfloor layer, which is usually plywood or MDF.
Once you have exposed the wood subfloor, cover it with a layer of cement board to add both stiffness and moisture resistance to the floor. Cement board doesn't stop moisture from passing through it—it's not a vapor or moisture barrier—but it won't be damaged by moisture the same way wood is. Cement board also is engineered to bond very well with thin-set mortar adhesive, which you will use to install your marble tile.
Create Reference Lines
Your installation will look best if the tiles radiate outward from the center of the room, rather than starting abruptly from one of the walls. In order to achieve this symmetrical effect, you need to create reference lines on the surface of the cement board underlayment.
Find the center of two opposing walls and use a chalk line to mark a path between them, dividing the room in half.
Then, measure to the center of that line, and use a T-square to draw a perpendicular line at the mark, using a pencil. Snap a chalk line across the floor using the pencil line as a guide, dividing the floor into four equal quadrants.
Check your layout by test-fitting full tiles along both reference lines from wall to wall. If the last row of tiles against any of the walls is less than a few inches wide, adjust your chalk line grid as needed so that the tiles along the walls are an acceptable width, based on your preference.
Mix and Spread the Mortar
Mix thin-set mortar according to the manufacturer's instructions. Mix only a little bit at a time, and make more when necessary. The thickness of the thin-set is critical and varies by the size of tiles and trowel notch used. The ratio of eater to dry mix should be maintained when mixing small amounts. A digital kitchen scale, measuring cup, and a little math will enable that ratio to be maintained at different amounts of mix.
Using a notched trowel, spread the adhesive onto the floor, starting where the reference lines intersect at the center of the room.
As you work, use the notched edge of the trowel to create grooves in the mortar. This will increase the adhesive strength of the bond between the cement board and the bottom of the marble. Ridges of mortar should always run in one direction. This allows air to escape for a uniform set.
Set the First Tile
Spread enough mortar to easily cover the bottom of a single tile, and make sure that its entire surface is notched. Gently press the first tile into place, aligning two of its edges with the chalk lines in the corner of the layout. As you press it down, twist the tile slightly to ensure that it properly sets in the mortar bed below.
"Set" the Tile With a Rubber Mallet
A rubber mallet is a large hammer with a soft rubber head. Use this to lightly tap the surface of the marble tile, pressing it more firmly into the mortar. However, be careful not to tap too hard, as marble is a relatively soft material and can crack rather easily. Avoid moving the tile as you are setting it.
Install Additional Tiles
Continue to spread mortar for each tile, then place the tile before moving on to the next one. Follow the reference line towards the wall, using it as a guide to keeping your placement straight. Use tile spacers to maintain consistent spacing between tiles. The spacers should be selected for whatever width you have chosen for the joints. Spacers help ensure the grout lines are sharp and uniform.
Install the Remaining Full-Size Tiles
After placing every three or four tiles, use a 2x4 board to ensure that they are at a uniform height. Place the board across the tiles, and tap the board lightly with the rubber mallet. If the marble is polished you may want to cover the front of the wood with a piece of carpet to prevent scratches. You can also do this across multiple rows when you have more tiles installed.
Once you reach the wall with the first row, take note of the gap at the end that may require a custom-cut piece. Then, move back to the center point of the reference lines, and continue to place tiles adjacent to the first row. Take a moment after every few tiles to ensure that all of your lines meet up and the entire floor looks sharp and consistent.
As you work, be careful not to step on any installed tiles. Typically, marble floor tile should be allowed to set for at least 48 hours after installation. Because of this, you have to be careful not to tile yourself into a corner that you can not escape from. Be sure to leave a traffic path for yourself; the last quadrant you work on should be the one where the door is located.
Cut Tiles With a Wet Saw
Use a wet tile saw to cut tiles as needed. You can buy a small wet saw for under $100, but many DIYers simply rent one by the day or week. Smaller, portable saws are able to handle basic straight cuts on tiles up to 12 inches. Rental charges may include a flat fee for the saw plus a prorated charge for wear on the diamond blade.
For difficult cuts, or if you prefer not to use a saw, ask your tile supplier if they will cut pieces for you.
If you need to cut holes in marble tile, such as may be necessary if you have plumbing pipes coming up through the floor, special hole saws with diamond-encrusted cutting edges can be used. The hole saws are simply mounted in a power drill. Make sure to cut at a slow speed to prevent overheating the hole saw.
Remove Excess Mortar
If there is any excess adhesive that has oozed up from the gaps between tiles, use a paint stick or utility knife to remove it.
When all tile has been installed, let the mortar adhesive dry completely, following the manufacturer's directions. Do not walk on the floor during this time, or you risk moving or depressing a tile.
Seal the Marble
Marble is porous, and many materials can penetrate the surface of the stone, causing permanent stains. For this reason, it must be sealed with a high-quality marble tile sealant before you grout. Grout can badly stain marble tile if it is applied before the marble is sealed.
If you have polished marble, apply a very thin coat of sealant. Use the foam brush to smooth out any puddles or tiny bubbles that appear on the surface, as they can dry into permanent features. The surface of tumbled and honed marble will be more forgiving, but the same rules apply there, as well.
It's generally a good idea to seal a marble tile at least twice—and perhaps several times—waiting for each coat to dry before applying a new one. This creates a strong protective layer on the surface of the material. You may need to reseal the tile every 6 to 12 months, depending on how much traffic the room gets.
Grout the Tile
Mix the grout as directed by the manufacturer. As with ceramic tile, use unsanded grout if the joints are 1/8-inch wide or less; used sanded grout for wider joints. As with the mortar, mix only as much as you can apply in about 15 or 20 minutes—the point where the grout starts to set up.
Use a grout float to apply the grout to the joints, using a sweeping motion to force it down into the joints. Running the grout float at a 45 degree angle to the joints will reduce catching edges and result in a full filled joint. Holding the tool slightly on edge can help push the grout downward. Try to direct as much of the mix into the grooves as possible, and wipe up any excess that gets on the tiles. Ideally, the seams between tiles must be fully packed with grout, without void areas.
Wipe the Tiles Clean
Use a large grout sponge that is slightly damp to gently wipe the surface of the marble tiles clean and remove excess grout. Be careful not to allow any moisture to seep down into the grout lines, as this can cause the mix to become muddy and wash out. Also, try to avoid inadvertently pulling the grout out of the joints as you work with the sponge—focus your efforts on the surface of the tiles only.
Allow the grout to cure as directed.
Seal the Grout
Check the grout manufacturer's recommended waiting time before sealing the grout. Waiting for seven days is not uncommon. Seal the grout with a foam brush, following the manufacturer's directions for application.