How to Lay Marble Tiles Diagonally
Laying marble tiles on the diagonal changes their appearance from simple squares to dramatic diamonds and is no more difficult than tiling in a standard configuration.
With the tile backer board in place, begin by measuring the areas to be tiled (Image 1).
The tiles used here are pre-attached to mesh-backed mats. Each mat is a section of the overall pattern, and although the tiles in the pattern are different sizes, the mats are easy to install, which saves time.
On a flat surface, place the tiles as they would look installed and check their measurement against the layout (Image 2).
Cut the mats to fit the areas measured. In this project, the ceiling and floor are covered with square 2x2" tiles. On the shower walls, rectangular 2x4” tiles are used. The design also calls for a decorative 3” mosaic border on the walls between the second and third panel from the top.
If the mats can’t be trimmed to fit the space, tiles may have to be cut at one end or another – or at both ends, if you want the end rows to be symmetrical. Here, cuts will be less noticeable if they are made in the bottom row of tiles. Because vertical tile setting starts at the bottom up and works upward, this installation will begin at 72.5 inches down from the top of the shower (based on the mat width measured from the top). The bottom panel will be installed last.
For vertical installations, use a temporary starter board to ensure that the tiles go up straight and the rows stay even. Use a level to position the board and attach it with drywall screws directly onto the cement backing. The board and screws are removed after the tiles have set (Image 3).
Use non-sagging thinset mortar to set tile mats on vertical surfaces. This prevents the tiles from sliding down after they're placed.
Spread the thinset onto the wall with a notched trowel. The size of notches ensure that the right amount of mortar is spread onto the surface—not too thick and not too thin.
Using the starter board as a guide, embed the tiles into the mortar (Image 1).
Once the mat is in place, push the tiles evenly into the thinset. Use your hands, a rubber mallet or a grout float to apply even pressure across he tiles. Wipe the tiles with water and a clean sponge as you set them. Check the level of each row before you set the next one, and use spacers to position and hold the tiles in place while they dry (Images 2 and 3).
If a tile is broken, pull it off the mesh and replace it with one that is intact. Work in a small area and put up a section at a time so the thinset doesn't dry out.
Set the tile panels on the side walls in the same way. If there are gaps at the corners, fill in the spaces with individually cut tiles.
Use a wet saw to make precision cuts and to prevent the tiles from breaking or splitting when cut.
The cut pieces will have a sharp, straight edge that will be obvious against the tumbled marble edges of the uncut tiles. Before you set the pieces along an exposed edge, use a sanding stone to soften their edges
The 3” mosaic border is placed between the second and third panel from the top. The border tile is thicker than the other tile, so apply less thinset when you set it (Images 1, 2 and 3).
Finish setting the tiles on all sides of the shower. If you apply too much thinset and it squeezes out through the joints, take a narrow tool like a screwdriver and rake out the excess (Image 4). If you don't do this before the thinset dries, it will be difficult to remove later and will not match the color of the grout.
The 2x2” floor tiles are installed last. Apply thinset, lay the mats in place and press them down with the rubber float. If the floor has been poured correctly, you don't have to worry about sloping them toward the drain.
Use a tile nipper to cut the angled tiles around the drain into the right shape. Mark each tile and use the nipper to chip away to the mark.
Install small pieces by buttering the back of the tiles with mortar, then set them in place.
The floor tiles are arranged in what is called a pinwheel design. Large 12x12” marble squares are set around a small 1x1” tile offset at the corner.
Apply a layer of thinset to the floor with a notched trowel. As you work, run your hand along the grout spaces to feel where tiles need to be pushed down or elevated. Add thinset to the back of any tiles that need to be raised slightly.
After the floor mortar has dried, use an unsanded grout to fill the gaps between the tiles. Because the tiles are tightly spaced, a smooth mix without aggregates is recommended. Follow the manufacturer's instructions on the bag for mixing the grout that you select.
Apply the grout with a rubber float. Hold the float at a 45-degree angle to prevent pulling the grout out of the joint as you drag the float across the faces of the tiles. Wipe the adjacent surfaces with a sponge or cloth as you work, especially around the baseboard, so the grout doesn't stain them.
In this project, three pieces of polished marble are used for the half wall in the shower. One piece is set on the threshold, another on the vertical part of the half wall, and the third on the horizontal part of the half wall.
Sponge the back of the marble before you set it. Marble is a porous stone, and wetting the bottom before setting prevents pigments in the thinset from migrating through the stone. It also prevents the thinset liquid from being absorbed into the stone, which will make the mortar dry too quickly.
After the floor tile and grout has set, prepare the grout for the shower walls. Use a mix of 75 percent sanded grout and 25 percent unsanded grout. Sanded grout is stronger when it dries, which helps to reinforce vertical tile applications, but sanded grout is difficult to work into tight joints on a vertical surface. Adding unsanded grout thins the mixture so it can be applied more easily.
Mix the grout to a thick, oatmeal-like consistency, and use a rubber float to work the material into the joints. Start at the bottom and work your way up holding the float at a 45-degree angle to the joints (Image 1).
Once all the joints in a section are filled, let it dry a little bit, then wipe the grout off the surface with a sponge and clean water (Image 2).
When all the tiles have been placed and the mortar has set and dried, fixtures can be installed and the finishing touches added. This bath includes a freestanding sink vanity (Image 1).
The newly renovated shower includes a rainfall showerhead (Image 2).