For our tub surround, we chose polished 12-in. square marble tile and unpolished 1-in. square limestone accent tiles. We cut the 4-in. square accent tiles and 3 x 12-in. border tiles from the 12-in.marble. You can mix and match stone or buy ready-made patterns at tile stores. Tile dealers usually have sample displays where you can find ideas, or they'll steer you to designers who can guide you through the vast maze of materials. Just keep a few basics in mind: Lay out each wall on graph paper, tile for tile; start the pattern from a center line (Photo 5); and use tiles that are all the same thickness and that use the same grout. Plan to use unsanded grout for grout lines up to 1/8 in. wide and sanded grout for wider lines. The grout lines in our pattern ranged from 1/16 in. to 1/8 in.
Prices for natural stone range from inexpensive to exorbitant, but keep in mind that expensive stone isn't necessarily better – it's just less common. Granite is much harder and more durable than marble and limestone, but curves and holes are tougher to cut and require somewhat different techniques. You have to use diamond-blade tools only, not the carbide-grit hole saws and jigsaw blades we show here for marble.
Before beginning any work on the walls, protect the tub. Tubs are easily chipped and scratched and expensive to repair. Cover the tub with tape around the edges, and lay a 58-in. long piece of 1/2-in. plywood over rigid insulation or heavy cardboard on the tub rim. Replace it with a dropcloth during tiling, and check frequently in the bottom of the tub for debris that might scratch the finish.
The first step is installing tile backer on the wall. We like to use cement board for areas that have to withstand frequent wetting such as a shower, but other types of tile backers will work as well. Check with your local building inspector for the approved types in your region. Add blocking if necessary to make sure your cement board ends catch at least 1/2 in. of framing. And add extra blocking to catch screws from grab bars if you intend to put some up. Small quantities of moisture can wick through tiled walls, and grout and caulk may develop cracks over time from building movement, so staple either a No. 15 felt or 4-mil polyethylene vapor barrier behind the cement board.
Measure each section of wall, subtract 1/4 in. to compensate for rough edges, and cut the cement board (Photo 1). Cement board consists of two layers of fiberglass mesh sandwiched around a cement and sand core. Score one side to cut the fiberglass mesh, then snap it like drywall. You'll dull your knife blades, so have a few extra handy or buy a special carbide scoring tool that'll last a lot longer. Set the cement board on the tub flange, then screw it to the studs about every 8 in. with special cement board screws (available at tile stores and home centers).
It's easiest to make clean hole cutouts or curves with a carbide-grit jigsaw blade and a 1-1/4 in. carbide-grit hole saw. But in a pinch, you can use the crude, messy method of scoring the front and back of the hole and breaking it out with a hammer.
Use a special alkali-resistant mesh tape and thin-set mortar to cover the joints (Photo 4), including the joint at the drywall. Use regular joint compound in areas that won't be fully covered by tile. Prime regular joint compound before tiling.
Draw a plumb line at the center of the back wall, then measure over to the side to see how many tiles will fit. You want to end up with at least half a tile at each corner, so depending on the size of your tile, either place the edge of your first tile at the center line, or center a tile over it as we did (Photo 5).
If your tub is perfectly level, draw a level horizontal line at the height of one tile plus 1/8 in. (for caulk) above the rim. If the tub isn't level, find the low point, and start your horizontal guideline from that point. You'll then have to shave most tiles in the bottom row as you go to maintain the 1/8-in. gap. This is where the diamond saw comes in handy!
Draw additional lines for feature tiles or pattern changes. Remember to double-check horizontal and vertical lines to make sure they form true squares. Any sloppiness with the level at this point will cause headaches later during tiling.
Lay out the end walls so that cut tiles fall in the corner, where they're less obvious. Our installation called for a 3-in. border tile, which we ran down the side of the tub, so we drew a plumb line 3-1/8 in. from the tub (remember to leave a caulk gap next to the tub), then worked back to the corner with full tiles, ending up with a 7-in. cut tile. The two basic rules for layouts are to hide cut edges whenever possible, and to make a layout that looks symmetrical and pleasing to the eye.
Hold to these lines as you work up the walls, and make slight adjustments in the corner tile cuts and grout lines as you go. Stand back every once in a while to look over the wall, and straighten any tiles that seem off.
Mix the mortar according to instructions on the bag. Marble and natural stone are installed with thin-set mortar mixed with latex additives for better bonding. Use white mortar for light-colored stone; darker mortars can darken the stone.
Use a 1/4 x 3/8-in. square notch trowel for 12-in. square marble tile. Hold the trowel at a 45-degree angle to create deep ridges (Photo 5). Spread no more than you can tile in 15 minutes or so. If the mud skins over and doesn't adhere, scrape it off and put a fresh batch on.
Use 1/8-in. spacers to hold the first row of tiles up off the tub (we used nails), then place tile spacers between the tiles to create even grout lines. Thin-set mortar doesn't grab right away; the tiles will slip down if unsupported. We used 1/16-in. spacers for tight grout lines between the 12-in. squares and 1/8-in. spacers in the decorative band (Photo 12). The 1-in. tiles were mounted on mesh. We used 4d finish nails to anchor them until the mortar set (Photo 12).
Cuts are simple and straightforward with a diamond blade wet saw (Photo 8). But push the tile through slowly. Part of the visual charm of marble is its flaws and fracture lines, but these are also weak points where the stone can easily break, especially at the end of a cut. You may have to cut in from each end about an inch before completing cuts (Photo 10).
Saw cuts leave slightly rough edges. Smooth these with 200-grit wet/dry sandpaper. (For granite, use a special rub stone.)
Cutting the holes for the tub spout, faucet and shower head can be tricky (Photos 9 – 11). Some marble tiles are fragile, so fully support the tile with plywood when cutting or drilling it. And work carefully near brittle edges and corners. Keep in mind that you can have a tile store do these cuts for you if you don't want to attempt them.
After the tiles have set for at least a day, the wall is ready to grout. Pull out all the spacers and clean off any mortar on the tile faces or projecting from the grout lines. Then coat the marble with a grout remover or tile sealer to prevent staining and to make grout removal easier.
Mix the grout (with water only for marble) to a smooth peanut butter consistency, and let it sit for the time listed in the directions. Don't mix the whole container of grout at once. Start with a quarter or third of a container, and mix more as you need it. Remix, then work it into the grout joints with a special grout float (Photo 13). This is fairly hard work—use two hands and pack the joints full. Then scrape the edge of the float diagonally across the tile to remove excess.
Stop after about 15 minutes and clean the grout off the surface with a damp (not wet) tiling sponge, rubbing it in a circular motion. Be careful not to wipe out the grout from the joints. Keep a little grout on hand to fill in air bubbles and voids. Rinse the sponge often, but don't worry about getting the tile perfectly clean yet.
Wipe grout into the joint between the trim and drywall to create a finished-looking edge. Then clean all grout from the corners and the joint along the tub. You'll caulk these joints later (Photo 14).
After an hour, polish the haze off the tile with a dry towel. Some of the grout lines may look a little sloppy—rub the edges with the towel to sharpen the lines. Then wet down the tile and grout lines once a day for the next few days to help the grout cure. Finally, apply a tile sealer according to manufacturer's directions.
After the grout has dried for at least a day, fill all corners with a caulk designed for tubs and tile. (Check tile stores for a color that matches your grout.) Taping the edges of the caulk lines gives you cleaner, more precise caulk lines (Photo 14). Just remember to remove the tape as soon as you finish smoothing. Caulk starts skinning over within a few minutes, and if you wait too long, the tape will smear caulk on the wall.
Caulk the joint between the tub base and floor as well. The floor under our tub had a 1/4-in. sag in the center that was too large for a good-looking caulk joint. So we covered the edge with a limestone trim piece—a standard floor threshold with one edge cut square (Photo 15).
If you wish, buy soap dishes or towel bars and mount them with silicone at comfortable heights. Tape them in place overnight until the silicone sets, then caulk around the edges.
Finally, install the faucet trim and tub and shower spouts, plug in the tub, and enjoy the fruits of your labor—if you can get in before someone else does!