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How to Install Natural Stone Tile: Installing the Tile Backer
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. Cement board consists of two layers of fiberglass mesh sandwiched around a cement and sand core. You 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 ($8) 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 ($10) and a 1-1/4 in. carbide-grit hole saw (about $10). 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 ($5 at tile dealers) and thin-set mortar to cover the joints, 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.
Figure A: Tile/Tub Details
Click image to enlarge.
Mark the Tile Layout
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.
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.
Install the Tile
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. 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 ($5) 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. The 1-in. tiles were mounted on mesh. We used 4d finish nails to anchor them until the mortar set.
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