Lay a Ceramic Tile Floor

When it comes to flooring, tile is about as ancient—and attractive—as it gets. Nothing beats tile for a smooth, tough, carefree floor in a kitchen or bathroom, especially with such a wide array of ceramic and stone tiles on the market.

Ceramic, marble, and granite all make great floors. Although they are similar to work with, ultra-hard granite is the toughest to shape, and soft ceramic is the easiest. However, a rented tile saw, or wet saw, will cut any of these materials, so difficulty in cutting should not be a deciding factor in material selection. Price, however, may be; ceramic is at the bottom of the price heap, granite is at the top, and marble is midway in between.

Step 1: Preparing to Tile

Tiling, like its big brother, masonry, requires a unique frame of mind. It's a permanent material, and that means you must be wise in your choice of color, material, surface, and design. You have to work carefully and get it right the first time, because repairs are difficult if not impossible. Most importantly, you must let the mortar and grout set the pace. When they are hurrying to set, you have to hurry as well. When they are sluggish, you've gotta hit the brakes.

The choice of tile and grout is largely a matter of taste. Larger tiles are faster to lay and grout, but they may make a small room feel cramped. Tile size also affects joint width. Wide joints (say ¹⁄₄") make sense with big tiles. Narrow joints can magnify tiny discrepancies in tile size or placement.

Tile needs a firm base, the stronger the better. Ideally, your existing floor is 1 ¹⁄₄"-thick plywood or oriented strand board, supported by joists placed on 16" centers—16" from center to center. To be on the safe side, I start by rescrewing the plywood to the joists with 2" construction screws, placed every 12" or so.

Cleaning Out the Old

Preparation starts by removing appliances, furniture, and molding. Strip up any previous flooring that comes up relatively easily. If you can't strip securely glued flooring, lay the cement board onto lines of construction glue. The lines should be 8" apart, on top of each joist, and centered between the joists.

Cutting the Underlayment

Cement board, sold as WonderBoard and Ducock, is an excellent base for tile: rigid, waterproof, cheap, and flat. The only disadvantage: It instantly dulls knife blades. We use a jumbo drywall square, a utility knife, and plenty of blades to cut cement board. Cut one side (the label tells which), fold and break the board, and cut the other side. Stagger the joints so four corners don't meet, and place joints on top of the joists where possible.

Mortaring the Underlayment

The whole point of underlayment is to make a flat, stable base for the tiles. Underlayment gets laid in the same mortar bed you'll use for the tiles.

Once the boards are cut, mix thinset tile mortar and start laying underlayment:

1. Trowel mortar onto the plywood, following the same procedure used to mortar tiles.

2. Working quickly, lay the boards down, taking care to press the edges down. Don't wait too long, or the boards might rest not depress the mortar uniformly.

3. Screw the boards with 1¹⁄₄" cement-board screws, placed about 8" apart. If the screws are hard to drive, drill quick pilot holes for them. We screw underlayment with a screw gun, which shuts off when the screw reaches the right depth, but an electric drill would also work. Don't drive the screws too deep; that damages the cement board.

4. Use a straightedge to check flatness as you work.

5. Fill joints between boards with mortar.

Step 2: Where to Start Tiling?

Finding the starting line can be the toughest part of tiling. It's helpful to start tiling in a corner. A triangle 3' × 4' × 5' is a right triangle. Measure a “3-4-5” triangle in your starting corner to check if it's square. You can get into big trouble by assuming your starting corner is square.

There are two methods for finding a starting line, depending on how the tile fits the room. In the next section we'll take a look at both.

Choose Your Method

In Method A, you start on a center line. Place a joint along the center of the longer dimension of the room. Measure outward and calculate the width of the last row of tiles at the walls. If you will have pieces narrower than 2" or 3" (which are hard to lay but easy to damage), try Method B.

In Method B, you start parallel to a straight wall. Lay the first row along the longest straight wall, and let the chips (in this case, the smaller tiles) fall where they may.

Plastic spacers are a good way to keep the layout honest, both while testing fit and while laying. You're supposed to place the spacers flat on the floor, at the corners, but they're easier to place and remove in the standing position.

Here's a related cheat: Screw straight scraps of wood where tile meets carpet. Snug the tile against the wood to make a straight outside edge.

These methods for choosing where to begin laying out your tile will also be helpful should you decide to install wood strip or laminate flooring.

Cutting the Tile

I've already described how to choose a cutting technique. You can break most ceramic tiles with a tile breaker, which scores the tile and then presses it down across the score line. We rented a wet saw—which uses water to cool a diamond blade, because it's easier to use and can trim hairline amounts from the edge of tiles. Try to place cut edges toward the walls, because they will be either sharp (from a saw) or rough (from a tile breaker).

Step 3: Laying Tile

With a good bed of mortar and accurate cuts, it's tough to lay a bad tile. Tiling has these basic steps:

1. Lay down mortar.

2. Place each tile position in the mud and rotate into position.

3. Beat (tap firmly on) the tile with a 12" block of 2 × 4.

Shimmying and rotation both push the tile into the mortar.

Use the beating block to check that each tile is level with its neighbors. Work fast to make adjustments before the mortar sets, and don't kill yourself aiming for thousandth-of-an-inch accuracy; ¹⁄₁₆" accuracy is just fine.

After you level the tiles, place the spacers to set the joint width. After you lay a few tiles, check the level with a straight 1 × 4. If you work quickly, the mortar will be soft enough to adjust the tile level. Continue checking the level as you work: The straightedge never lies!

As you set tiles, don't let mortar build up in the joints. Use a screwdriver and a wet rag to clear out mortar so none remains above the surface after you grout.

I beat the last tile into place with a 2 × 4. Then I use the beater to check that the tile is level with its neighbors.

Step 4: Great Grout

Once the tiles are laid, give the mortar 24 hours to set. Assemble your grouting tools. It pays to have a range of trowels on hand to fill the joints. Some people prefer using the straight edge of a toothed tiling trowel. I prefer a drywall knife, sometimes assisted by a second trowel. The goal is to find a fast system that completely fills the joints.

Mix the grout, allow it to rest 10 minutes, and mix again.

If the grout starts getting too stiff, it won't go into the joints. Throw it out and mix more.

Keep an eye on how the grout is setting. After five minutes, test the consistency to see if your finger can shape it.

You may be tempted to buy a jointing tool to form the grout lines, but fingers often work better. Jointing tools tend to dig too deep in a wide joint, and ride up in a narrow one. A gloved finger, on the other hand, adapts nicely to varying widths. You may need to run your finger back and forth to smooth the joint. In a few minutes, scrape diagonally across the surface with a wide trowel to remove spilled grout.

As the grout sets, you can clean the floor more vigorously without harming the joint. When the grout is sufficiently set, sponge diagonally across the entire floor to remove smeared grout. Clean the sponge in a bucket, but keep it relatively dry. Cleaning goes fast if you catch the grout at the right degree of setting.

When the grout is fairly hard, a damp sponge will do a final smoothing. Run it along the joint, adding a bit of water if necessary to smooth out the joint. Don't overwork the joint—stop when it's smooth enough.

After the grouting is done, leave everything alone for 24 hours so the grout can harden. After a few weeks, a silicon grout treatment can reduce staining, but it's not mandatory.

Excerpted from The Complete Idiot's Guide to Simple Home Improvements © 2004 by David J. Tenenbaum. All rights reserved including the right of reproduction in whole or in part in any form. Used by arrangement with Alpha Books, a member of Penguin Group (USA) Inc.

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