How to Tile a Floor

The quality of your finished ceramic tile project depends on the quality of the surface beneath it. Before starting, remove any existing ceramic tiles and ensure your floor is flat and strong enough to meet industry standards (two layers of plywood totalling 1 1/4-inch thickness).

Smooth out hollows and valleys with self-leveling underlayment and/or reduce the height your installation by using plywood alternatives (Ex. 1/4-inch WonderBoard or 5mm EasyMat). Consider applying a waterproofing and anti-fracture membrane where needed for moisture protection or to prevent tile or stone from cracking.

Use the latex-modified thinset mortar specified for your tile. If you're installing porcelain tile, buy mortar made specifically for porcelain since it is designed to stick to porcelain's nonporous surface.

Mix the mortar according to the directions on the bag. Wear safety glasses, a dust mask, and rubber gloves to protect your skin from the mortar, which is caustic. Don't mix too big a batch since the adhesive has a limited working life. If it starts to harden, you have to discard it. A second batch will be created in Step 7.

Using a chalk line, snap grid lines on the floor to mark the dimensions of the sheets. Plan so that joints in the backerboard – a thin layer of concrete with fibreglass mesh on both sides – won't line up with seams in the subfloor so that your four corners will never meet.

With the smooth side of a 1/4-inch notched trowel, spread enough adhesive for one sheet. Ridge the adhesive with the notched side of the trowel.

Score the backerboard on both sides and place a sheet on the wet adhesive. Leave a ¼-inch gap between the backerboard and the wall and a 1/8-inch gap between the backerboard sheets. Drive backerboard screws into the sheet every 8 inches. Position the screws at least 1/2 inch around the perimeter but no more than 2 inches from the edge.

Once all sheets are in place, fill the spaces between the boards using adhesive with a margin trowel or the flat side of a notched trowel.

Smooth the adhesive so it extends about 1 1/2 inches on each side of the joint then cover the joints with 2-inch vinyl-coated fibreglass tape, pushing firmly into the adhesive. Once embedded, scrape off any excess adhesive from both sides of the tape. Cover the tape with a second layer of adhesive then feather the edges with the smooth edge of the trowel.

Along the perimeter of the room, mark the centre on opposite sides. Snap a chalk line linking one mark to the other. Measure and mark the centre of the line. Use a framing square to establish a second line perpendicular to the first and snap a second line across the room.

Check for squareness by marking 3 feet vertical and 4 feet horizontal from the intersecting point. Measure the diagonal between the two points. A 5 foot measurement ensures the lines are square.

Lay tiles and spacers along one line from the centre to the wall. If the space between the last full tile and the wall is narrower than half a tile, move the line parallel to that wall back by half a tile. You'll end up with wider cuts at both walls.

In order to divide the floor into manageable boxes – roughly 2x3 feet square – layout your tiles in a box formation at the gridline intersection and measure the length. Add the width of one spacer to each measurement. Remove the tiles and lay out a chalk-line grid, using your sample box measurements for each square on the grid. Mix another batch of thinset mortar adhesive.

Starting at the intersection box on the grid, put a little adhesive on the flat side of a square-notched trowel. Apply the adhesive by pressing it into the face of the backerboard drag it across with the trowel. Apply more to make a layer of adhesive roughly 1/2-inch thick.

Then, hold the trowel at a 45-degree angle to the floor pushing the teeth of the tool to the floor while dragging the trowel and making ridges of uniform height in one direction in the adhesive. Trowel notches should be the same size as the thickness of the tiles being set.

Double-check the consistency of the adhesive by placing two tiles next to each other in the adhesive with a spacer in between. Press both firmly into the adhesive. Pull a tile up and look at its bottom. The back of the tile should be covered with adhesive. If you see only parallel mortar lines, the adhesive is too dry. If the mortar squeezes up between the tiles, the bed is too thin and you need to drop the angle of the trowel as you comb. If the ridges in the adhesive have left more or less solid lines on the tile, the bed is too thin and you need to raise the angle of your trowel. If the mortar on the floor fails to stay in ridges, it is too wet.

Lay the first tile into the adhesive and firmly press. Remove excess adhesive from the tile with a damp sponge or cloth. Place the second tile alongside the first, spacing it with spacers. Continue laying tiles until the gridline box is filled.

Lay spacers flat in the corners where tiles meet. Lay a short length 2x4 or beater block on top of the tiles and tap lightly with a rubber mallet to level the tiles. Repeat with every gridline box until the floor is covered. If a full tile cannot be set, follow Step 11.

Perform this step after all full tiles have been set. Place the tile to be cut directly over the last set tile. Set another tile, the "marker tile," on top of it, butting it against a tile set on the edge at the wall. Trace along the marker tile to mark the cutting line on the tile below.

Place the marked tile on the cutter and align the cutting line with a scoring tool. Pull or push the cutter along the top of the tile with a single, firm stroke. Wearing safety goggles, press down on the handle of the cutter to snap the tile. Prepare to set, lay and level the cut tile(s).

Apply one to three and a half litres of grout on the tiles. Holding a hard-edged rubber grout float at a 30-degree angle, spread the material in sweeping arcs, pressing it into the joints to fill them completely.

Remove excess grout by holding the grout float at a 90-degree angle and sweeping it diagonally across the tiles. Work diagonally across the joints to avoid dipping into the joints.

Wait a few minutes for the grout to start hardening. Wipe the tiles in a circular motion with a barely damp sponge to remove grout residue. Once the grout has hardened, the tiles will be left with a slight haze on them.

Clean it up by going over the area lightly with a damp cloth, then buff immediately with a dry cloth. Let the grout dry for the length of time recommended by the manufacturer before applying the sealer.

Damp cure the grout by misting it twice a day for three days. After letting the grout cure for 48–72 hours, spread the sealer along the grout lines with a small paintbrush or a sealer applicator. Clean off any smears within the first five minutes or so. Then let the grout dry for at least 24 hours.

Fill expansion gaps with caulk. Caulk will flex if the floor expands or contracts as the weather changes. In wet areas, in front of a bathtub or shower, or wherever the expansion gap will not be covered with shoe moulding, fill the gap with caulk and smooth it with a wet finger.