How to Install Tile at a 45-Degree Angle

Remove the old floor by chipping away at the existing surface with a hammer and chisel until you're down to the subfloor. Vacuum the floor to remove any debris and clean it with a cleanser to remove any impurities which may prevent mortar from adhering properly.

Inspect the subfloor. If it's damaged, tear it up and replace it with WonderBoard. Lay the WonderBoard by staggering the boards so that the corners don't meet up at any adjacent points and drive in a nail every four inches.

Measure the halfway point at each wall and make a small mark at the bottom of the wall. Temporarily drive a nail partway into the floor next to each of the marks. Hook the end of a chalk line to one of the nails. Run the chalk line straight across the room to the next nail, wrap it around, and snap the chalk line. Repeat this with the other walls. This will divide the room into four equal quadrants, with the spot where the lines intersect being the center of the room.

Mix a batch of thinset mortar by following the instructions on the package.

Pick a quadrant to begin in and apply a layer of thinset to cover an area 2 feet by 3 feet in one of the corners by the wall. Use the smooth edge of the trowel to spread the mortar.

Hold the trowel at a 45-degree angle and with a broad, curved wiping motion, create notches in the mortar with the notched edge of the trowel. Finish with a final pass the makes the notches go in a straight line.

Lay the first tile in the corner at an angle so that two corners of the tile are pointing at the wall in front of you and the wall next to you, with tile spacers separating the walls and the corners of the tile.

Put a tile spacer next to the corner of the tile and lay another tile next to it the same way you laid the first. Continue adding thinset to the subfloor and laying the tile in this fashion until you reach the chalk line, then lay the next row the same way until the quadrant is done.

Go to the next quadrant and lay the tile the same way that you did for the first quadrant, except instead of starting at the corner where the walls meet, start along the wall next to the last tile that you laid in the first row. Continue this process until all four quadrants have been completed except for along the walls where you'll need to place cut tiles.

Measure the dimensions of the areas where you'll need to cut tiles and count how many you need at each size.

Cut one tile at each size needed with a wet saw and using them as templates, mark cut lines on other tiles with a pen or pencil and cut as many tiles as you'll need. Cut the tiles by placing the tile against the guide on the wet saw and lining it up so the the blade is aligned with the pencil mark, then make the cut by slowly moving the tile into the blade. Don't force it; let the saw do the work.

Lay the cut tiles in place on the floor and give the mortar about an hour to set.

Scrape away any mortar that might have oozed through the tiles with a straight-edge tool and remove the spacers with needle-nose pliers.

Mix a batch of grout by following the directions on the packaging.

Starting in one of the back corners, lay one or two scoops of grout on the floor and spread it into the tiles with a grout float. Hold the grout float at a 30-degree angle and use a wiping motion at an angle to the tiles so you're sweeping over the corner of the tiles and going diagonally across them. Go over the area several times to make sure the gaps between the tiles are completely filled.

Wipe any excess grout into the next section of tile and repeat these steps until the entire floor has been grouted.

Allow the grout to set for the time specified in the instructions (usually about 20 minutes).

Wipe up any excess grout with a damp sponge. Rinse the sponge frequently and squeeze out as much water as possible.

Wait about 45 minutes, then wipe away the haze that covers the tile with a paper towel.