Installing ceramic tile

Pour the water into a bucket, then add about half the dry thinset. Mix the thinset with a 1/2-inch drill and a mortar paddle. Keep the speed below 300 rpm to avoid introducing air. Add thinset a little at a time. When the thinset is evenly mixed, let it set for 10 minutes before applying.

Whether you have chosen thinset or organic mastic to set your tiles, bring it into the room to acclimate it to normal room temperatures -- ideally between 65 degrees and 75 degrees F. Mix thinset with water that is clean enough to drink and clean out the bucket after each mix; mortar and adhesive residue can cause a new batch to cure prematurely.

Adding the powder to the water a little at a time reduces airborne mortar dust and makes mixing easier. Let the mixture set for 10 minutes so the water will penetrate any remaining lumps. Then mix again to remove lumps. To test the consistency load a trowel with mortar and hold it upside down. If the mortar falls off the trowel easily, add more dry powder and remix. The ideal consistency is as thick as peanut butter. Clean the subfloor before applying thinset adhesive.

Dump mortar at the edge of a section of the room. Holding the straight edge of a trowel at about a 30-degree angle, spread the mortar evenly as thick as the depth of a trowel notch. Spread the mortar to the layout line; comb it with the notched edge at about a 45- to 75-degree angle.

Properly applied thinset forms ridges that compress to cover the entire back of the tile when it is embedded. If thinset is applied too wet, it will not hold these ridges. A dry thinset application will not compress and will result in the tile adhering only to the top of the ridges. Test a thinset mixture occasionally by pulling up a tile and examining the back. If the thinset completely covers the surface, the mixture is correct.

Starting in the center of the room, set the first full tile at the intersection of your layout lines, positioning it with a slight twist as you embed it in the mortar. Do not slide the tile -- sliding can thin out the thinset and push mortar into the joints. Keep the edges of the tile on the layout lines.

Using the layout pattern you have chosen, lay the next tile in place with the same twisting motion, keeping the tile aligned on your layout line. Insert spacers between the tiles and adjust the tiles to fit.

Following the method outlined in step 4, continue setting tiles in a straight line. Trowel on only as much thinset as you'll cover with each row of tile.

Periodically check to make sure the tile conforms to the layout lines in both directions. Lay a long metal straightedge or 4-foot level on the edge of the tile. This edge should align itself with the layout lines. Each joint within the pattern should also be straight. Scrape off any excess thinset that may have spread over a layout line. Adjust the tiles to straighten the joints if necessary.

Continue laying the tiles according to your chosen pattern, spacing and checking them as you go. Don't kneel or walk on set tiles. If you need to straighten a tile that is out of reach, lay down a 2-foot square of 3/4-inch plywood to distribute your weight evenly and avoid disturbing the tile. Cut at least two pieces of plywood to use, so you can position one while kneeling on the other.

The size of the notches in the trowel you use will depend on the thickness of the tile. The depth of the notch, and therefore the ridge it forms in the adhesive, should be about two-thirds the tile thickness. For 6- to 8-inch floor tiles, use a 1/4- to 3/8-inch square-notched trowel; for large tiles (more than 12 inches), use a deep (1/2-inch) square-notched trowel. Combing adhesive so it forms the right-size ridges requires that you hold the trowel at about a 30-degree angle and keep the edges in constant contact with the substrate. If you have trouble making 1/4-inch ridges with a 1/4-inch trowel, switch to a 3/8-inch notch and hold the trowel at a slightly lower angle.

When laying loose tiles (not sheet-mounted), use plastic spacers to keep the tiles the proper width apart.

Insert spacers vertically in the joint after you set each successive tile. That way the tile will move into the correct placement after it is embedded in the mortar. Once you reach a point where tiles form corners, flip the spacer down into the corner. Pull the spacers before grouting, even if the manufacturer's instructions indicate that you can leave them in place. Spacers may show through the grout.