How to Lay Tile Flooring Over Plywood

Plywood isn't the best underlayment for floor tiles (cement board is), but plywood is acceptable in certain circumstances. It needs to be solid and immobile, and it's a good idea to coat it with a moisture-blocking primer before laying the tile. The tile itself should be thick (at least 1/2 inch) and not overly large (no more than eight inches across). Don't ever use plywood as tile floor underlayment in a bathroom or other room that's going to see a lot of direct moisture, as the moisture can soften the plywood and crack the tiles.

Things You'll Need

• Flooring nails
• Hammer
• Moisture-blocking primer
• Paint roller with floor handle
• Chalk line
• Square
• Tile mortar
• Mortar trowel (notched)
• 1/2-inch-thick floor tiles
• Tile spacers
• Tile cutter
• Grout
• Rubber grout trowel
• Sponge

Instructions

1. Stand on each part of the plywood underlayment, looking for any sign of movement. Use your hammer to sink several flooring nails at any point where the floor moves at all.

2. Use your paint roller and floor handle to spread a layer of moisture-blocking primer over the plywood, covering it completely. Let it dry for 48 hours.

3. Stretch your chalk line across the middle of the floor in one direction and snap the line. Stretch the chalk line in the perpendicular direction, lay a square between the string and the previously marked line, and adjust the position of the string to make the two lines square. Snap the line.

4. Use your mortar trowel to spread tiling mortar over a few square feet at the center of the floor, where the two lines intersect. Spread enough mortar to lay four tiles.

5. Press the first four tiles into place at the intersection of the two lines, putting tile spacers between them. Spread additional mortar and lay more tiles, working your way toward the walls and using the lines as guides. Put spacers between all of them. Cut the final pieces, by walls, on your tile cutter. Let the mortar dry overnight.

6. Pull out the spacers. Spread grout over the tiles in sections of a few square feet, starting in one corner and working your way across. For each section, scrape the rubber grout trowel across the surface of the floor, pressing the grout into the spaces. Let the grout sit in the spaces for about 10 minutes, then wipe the excess grout off the surface with a damp sponge. Let the grout cure for two days before using the floor.

Tips & Warnings

• Wear eye protection during tile cutting.

References

• Installing Tile Over Subfloor