Measure the width and length of the deck with a tape measure to determine how many sheets of plywood backer board will be needed to cover the deck. Sheets of plywood typically measure 4-feet wide by 8-feet long. Divide the width by "4" and the length by "8" to find the number of plywood sheets you will need. Measure and cut the plywood to fit areas where a full sheet will be too big. Transfer the measurements to a sheet of plywood and make a mark with a pencil. Cut the sheet of plywood along the pencil mark with the table saw.
Lay the sheets of plywood on the decking and attach them using screws and a power drill. Place the screws 6 to 8 inches apart when securing them to the decking.
Lay the waterproof membrane over top of the plywood backer board. The waterproof membrane will keep water and moisture from damaging the plywood backer board. Secure the membrane to the plywood backer board using a staple gun. Place staples every 6 inches over the entire area of the deck. Cut the excess membrane around the edges of the deck with a utility knife.
Apply mortar over the waterproof membrane using a trowel. Mix the mortar in a bucket with water by following the instructions on the package of mortar mix. Place a small amount of mortar on the waterproof membrane with a trowel and spread it out.
Drag the edge of the trowel with the grooves at a 45-degree angle to create notches in the mortar.
Place the first piece of tile on the mortar and press down to create a secure bond. Place the second piece of tile next to the first one. Insert a tile spacer between the tiles. Repeat the previous three steps to finish laying the tile over the deck.
Wait for the tile to dry. Apply grout to complete the installation. Place grout on a section of the tile and pull with the grout float to fill in the grout lines.