Wood in any form serves as a poor subfloor for stone tile. Wood naturally warps, twists, swells and shrinks due to change in temperature or humidity. This movement can cause any tiles installed on the surface of the wood to crack or break. Rather than installing tile directly to the wood, take the time to properly prepare the wood for tile. The first step in preparing wood floors to receive new tile involves securing plywood subfloors. Cover the entire surface with 1/2-inch thick sheets of plywood. Secure the plywood to the wood floor below using 1-1/4 inch screws every 6 inches along the edges of the boards. This creates a stable support base for the tile. Next, cover the plywood with a 1/2-inch layer of cement board. Secure the cement board with a thin layer of thinset mortar. Cover the seams between each board with cement board seam tape, then screw the cement board to the floor using cement board screws every 6 inches along the edges. Before you install tile, measure along each wall to find the center point. Snap a chalk line from each of these center points to the one opposite. The point where these lines meet represents the center of the coverage area. By starting your tile installation at this point, you can mask any walls that are uneven or out-of-plumb. Start laying out your tiles at the center point without using mortar. Keep laying out the tiles until you've found your desired layout or pattern. You may wish to number the tiles or make a quick sketch to keep tricky patterns organized. Before applying mortar, cut tiles as needed to fit your pattern. Wear safety glasses and use a wet saw with a diamond blade for smooth, even cuts. Spread thinset over a small section of the floor using a 1/4" notched trowel. Lay your tiles into the thinset, using spacers to maintain even grout lines between each tile. Continue applying a small amount of thinset and laying tiles until you've covered the entire floor. Seal the faces of the stones with a natural stone sealant to protect from grout dyes bleeding onto the stones. Try to avoid sealant from dripping into the grout joints, as this will not allow the grout to bond to the stone and allow water and moisture to seep through. We recommend allowing new tile to dry for 24 hours prior to grouting. After this waiting period has passed, mix your grout according to the instructions on the package. Properly mixed grout has a consistency similar to peanut butter, so it's important not to use too much water. Once the grout is mixed, pour a small amount over a section of the floor. Use a grout float to push the grout into the joints between your stones. Repeat this process until you've filled all the joints with grout, then immediately begin wiping excess grout off the face of the tiles using a wet sponge. You may need to wipe the tiles several times to remove all grout from the surface. Allow the grout to dry for 24 hours before sealing the whole floor a second time. Allow additional 24 hours before walking on the tiles.

Hope this helps.

Joanna