Tile requires a firm, flat base under it to prevent any movement that could crack the tiles or the grout between the tiles. Wood isn’t the best choice (cement or cement board is better), but in some circumstances you can tile right over a wooden floor. The wood must be solid and unbroken, with no loose areas. Don’t tile over wood in a bathroom or other wet area, as the moisture can soften the wood over time and cause the tiles to fail.
Pour liquid floor leveller over the wood floor to fill in any cracks, gaps or low spots and let it level itself out. Allow it to set for 24 hours.
Divide the floor into four square sections, using your chalk snap line to lay two intersecting lines across the floor. Put a carpenter’s square at the intersection to make sure it’s exactly perpendicular before you snap the second line.
Apply thinset mortar over the intersection of the lines using a notched tiling trowel. Press four tiles in place at the intersection, putting tile spacers between them.
Spread more mortar and lay more tiles, working out from the middle of the floor toward the edges. Put tile spacers between all of them. Cut the tiles at the edges by the walls, using a tile cutter. Let the tiles set overnight.
Pull out the spacers. Use a grout float to grout the floor, spreading the grout over the tile surface and pressing it into the lines between the tiles. Use a damp sponge to wipe up the excess grout. Let it set for two days or more before walking on it.
Wear eye protection when you cut the tiles.