Demolish the existing floor down to the underlayment. If the underlayment is solid, use it as the base for the new tile floor. If the underlayment is in poor condition – marked by crumbling or deteriorating material – you’ll need to pull that up and install a new underlayment. Talk to a tile distributor for what material will be the best for the project.
The material for the field of this slate floor project is a 12x12 inch "Rye with Red" slate – which will be installed on the diagonal. The border measures 8-3/4 inches in width and will consist of two parts – a 4-inch decorative border composed of 1x3 inch slate tiles and a back border made of field tiles cut to fit.
Find the center focal point of the room. Find the center of each wall, and snap a red chalk line to mark each axis. Where the two lines meet is the center or focal point of the room. Mark the border on the floor using a straightedge and pencil or blue chalk line.
Dry set the 12x12 slate tiles on the diagonal along each axis all the way to the border starting at the center of the room. The goal of this step is to space the tile so that it looks like there are equal cuts on either side where the field tile meets the border.
If the cuts are drastically different on either side of an axis where it hits the border, adjust the tile to create the illusion that the tile cuts match. To do this, adjust from the center of the room. Divide the tile that starts at the center into quarters and shift the row over a quarter – this should open up the cuts.
Once you have decided on the starting point for that first tile at the center of the room – mark that location. Create a four-tile template starting at that first tile. Space it out with 1/8 inch spacers. Trace that tile template onto the floor, remove the template and snap a red chalk line on each axis of the traced template. The grid that you’re creating will be the guideline for setting the field tile.