How to Build Ceramic Tile Hearth Pads

Cut the plywood into the desired shape of the hearth pad. Ensure that the size meets or exceeds the minimum size for your stove model. Trace the plywood outline onto the backer board and score along the lines with the utility knife, then snap the backer board upward to cut. If multiple sheets of backer board are required to make the size of the hearth pad, stagger the joints to increase the weight bearing strength of the hearth pad.

Position the plywood in place on the floor and drive a galvanized screw through the top into the floor every 10 inches around the perimeter. Place the backer board on top and screw down into the plywood. If multiple sheets of backer board are needed, use fewer screws in the area where the stove will sit to minimize the risk of a screw conducting heat downward. Add another layer of backer board if you want to increase the insulation value of the hearth pad.

Measure the dimensions of four tiles spaced with tile spacers. Use these measurements to snap a chalk line grid over the face of the hearth pad in the desired tile pattern, each square of the grid representing four spaced tiles.

Spread a quarter-inch layer of thin set onto one grid square with the trowel. Use the notched side of the trowel to furrow the thin set, then set four tiles, spaced with tile spacers, into the thin set. Tap the tiles gently into the thin set, then continue to the next grid square and apply thin set mortar and tiles. Continue until the whole hearth pad is tiled, except for those tiles needing cutting and the edging tile.

Measure the space for each cut tile, then put on eye protection and cut the tiles to size with the tile cutters. Butter the backs of the cut tiles with thin set and put them in place individually. Set the edging tile on the exposed edges of the hearth pad last. Leave the hearth pad overnight to let the mortar cure.

Sweep grout into the joints of the hearth pad tiles with the grout float. Hold the float at an angle to the tile joints and wipe off the excess grout from the tile face with the sponge as you go. Leave the joint between the last row of edging tile and the floor without grout. Apply a line of caulk to this joint and smooth it over with a damp sponge or wet finger. Leave the hearth pad to cure for three days before placing the stove on top.