How to Lay Cement Tiles on a Roof

Measure the length of any valleys in the roof where two sloping sections meet. Transfer these measurements to pieces of V-shaped metal flashing and cut the flashing pieces to size with tin snips. Dot the back of the flashing pieces with silicone adhesive, press them down into the valleys, and drive a galvanized nail into each flashing piece at the four corners and roughly every 6 inches around the edge.

Measure the length of the roof’s eaves. Transfer these measurements to straight metal flashing pieces and cut the flashing with tin snips. Apply silicone adhesive dots to the back, press the flashing down so that it hangs off the eaves by about 2 inches, and nail the flashing into place.

Center a strip of roofing felt, long enough to cover the entire length of the valley, into each valley of the roof. Secure the felt with ¼-inch staples on each side around the outer edges.

Cut a roofing felt strip for the first eave of the roof long enough to hang off each edge by 1 inch. Use ¼-inch nails to attach the strip to the roof deck. Install additional rows of felt, each overlapping the one before by about 6 inches, up the roof to the peak, and then apply felt on the other side of the roof.

Measure up from the eave of the roof, the same distance as the height of the roof tiles minus 1 inch, at each edge of the roof. For 24-inch roof tiles, for instance, measure up 23 inches at each edge and drive a nail into the roof at this height so that the nail sticks out of the roof by 1 inch. Tie a string between the nails.

Apply mortar to the roof from the string line bottom edge of the roof to a depth of 2 inches with a notched trowel. Place the first cement tile at one edge of the roof, so that it hangs off the side by 1 inch and the eave by an inch, and press down lightly to secure the tile in the mortar.

Measure up from the tops of the first row of tiles at each end the same distance as 2/3 of the tile height. For example, for 24-inch tile, measure up 16 inches, and move the nails and string up to this height. Apply a 2-inch bed of mortar below the string, over the surface of the roof and over the top 6 inches of the first row of tiles. Press the cement tiles down into the mortar so that the tops line up with the string.

Continue up the roof like this, layering mortar beds and tiles, until you reach the peak, and then move to the other side of the roof. Use cement roof caps at the top of the roof, installing the caps with a mortar bed.