Asbestos shingles are applied in practically the same way as slate. Over the roofing-boards should be laid slater's felt as for a slate roof, and a cant strip 1/4 by 1 1/2 inches should be nailed along the eaves line to start the first course of asbestos shingles, which should be a double course and overhang the eaves 1 1/2 inches. The average size of asbestos shingles is 9 by 18 inches by 1/4 inch for the lower layer of the first course, and 8 by 16 inches by 1/8 inch for the upper layer of the first course and the other courses. They are laid about 7 inches to the weather, and the ridges and hips may be finished with the Boston hip, or by a specially designed ridge and hip roll. Where the hip roll is used the ridge-pole should project above the roof, or a false one be added so that a substantial nailing can be had for this tile.
The most widely advertised asbestos shingle roofs employ shingles which have rough edges, and which have various shades of coloring, some gray, some red, others reddish brown, and others grayish brown. The causes which led to the development of this type of roof were the artistic failures of the first asbestos shingle roofs. These early roofs were made with shingles which had edges as smooth and sharp as steel plates, surface texture as slick as a trowelled cement floor, and colors of either gray or pale red that were so perfectly matched that at a distance the individual shingles blended into one dead-level plane, so that the roof of the house looked more like the armored plate of a battleship than anything else - it was so perfectly made.