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 ¼ by 1½ 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 1½ inches. The average size of
asbestos shingles is 9 by 18 inches by ¼ inch for the lower layer of
the first course, and 8 by 16 inches by ⅛ 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.