Coal Tar Pitch Roofing Handbook - 1896 - Pages 9 and 10
THE first Specification presented is for a Standard Slag or Gravel Roof laid over boards. A Roof of this kind is adapted for use on all kinds of buildings (except where the roof is very steep), and is pre-eminently the best for most purposes. Its cost per year of service is much less than any other form of reliable roof covering known. As compared with Tin and Metal Roofing, it is immeasurably superior and more economical, as it requires no painting and no repairs of any kind for years after it has been laid. In fact, any reputable contractor will guarantee such a roof for at least ten years. This may seem a long time, but experience has proven that, with ordinary care, most roofs laid according to this Specification will give good service for nearer twenty years.
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The Barrett Specification
for Standard Slag or Gravel Roofing
(To follow description of Roof Sheathing.)
Over the foregoing shall be laid a (5) ply Coal Tar Pitch, Felt, and Slag or Gravel Roof, to be constructed as follows:
The Rosin Sized Sheathing Paper or Unsaturated Felt to be used shall weigh not less than five (5) pounds per one hundred square feet.
The Tarred Felt shall weigh not less than fourteen (14) pounds per one hundred square feet, single thickness.
The Pitch shall be the best quality of straight run coal tar pitch, distilled direct from American coal tar, and there shall be used not less than one hundred and twenty (120) pounds (gross weight) per one hundred square feet of completed roof.
The nailing shall be done with threepenny barbed wire roofing nails driven through tin discs.
The Slag or Gravel shall be of such a grade that no particles shall exceed five-eighths (5/8) of an inch or be less than one-fourth (1/4) of an inch in size. It shall be dry and free from dust and dirt. In cold weather it must be heated immediately before using.
Not less than three hundred (300) pounds of Slag or four hundred (400) pounds of Gravel shall be used per one hundred square feet.
The materials shall be used as follows:
First lay one thickness of Rosin Sized Sheathing Paper or Unsaturated Felt (A), lapping each sheet one inch over the preceding one, and nailing only so often as may be necessary to hold in place until covered with the Tarred Felt (B), and the nailing may be omitted entirely if practicable.
Over the Rosin Sized Sheathing or Unsaturated Felt lay two (2) full thicknesses of Tarred Felt (B), lapping each sheet seventeen (17) inches over the preceding one, and nailing along the exposed edges of the sheets only so often as may be necessary to hold the sheets in place until the remaining Felt can be applied.
Over the entire surface of the Felt thus laid, spread a uniform coating of Pitch (C), mopped on. Then lay three (3) full thicknesses of Felt (D), lapping each sheet twenty-two (22) inches over the preceding one, and nailing, as laid, every three (3) feet, not more than ten (10) inches from the upper edge.
When the felt is thus laid and secured mop back with pitch (E) the full width of twenty-two (22) inches under each lap. Then spread over the entire surface of the roof a uniform coating of Pitch, into which, while hot, embed Gravel (F).
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