(a) Quality of Materials. Materials used in the construction of built-up roofing shall comply with the requirements of Underwriters Laboratories, Inc., and American Society for Testing Materials (ASTM) standard and tentative specifications D 226-60, D 227-56, D 250-62T or D 655-62T.
(b) Plies or Layers. The covering shall include at least three layers applied in a manner approved by the Building Commissioner. Each ply of felt shall have a minimum weight of thirteen pounds per square.
(c) Stone or Gravel Surface. Unless otherwise provided in this Building Code or approved by the Building Commissioner, built-up roofs shall be surfaced with roofing gravel or crushed stone at the rate of 400 pounds per square for slopes not more than one in twelve and the rate of application shall be decreased proportionately to 275 pounds per square for slopes of three in twelve. If crushed slag is used, it shall be applied at the rate of approximately 300 pounds per square for all slopes.
(d) Asphalt-Granule Cap Sheet. The top ply of felt and crushed stone or slag surfaces may be replaced with one layer of mineral-surfaced asphalt can sheet weighing not less than eighty-five pounds per square and meeting the requirements of ASTM D 371-58.
(Ord. 213-60. Passed 11-21-60.)