1523.05   SLATE ROOFING.
   (a)   Quality and Exposure. Slate shingles shall be free from knots or knurls and not less than three- sixteenths of an inch thick. The maximum exposure to the weather shall be one-half the length of the slate minus one and one-half inches.
   (b)   Underlay. Before laying slate, the roof sheathing shall be covered with an underlay of asphalt- saturated felt weighing not less than thirty pounds per square.
(Ord. 213-60. Passed 11-21-60.)