R905.6 Slate and Slate-Type Shingles
Exception: Detached accessory structures that contain no conditioned floor area.
Underlayment installed where the basic wind speed equals or exceeds 120 mph (54 m/s) shall comply with ASTM D 226 Type II or ASTM D 4869 Type IV. The underlayment shall be attached in a grid pattern of 12 inches (305 mm) between side laps with a 6-inch (152 mm) spacing at the side laps. Underlayment shall be applied in accordance with Section R905.2.7 except all laps shall be a minimum of 4 inches (102 mm). Underlayment shall be attached using metal or plastic cap nails with a head diameter of not less than 1 inch (25.4 mm) with a thickness of at least 32-gauge sheet metal. The cap-nail shank shall be a minimum of 12 gauge (0.105 inches) with a length to penetrate through the roof sheathing or a minimum of 3/4 inch (19 mm) into the roof sheathing.
Exception: As an alternative, adhered underlayment complying with ASTM D 1970 shall be permitted.
|4:12 ≤ slope < 8:12||4|
|8:12 ≤ slope < 20:12||3|
|Slope ≤ 20:12||2|