1507.17.4.1 High wind attachment.
BC § 1507.17.4.1
Underlayment applied in areas subject to high winds (V asd greater than 110 mph (49.1 m/s) as determined in accordance with Section 1609.3.1) shall be applied with corrosion-resistant fasteners in accordance with the manufacturer's instructions. Fasteners shall be applied along the overlap at not more than 36 inches (914.4 mm) on center. Underlayment installed where V asd is not less than 120 mph (53.6 m/s) shall comply with ASTM D 226, Type II, ASTM D 4869, Type IV or ASTM D 6757. The underlayment shall be attached in a grid pattern of 12 inches (304.8 mm) between side laps with a 6-inch (152.4 mm) spacing at the side laps. Underlayment shall be applied in accordance with Section 1507.2.8 except all laps shall be a minimum of 4 inches (101.6 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 not less than 32-gage (0.0134 inch (0.34 mm)) sheet metal. The cap nail shank shall be a minimum of 12 gage (0.105 inch (2.67 mm)) with a length to penetrate through the roof sheathing or a minimum of 3/4 inch (19.1 mm) into the roof sheathing. Exception: As an alternative, adhered underlayment complying with ASTM D 1970 shall be permitted.
