1203.4.1 Openings for under-floor ventilation.
BC § 1203.4.1
The net area of ventilation openings shall be not less than 1 square foot for each 150 square feet (304.8 mm 2 for each 45 720 mm 2 ) of crawl space area. Ventilation openings shall be covered for their height and width with any of the following materials, provided that the least dimension of the covering shall be not greater than 1/4 inch (6.4 mm): 1. Perforated sheet metal plates not less than 0.070 inch (1.8 mm) thick.
2.Expanded sheet metal plates not less than 0.047 inch (1.2 mm) thick.
3.Cast-iron grilles or gratings.
4.Extruded load-bearing vents.
5.Hardware cloth of 0.035 inch (0.89 mm) wire or heavier.
6.Corrosion-resistant wire mesh, with the least dimension greater than 1/8 inch (3.2 mm).
