// CODE SNIPPET
1203.4.1 Openings for Under-Floor Ventilation
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The net area of ventilation openings shall be not less than 1 square foot for each 150 square feet (0.67 m2 for each 100 m2) 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):
- Perforated sheet metal plates not less than 0.070 inch (1.8 mm) thick.
- Expanded sheet metal plates not less than 0.047 inch (1.2 mm) thick.
- Cast-iron grilles or gratings.
- Extruded load-bearing vents.
- Hardware cloth of 0.035-inch (0.89 mm) wire or heavier.
- Corrosion-resistant wire mesh, with the least dimension not greater than 1/8 inch (3.2 mm).