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Ventilation openings through foundation walls shall be provided. The openings shall be placed so as to provide cross ventilation of the under-floor space. The net area of ventilation openings shall be in accordance with Section 1202.4.1.1 or 1202.4.1.2. 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 not greater than 1/8 inch (3.2 mm).
  7. Operable louvres, where ventilation is provided in accordance with Section 1202.4.1.2.
1202.4.1.1 Ventilation Area for Crawl Spaces With Open Earth Floors
The net area of ventilation openings for crawl spaces with uncovered earth floors shall be not less than 1 square foot for each 150 square feet (0.67 m2for each 100 m2) of crawl space area.
1202.4.1.2 Ventilation Area for Crawl Spaces With Covered Floors
The net area of ventilation openings for crawl spaces with the ground surface covered with a Class I vapor retarder shall be not less than 1 square foot for each 1,500 square feet (0.67 m2 for each 1000 m2) of crawl space area.

Related Code Sections

1202.4.1 Interior Environment, Ventilation Openings
Ventilation openings through foundation walls shall be provided. The openings shall be placed so as to provide cross ventilation of the under-floor ...
1202.4.1 Interior Environment, Ventilation Openings
Ventilation openings through foundation walls shall be provided. The openings shall be placed so as to provide cross ventilation of the under-floor ...