Minimum Crawl Space Height

There must be at least 18 inch clearance between floor joists and surface of the ground.
Minimum crawl space height. Wood joists or the bottom of a wood structural floor when closer than 18 inches 457 mm or wood girders when closer than 12 inches 305 mm to the exposed ground in crawl spaces or unexcavated area located within the periphery of the building foundation. Access openings to a crawl space through the floor shall be a minimum of 18 inches by 24 inches. Ground level must be at least 18 inches below bottom of wood floor joists and 12 inches below bottom of chassis beam. 2015 international residential code irc section r408 4.
This seems to me to indicate that the minimum floor to underside of joist minimum height must also be at least 24 high. Crawl space openings through a perimeter wall shall be not less than 16 inches by 24 inches. Minimum height debris wood rot the crawl space must be free of debris. The entire crawl space should be free of debris.
Access door to the crawl space must conform to specifications. For unvented crawl spaces it is best to place the openings in the floor to preserve the integrity of the insulated perimeter wall. In order to ensure ease of access to the crawl space any access door must be at least 18x24 inches source. Crawl space require ments basementless spaces a.
Access shall be provided to all under floor spaces openings through a perimeter wall shall be 16 inches by 24 inches 407mm x 610mm. Preservatives shall be listed in section 4 of awpa u1. Where it is necessary to pro vide access for maintenance and repair of me chanical equipment located in the under floor.