315.3.4 Attic, Under-Floor and Concealed Spaces
Attic, under-floor and concealed spaces used for storage of combustible materials shall be protected on the storage side as required for 1-hour fire-resistance-rated construction. Openings shall be protected by assemblies that are self-closing and are of noncombustible construction or solid wood core not less than 13/4 inches (44.5 mm) in thickness. Storage shall not be placed on exposed joists.
- Areas protected by approved automatic sprinkler systems.
- Group R-3 and Group U occupancies.