Minimum vertical height of 30 inches measured from the top of the ceiling framing members to the bottom of the roof framing members.
Attic access hatch minimum size.
An attic access opening runs between the ceiling joists whenever possible.
For smaller attic openings with a minimum measurement of 18 x 24 you will need to measure the swing clearance inside the attic space.
These specs are per r807 1 of the international residential code irc and the residential edition of the florida building code fbc.
If the access is located in the ceiling the minimum unobstructed headrom above the opening must be 30 inches measured vertically at some point over the access.
If the attic space is smaller than these specs then an access hatch is not required.
The access opening should be located in a hallway or other readily accessible location and minimum 22 x 30.
The compact attic ladder requires a minimum height of 28 and minimum depth of 44 inside the attic above and behind the opening.
The 2007 california building code requires a minimum attic access opening of 20 inches by 30.