If you have an attic mounted heating and/or cooling system, there are such minimum requirement that allow the repair, removal and replacement parts to be easily accessed.

Your building dept. or an HVAC contractor can tell you those requirements for your area.

Home Depot sells the Werner compact attic ladder, which may be what you want to use if you downsize the opening. Its access is not as good as standard pull-down stairs, but it should be adequate for most uses. It works more like an extension ladder than stairs. We installed one in our house because there were no attic stairs and we got tired of hauling a ladder into the house to get up into the attic.

Bruce

In my area, yes, there is a minimum size requirement. I don't recall what it was though because we had to go larger to accommodate our hvac unit.

2009 IRC:

SECTION R807 ATTIC ACCESS

"R807.1 Attic access. Buildings with combustible ceiling or roof construction shall have an attic access opening to attic areas that exceed 30 square feet (2.8 m2) and have a vertical height of 30 inches (762 mm) or greater. The vertical height shall be measured from the top of the ceiling framing members to the underside of the roof framing members.

The rough-framed opening shall not be less than 22 inches by 30 inches (559 mm by 762 mm) and shall be located in a hallway or other readily accessible location. When located in a wall, the opening shall be a minimum of 22 inches wide by 30 inches high. When the access is located in a ceiling, minimum unobstructed headroom in the attic space shall be 30 inches (762 mm) at some point above the access measured vertically from the bottom of ceiling framing members. See Section M1305.1.3 for access requirements where mechanical equipment is located in attics."