How-to-frame-attic-stairs, attach temporary support boards at least 4 inches wider than opening using a drill and 3" deck screws. fasten the boards to a dimensional spread to hold the frame of the new ladder on the short side without impeding the ability to open the door.. This is the end wall of the attic above my garage. the space is 12-feet wide and ceiling height is 8 feet. i didn't build this house, but the architect did everyone a favor by making the vast space above the 40-foot-long garage out of attic trusses.