Check to make sure that the attic area in which you intend to install the stairway is strong enough for walking and working on and has adequate headroom .
Position the opening for the stairway . Measure to be sure there is enough clearance for the stair as it swings to its full length ( Fig . 1 ). Use the Specification Chart on the first page to determine the proper clearance for the projection and landing space . Be sure there is enough space for a safe landing area when the stairway is open .
Making & Framing the Rough Opening I
Locate all electrical wiring in the vicinity of the stairway installation area , and avoid contact with it during all phases of installation .
Cut the rough opening through the ceiling material according to the size shown on the stairway carton .
✎ The rough opening size of the stair , as listed on the carton , will be approximately 1 / 2 " wider and longer than the actual net size of the stairway . This allows room for shimming and squaring the stairway in the opening .
✎ Installation parallel to existing joists normally requires a frame with single headers . Installation perpendicular to the existing joist requires a frame with double headers . If your home uses roof trusses , do not cut ceiling joists without engineering consultation and approval .
✎ If the folding attic ladder is wider than the spacing between the ceiling joists , you should consult a structural engineer before installing , since cutting into a ceiling joist could weaken the structural integrity of your ceiling .
If joists must be cut , stabilize them by nailing 2 joist-size stabilization boards perpendicular to the ceiling joists before cutting .
Using joist-size material , build a four-sided frame to install the stairway . Shaded areas in Fig . 2 & 3 illustrate the frame that must be built before installing the stairway . When making double headers ( for perpendicular installation ) fasten members together with 10d common nails . The double joist sections shown in Fig . 3 must be long enough to be supported by a load bearing wall at both ends .