The measurements should be within 1 8 inch to be considered square see figure 13.
How to frame an attic access opening.
Build a box to frame the opening with lumber boards the same depth as floor joists.
To solve this consider installing a frame around your attic door.
Nail this framing into place around the perimeter of the attic access opening.
The access door also serves as a ceiling vent for removing fumes from the room to.
If your ceiling joists are spaced so that they make up the other two sides of the rough opening check the opening for squareness by measuring across the diagonals.
If you are installing a pull down set of stairs follow instructions that came with the unit.
The frame for the rough opening requires four sides.
This diy home improvement project will make your attic stairs fit nice and square.
The headers make up two of those sides.