Step 1 Finish Decking First
Install and trim the decking before starting the installation of the stairs. Lay out and pour any footings needed for the landing platform and install the landing pad. Compute the rise and run of both sections of the stairs. Build the landing platform using the same techniques you would use for a deck (the platform is, in fact, a miniature deck). Install and plumb the posts, build the perimeter frame, hang joists in joint hangers, and attach the decking-with the same orientation and pattern as the deck, if possible.