How you attach the stair stringers to the top of the deck and to any landings will be critical. You should reinforce the rim behind the stairs to provide a solid base for attachment. Use positive connections to install stair stringers using stair stringer connectors to the front face of the rim to provide adequate support.
If your first tread steps down from the deck you must extend the rim joist to create a solid surface below the deck rim to attach to. You should attach 2x6 or 2x8 support framing under the rim flush to the bottom of the stringer.
Install a piece of blocking below the rim joist to extend the attachment surface for your stairs stringers.
Measure down from the top of the deck and mark the top of your stair stringers with a level. Example: Because each stair will be 6-3/8" finished height we will measure down 7-3/8" to compensate for the missing stair tread.
Mark the location for each stair stringer. Most wood stairs use 16" on center. Follow manufacturer's guidelines for composite decking. Most composite decking materials require 12" or even 10" on center spacing.
Bend your stair stringer connectors to the correct angle. Hold the connector under the stringer and raise the stringer to the proper height. Then mark the height of the connector. Repeat for each stringer attachment. Use 10d - 1.5" hot dipped galvanized nails.
Nail the stair stringer connectors into place then nail the 2x12 stair stringers to the connector side flange and bottom.
