Deck Stairs and Steps
Building stairs for a deck is usually considered the most difficult part of the project. It is probably a good idea to start by understanding the building code requirements for stairs. The minimum stair width is 36". The maximum stair rise is 7-3/4". The minimum tread depth is 10". The largest tread or riser height shall not exceed the smallest by more than 3/8". A minimum 3' x 3' landing area is required at the bottom of stairs. Flat ground may qualify. The maximum opening for an open riser is 4" for decks above 30". All exterior stairways shall be illuminated at the top and bottom landing. Stairs shall be provided with a minimum of 6'-8" headroom clearance.
You can watch an excellent video on decks.com about deck stair construction. The first step in building stairs is to measure the height of the stairs. Measure vertically from the top of the decking at the top of the stairs to the plane where the stairs will terminate. Input this measurement into decks.com stair calculator to determine the number of stairs and the rise and run of each step. The next step is to cut your stair stringers out of treated 2x12 material. Remember that the last step will need to be shorter the thickness of one deck board to create an equivalent step.
You can either attach your stringers to the inside or outside of the deck frame. Most stair stringers are spaced either 12" or 16" on center. Outside mounting is easier if you are using 2x10 framing for the deck frame. If you choose to install inside mounted stringers you will need to install blocking to attach the stringers to. For outside mounted stringers you will probably have to extend the rim joist by installing a cleat. This will provide a larger surface area to mount joist hangers.
The final step is to install the risers and treads. Most treads are composed of 2 courses of decking for each tread with a 1" nosing overhanging the riser board. Use two deck screws to secure the decking to each joist. Some composite decking materials are not approved for use on stairs. Reference each manufacturers installation instructions and ESR reports for more information.