How to Hang Stairs on a Deck

Use a square and pencil and make vertical marks on the outer rim joist of the deck where the stairs will be mounted to indicate the position of the stair stringers. Note that to have stairs with a greater weight-carrying capacity, stringers should be mounted every 16 inches on center.

Hold the upper end of one of the stair stringers -- available pre-cut from home centers and lumber yards -- in position on one of the vertical lines. Drive 3-inch galvanized deck screws through the back of the rim joist and into the vertical edge of the stringer with a power drill that has a Phillips head attachment installed. Attach the remaining stringers to the rim joist in the same manner.

Measure the distance in between the stringers at the rim joist with a tape measure. Cut a length of 2-by-6 lumber to this length with a circular saw to make a cleat. Hold the cleat to the rim joist directly in between the stringers. Ensure the top edge of the cleat is flush with the top edge of the stringers. Screw the cleat into the rim joist with 3-inch deck screws. Install more screws from the sides of the stringers and into the edge of the cleat. If you have more than two stringers, cut cleats for the spaces between them and install those cleats in the same manner.

Determine the width for the stair treads by measuring from the outside edges of the two outermost stringers. Add 2 inches to this measurement to allow for an inch of overhang on each side. Cut as many stair treads as needed at this width from 2-by-12 lumber, using a circular saw.

Place the treads in position on the horizontal surfaces across all of the stringers. Ensure that there is equal overhang on each side of the treads. Secure the treads to the stringers with 3-inch deck screws.