olid supports at top and bottom are essential to install wood stairs that will be attached to a boat dock. Attach a solid dock platform to a rock and then attach both your stairs and your floating or solid dock to this platform.
Step 1: Choose a Location for the Dock and Stairs
Choose a location with a large rock already in place to anchor the dock platform and stairs, or place a large granite rock, sized at least 3 feet long by 2 feet in width, and at least 12 inches high at the spot desired.
Step 2: Build a Dock Platform and Attach it to the Rock
Construct a dock platform to cover the rock base. Anchor the dock platform to the rock base with 10-inch rock bolts, nuts and washers. Install the rock bolts with a nut on the underside of the deck and a washer below the head. Tighten the bolts with the torque wrench to 150 foot-pounds. Attach the vertical sides of the dock platform.
Step 3: Measure for Stairs
Measure up from the dock platform to the edge of your deck for the stairs. Draw a plan to include landings where needed. Include stair handrails on your stairway. Measure the stairway width, which should be at least 36 inches.
Step 4: Measure and Cut Stair Stringers
Measure the rise and run of each section of the stairs to cut the stringers. If your height (rise) is 60 inches you will need at least 6 steps, but preferably 8 to 10. Each step must have a tread at least 10 inches deep, so your run (width of the staircase front to back) with 6 steps will also be 60 inches. With 10 steps, your run will be 100 inches. Work out your rise and run to match the slope of the staircase location. Draw the exact measurements of the stair stringers on 2x10-inch planks and cut a matched pair of stringers.
Step 5: Set and Fasten the Stringers in Place
Set the two stringers in place on the dock platform and secure them with 2-inch wood screws to the platform. Fasten the stringers to the top support of the stairs with wood screws.
Step 6: Add Risers and Treads
Cut risers from 2x6 planks and fasten them to the stair stringers with wood screws. Cut treads from 2x6 planks and screw them to the stair stringers on the run platforms. You will need 2 planks for each tread, and they should overhang each run by 1 inch, so cut down a 2x6 plank to 5 inches wide for the outer tread edge.
Step 7: Attach Handrails
Use 2x6 planks to make all parts of the handrails. Attach the handrail top so it extends to the edge of the lowest stair tread.