How to Build Wooden Deck Stairs

If you are going to build stairs for a wooden deck, be prepared to engage in some highly important calculations and measurements. Because the deck stairs can go wildly wrong if you don't measure accurately, it is vitally important to take that step seriously. But after the measurements are in place, building deck stairs is simply a case of following directions.

Things You'll Need

• 2-by-4s
• 4-by-4s
• 2 2-by-12s
• Tape measure
• Pencil
• Level
• Post-hole digger
• Circular saw
• Hammer
• Ratchet wrench
• Silicone caulk
• Gravel
• Framing square
• Metal cleats
• Plumbing bob

Instructions

1. Determine the number of steps needed for the deck stairs by taking the measurement of the vertical drop from the surface of the deck and dividing it by seven. Round off to the nearest whole number. Divide the vertical drop by the number of steps to determine the step rise figure.

2. Use the above calculations to lay out the stairs and determine the position of the posts. Position the posts 18 inches from the end of the span of the stairway. Place a straight 2-by-4 on the deck and make sure it is level and square to the side of the deck. Use a plumbing bob to mark the point of the ground at the center point of the footing.

3. Dig the post holes and pour gravel footing into the holes to secure them. Attach metal posts to the footing and then install 4-by-4 posts into the holes. Taking these steps ensures solidity of the posts even when the soil grows damp.

4. Mark the rise measurement on one leg of the framing square with a piece of tape, and mark the run measurement on the other leg. Lay out the two 2-by-12 stair stringers by beginning at one end and positioning the square with tape marks that are placed flush to the edge of the board. Outline the rise and run for each individual step, and then use the pencil to draw in the tread outline against the bottom of each of the run lines. Trim the ends of the stringers with a circular saw.

5. Attach metal cleats so that they are flush with the bottom of the tread outlines using screws. To keep the screws from splitting the wood, first drill 1/8-inch pilot holes. Use 1 1/4-inch joist nails to attach angle brackets to the upper end of the stringers. The brackets need to be flush with the cut ends of the stringers.

6. Align the top point of the stringer so that it is flush with the surface of the deck. Use 1 1/4-inch joist nails to attach the stringers by nailing the brackets to the deck. Drill pilot holes through each of the stringers and the posts that are adjacent to them. Each of the holes should be counter-bored to a depth of 1/2 inch; this can be accomplished using a 1-inch spade bit. Use screws and washers to attach the stringers to the posts, and then seal the screw heads with silicone caulk.

7. Measure the width of the stair treads, and then cut two 2-by-6 boards for each tread. Each step will require positioning the front 2-by-6 on the cleat. The front edge should be flush with the tread outline on the stringers. Drill a 1/8-inch hole before attaching the front 2-by-6 boards to the cleats with screws. Finally, position the rear 2-by-6 boards on the treat cleats. Make sure there is just enough space between the boards that a small nail head can fit between them. Drill pilot holes, and attach to the cleats with screws.