How to Build a Wood Staircase With a Small Deck at a 90 Degree Angle

Layout

Step 1

Measure your deck from the ground to the top of the deck. Divide this by eight to get the number of steps required. Divide this number by two. Multiply the answer by 10 inches. Measure out from the deck this distance to find where the foot of the top stair will end.

Step 2

Mark your landing deck with a wooden stake in each corner. Make the edge nearest the main deck 10 inches closer to the deck than the end of the stair. Make your deck at least 3 feet long and a little wider than your stairs.

Step 3

Find the 10-inch mark on the short side of your framing square and wrap a string around it. Find the 8-inch mark on the long end and stretch the string across to it and wrap it around, tying it snug.

Step 4

Lay the square on a 2-by-10 board, with the string matched to one edge and the corner of the square on the board. Trace the corner of the square to mark one step. Shift the square until the string on the short side matches up to the end of the line from the long side and trace again. Repeat for each step. These are stringers; mark four of them.

Step 5

Use the square to mark a 90 degree line down across the board from the bottom line you traced from the short side of the square, and another from the top line you traced from the long side of the square. Do this to each stringer and cut them to length on those lines.

Stairs

Step 1

Cut the notches you traced with a jig saw. Cut one 2-by-10 and one 2-by-8 for each step as long as you want your stairs to be wide using a circular saw. They must be a minimum of 24 inches wide.

Step 2

Lay the stringers out in two pairs, parallel to each other, with the points of the notches facing up. Screw one 2-by-8 between each pair of stringers on each 8-inch face using 3-inch treated deck screws, two for each piece, using a cordless drill.

Step 3

Add a 2-by-10 on top of each 2-by-8, so that the outside edge of the 2-by-10 is flush with the face of the 2-by-8. Screw them to the stringer as well, with two 3-inch treated deck screws in each end of each piece.

Installation

Step 1

Dig a 24-inch-deep post hole in place of each stake. Stand a 4-by-4 treated post in each hole. Cut two 2-by-8s to the width, and two 3 inches shorter than the length of your landing deck. Bolt them to the posts with 3-inch lag bolts at the proper height, to create a rectangle frame. Drill a 1/4 inch hole for each bolt. Drive them in with a socket wrench.

Step 2

Add a 2-by-8 between the side boards, every 12 inches, with 3-inch treated deck screws through the outside boards into their ends. Use two screws in each end. Cut 5/4-by-6 treated deck boards as long as your platform. Cut the posts off flush with the edge boards using a reciprocating saw. Screw the deck boards to the top of the platform.

Step 3

Drill 1/4 inch holes through the edge boards of the top and bottom platforms where the stringers meet them. Attach the stringers with lag bolts through these holes from the inside into the back of each stringer.