How to Build a Hillside Stairway

Planning

• Use landscaping paint to mark where you want to build your stairway. Begin to plan the dimensions of your steps at this stage as well. With a steep slope, you need to install more steps with a shorter run (the distance from front to back, horizontally). With a gradual slope, a smaller number of broader steps works well, as "Black & Decker: The Complete Outdoor Builder" points out. A 15-inch tread (a step's horizontal distance from front to back) with a 6-inch rise (the vertical distance from one tread to the next) are considered typical dimensions for a step on a moderate slope.

Measurements

• Measure the rise and run of your hillside. If it's a small hill, drive a tall stake into the ground at the bottom where your steps will begin, and drive another into the top where they'll end. Place a flat board from the bottom of the top stake to the top of the bottom stake, and measure the vertical distance from the ground at the bottom to the board. This tells you the slope's rise. Divide the rise by the thickness of your steps (their rise), estimating the result to the nearest whole number, to get the number of steps for your staircase. Measure the horizontal distance from the bottom of the top stake to the stake on the ground, using the board to keep your measurement straight. Divide this number by the total number of steps to determine the depth of the tread.

Creating the Foundation

• Excavate the ground where you'll place the stairs. Dig down to 12 inches at the site of each step, making the tread slightly broader since there will be some overlap. Place cinder blocks or crushed rock in the hole, and fill it with concrete. Dig several inches outward at the side of each step, digging down 2 to 3 inches, and insert an angled supporting stone in that space. Fill that space with concrete as well, and apply 2 inches of concrete over the top of the entire step. Let the concrete set for 24 hours after completing the process for each step.

Completing Installation

• The next day, add 1 inch of mortar above the concrete on the first step, which is the foundation for the rest of the stairway. Lay flat stones on top of it. Make sure they're level, and apply mortar between them as needed. After three days, apply mortar to the backs of your riser stones (the vertical ones between each step), and press them into place. Add mortar between the stones to fill any gaps. Follow the same process to add your treads (horizontal stones) and risers (vertical stones) for each step.