Building steps into a hillside requires some planning but the construction is simple, according to CreativeHomeowner.com. When designing your steps, consider the amount of traffic. Plan for steps that are 1.5 to 1.8 metres (5 to 6 feet) wide if you want to allow two people to walk on them side-by-side, or 1.2 metres (4 feet) wide for a single person. Landscape designers suggest a 40 cm (15-inch) depth, or run, for the treads and a 15 cm (6 inches) step height, or rise, between each step.
Measure the rise and run of the hillside where you'll be building the steps. Divide the hillside's rise in centimetres (inches) by fifteen (six) to determine the number of steps you will need. Round the result to the nearest whole number. Divide the run in centimetres (inches) by the number of steps to determine the size of the treads. Ideally, your steps will be between 33 and 38 cm (13 and 15 inches) wide. Purchase pressure treated lumber with the height of the determined rise and at least 10 cm (4 inches) wide.
Drive one stake in each of the corners of the stairway. Run string tightly from one stake to another to create the outline of the path of steps and to act as a guideline.
Dig a shallow trench at the bottom of the stairs for the first riser. The trench should be just deep and wide enough in order for the pressure-treated lumber to be able to sit securely in the ground. Dig trenches for the first riser's side timbers to 15 cm (6 inches) past the tread depth. The trenches will get deeper as you dig into the hillside. Ensure that the bottoms of the trenches remain level.
Measure and cut the front and side risers to length. The side risers should be the length of the tread, plus 15 cm (6 inches), minus the width of the front riser. Bore a 0.75 cm (1/2-inch) hole on each end of each riser, centred 6.25 cm (2 1/2 inches) from the ends. Place the risers in the trenches and level them with additional soil as needed. Drive an 45 cm (18-inch) length of rebar through each of the pre-drilled holes and into the ground to anchor the step. Dig out the soil between the timbers to create a level surface between the sides of the step.
Cut the front riser to the same length as the first stair for the second step and drill a pilot hole centred 6.25 cm (2 1/2 inches) from each end. Place the front face of the second riser 15 cm (6 inches) from the ends of the side risers below, lining up the drilled holes. Drive a 30 cm (12-inch) galvanised spike through each of the pre-drilled holes to anchor the new step to the one below.
Dig a shallow trench for each of the second step's side risers level with the tops of the first step's sides. Measure and cut the side risers to the same length as those for the first step. On the end of each side riser that will overlap those of the first step, drill a pilot hole. Position the side risers, level, and drive a 30 cm (12-inch) galvanised spike through the pilot holes into the risers below. Dig out the soil between the timbers to create a level surface between the sides of the step, as before.
Repeat Steps 5 and 6 for the remaining steps. Cut the side risers for the top step 15 inches (6 inches) shorter than the ones below. Measure and cut lumber for a back riser for the top step. The riser should fit between the two side risers. Anchor the riser with 45 cm (18-inch) rebar as in Step 4. Remove the stakes and string guidelines.
Pour and tamp down gravel in the trench between each step to create a two-inch bed. Pour and tamp down sand over the gravel until you reach a height where the brick or stone of your choice lies flush with the top edges of the risers. Level the sand.
Arrange bricks or stones in the sand, leaving 15 mm to 30 mm (1/16-inch to 1/8-inch) joints between each piece. Tap the bricks into place and level as needed. Spread a thin layer of mason's sand over the bricks. Sweep the sand in all directions to fill in every crack. Spray the surface lightly with water to wash off extra sand from the surface and to pack the sand. Allow the sand to dry. Sand and spray as needed until the joints between the bricks are all filled and compacted.
Check if your town requires a permit to build steps into a hillside. Some areas are regulated due to erosion issues.