How to Build Interlocking Stone Steps

Design the steps. Lay out the line they will follow, straight or curved, and measure the degree of slope to calculate how many steps will be needed, what size they will have to be and how much material they will require. Determine the slope by putting a stake at the top of the stair point and a pole or tall stake at the bottom. Tie a string between the bottom of the stake and the pole. Level the string with a line level and measure the distance from the bottom of the pole to the string. That measurement and the distance determine the slope -- a drop of 1 foot in 3, for instance, is a 33 percent grade.

Figure the number of steps needed by the distance to be covered. Step treads (the tops) should be at least 1 foot. Risers (the vertical elements) should be no more than a foot. In the example, a 33 percent grade would require 3 steps, each with a 1-foot tread and 1-foot riser. Adjust the design to the slope. Use wider treads and shorter risers (but at least 6 inches) for gentler slopes. Plan steps to be at least 5 feet wide.

Take those measurements to a building supply store or masonry outlet and pick out a style of interlocking stone. Calculate the number of stones needed (or have the store do it) based on the size of stone and the length and width of the steps. Buy extras to allow for breakage and other problems. Get special edging blocks or strips if needed so steps can be laid with even edges without cutting stones to fit.

Mark the length and width of the steps with wooden stakes and builder's twine, on both sides, spaced evenly. Excavate the step area with a shovel, to at least twice the depth of the stones and in a general stair step way; essentially dig steps into the dirt. Allow for at least a 6-inch base under the stones. Make the excavation deeper if the ground has poor drainage or is not firm.

Fill the step area with 4 to 6 inches of medium gravel and compact it firmly with a hand tamper. Use boards for temporary restraints to hold the gravel on steep slopes; secure them with stakes outside the step width. Add an inch or two of sand to make it easier to adjust stones for level. The sand level should reach the bottom of an interlocking stone flush with the ground outside.

Lay the stones, starting at the bottom, according to the design of the interlocking pavers. Make a straight edge across the front of the first step and fill the tread with stones to the next riser. Remove the board, if there is one, and secure the gravel behind with the last stone on that step. Move up to the next step and repeat the process. Continue up the slope until all steps are set and secure. Level each stone and tap it firmly into place with a rubber mallet. Overlap the first stone in the second tread over the last stone below; generally that will involve placing a straight edge over an interlocking edge.

Secure the stones with mason's sand or polymeric sand, unless the interlocking steps fasten without sand joints. Sweep sand with a broom into gaps between the stones and dampen it with a garden hose mister to secure it (this may take several applications, as sand seeps down into the joints).