How to Install Flagstone Steps

Measure the height and width of each step. Order the stone and have it pre-cut by a mason. Also order the risers and cut them with a wet saw or have the mason cut them as well. The risers must cover all faces of the step.

Arrange the stone steps in succession beginning with the tallest and working your way to the shortest. If you are stacking stones, begin with the base steps and add a layer of mortar before stacking the next step.

Arrange the flagstone risers on the step. Step back and inspect the arrangement to ensure it is the intended design. It will not be exact because the stone will not be properly spaced, but it will show the general arrangement.

Apply a thin layer of mortar to the sides of the step. Lay the vertical risers in the desired pattern. Push plastic spacers between the flat stones to create even spacing throughout the step. Place a wood block against the stone and tap it with a hammer to help it bind with the mortar.

Spread a thin layer of mortar on the top of the steps and lay the stone to fit with the desired look. Use plastic spacers to even the stones and use a wood block and hammer to tamp the stones in place.

Allow the mortar to dry. Either fill the gaps with sand or fill the gaps with mortar. Use a trowel to flatten the mortar. Use the edge of the trowel to scrape the mortar even with the stone. Allow the mortar to dry.