How to Construct Stairs with Interlocking Blocks

Dig a 9-inch deep square hole that has the total dimensions of the stairway base. Rake the area, or bed, to level the soil. Fill the bed with a 6-inch layer of crushed rocks. Compact the rock layer with a tamper or compacter. Top the rock layer with a 1-inch deep layer of sand. Compact the sand layer with the tamper or compacter.

Line the bottom of the bed with interlocking blocks. Place a level across the blocks to check for evenness, and remove or add gravel beneath as needed to make the blocks level.

Fill the cavities in and around the blocks with crushed rocks. Tamp the layer. Sweep the crushed rocks from the top edges of the blocks, and then place beads of concrete adhesive along the blocks' top edges.

Place a course of interlocking blocks on top of the first layer of blocks, reducing the second layer's dimensions to account for the first stair step. Push the second layer of blocks into the concrete adhesive. Fill the cavities with crushed rocks. Sweep the crushed rocks from the top of the blocks, and apply adhesive to the block tops.

Add courses of interlocking blocks in the same manner up to the top step. An option for some interlocking block styles is to drive stakes through the layers of blocks with a 10-pound hammer or sledge hammer.

Add capstones to the block tops to finish the stair steps. Sweep sand into all joints between the blocks and capstones.