To make a flagstone path as durable and solid beneath your feet as it appears to your eyes, each stone needs firm footing on a well-drained base. Base preparation is even more critical where the soil freezes in winter or where the soil is high in clay. On ground that slopes more than a foot every 10 feet, you may want to consider putting in steps in conjunction with the path. Flagstone paving can be made from any type of horizontally layered rock that can be split into flat slabs, or flags. Arizona sandstone, Pennsylvania bluestone, and slate are among such rocks. Artificial flagstone may be made of concrete, cast into slabs, and dyed the yellow, buff, tawny-red, or gray color of natural stone. In any case, use one-to-two inch thick flagstone for paving. Irregularly shaped flags lend a casual air to a path, while square and rectangular flags create a sense of order and formality.
- PLANNING THE PATH In planning a path, consider its purpose. Jogs or curves slow footsteps and might be what is needed where you want to encourage a prolonged look at a choice planting. Where footsteps will be hurried, such as from the back door to the vegetable garden, lay out a straight path. Bear in mind that two people strolling together along a major garden path—even two intimate people—need paths four to five feet wide. Eighteen inches is adequate for a small, secondary path for one person. Sprinkle pulverized limestone on the ground to outline the proposed path. For a straight path, guide yourself with strings and stakes. To achieve smooth bends on a curved path, use two garden hoses to mark the edges, and measure across at intervals to keep the path’s width constant.
- DIGGING OUT THE SOIL Remove existing soil to a depth of at least four inches. If the site is soggy (especially in winter), allow for more drainage by digging out more soil, up to 12 inches if necessary. You won’t need the excavated soil, so shovel it directly into a wheelbarrow. Sprinkle this excess soil between the layers of a compost pile, or stockpile it for use in potting mixes.
- ESTABLISHING A BASE Shovel porous drainage material such as coarse sand or stone dust into the excavated area, tamping and smoothing it with a board as you proceed. This material will provide a solid base for the path and prevent water from collecting and freezing beneath the flagstones.
- Fill in with enough drainage material so that the topsides of the stones will be a half-inch above ground level after they’re set in place. Make the center or one side of the path an inch higher than the rest so that surface water will run off.