Stepping Stones

A landscaper’s approach to building a flagstone path that looks (and feels) like a nature-made trail.

A natural stone walkway is meant to be rugged, rustic and rough in surface and style, yet comfortable to travel. Unlike a formal landscape, which calls for precision and uniformity, casual settings are suited for a flagstone path that looks like it has been there for decades, as if it floated in on a stream of gravel.

Such natural beauty doesn’t always happen naturally; it sometimes takes calculated action to achieve a spontaneous-looking result. (Constructing a durable and stable walkway always requires calculated action.) That’s why we consulted Scott Reynolds of Creative Habitats Inc. in Minnetonka, Minnesota, who shared his tricks and techniques for forming an uncontrived-looking path.

Prep steps
Before deciding to use natural flagstone, it’s important to consider whether this textured surface works for your needs. Scott cautions that flagstone may not be ideal for heavy-traffic areas, especially if they will be used by young children or elderly adults, because it can be a tripping hazard. Comfort and safety are essential concerns. Also keep in mind whether you’ll need to clear snow from the path during the winter. If so, a walkway constructed of manufactured pavers or concrete may be a better option.

Flagstone is a category of large sedimentary rocks including sandstone, limestone, bluestone and Chilton (native to Wisconsin). The types you find may depend on the region where you live. Prices are based on weight and are typically lower if you choose a stone that is native to your area. Flagstones range from 1/2 to 3 in. thick. They are available in irregular shapes (the type used in this project) and in cut form (usually rectangular shapes).

For a path or patio, 1-1/2- to 2-in.-thick stones are best. Thinner stones are more prone to breaking (during and after installation); thicker ones are heavier to lift and require that you remove more soil when setting them.

On average, the flagstones sold for making a path are about 18 x 18 in., which would cover 2-1/4 sq. ft. Depending on the stones’ thickness and density, Scott estimates that each ton will cover about 80 sq. ft. The smaller sizes (9 to 14 in. across) are called steppers. Although they are easier to lift and maneuver, steppers are not as stable as the heavier, larger flagstones (which can be 18 to 36 in. across). The optimum-size stepping stone for a comfortable walk is 18 to 24 in. across.

Scott sets the stones on a 2-in.-thick base of sand. At that depth, each cubic yard of sand covers 162 sq. ft. (the space for about 72 average-size stones) so Scott orders 1 cu. yd. of sand for each ton of stone. If your soil is all sand (rather than peat or clay), you can use less sand, but you’ll need to have some extra for filling low spots.

In any landscaping project you should try not to disturb tree roots (many of which are just below the soil’s surface). But if that is unavoidable, Scott recommends trimming back any affected trees before you dig. And of course, you must always dial 8-1-1 to have utilities marked before excavating, even for shallow digging.

Design steps
Whether you want a pathway to lead from your driveway to a door or to wind through a flower garden, start by mapping the path outlines with a heavy rope or garden house. This allows you to visualize and easily tweak the shape. For a natural result, let the pathway meander: No straight lines, Scott says. He also recommends shaping the entry points to be wider than any other parts of the path and designing the stretch between the ends with varying widths.

Once you’ve established an outline, lay out the stones for the entire path before installing the first stone. Fit the shapes together “mosaic style” so the gaps between them are somewhat consistent in width. “One stone has to have a relationship to the next: in shape, elevation and spacing,” says Scott. Then take a walk on the path from both directions to see if the stride is comfortable.

Setting oddly shaped stones for a path or patio is like fitting a puzzle together. Try to match curves and angles with neighboring stones, and keep the gaps about 4 to 6 in. wide.

Stones do not need to be set level with the horizon; they can flow up and down with gentle slopes. But where there are strong elevation changes, you should form stone steps. Make each tread level (horizontal) and shape the front edge of the step (the nosing) to be somewhat curved (shape with a chisel, if needed); the back edge of the step tread can be straight.

Installation steps
Leaving all of the stones in place, Scott begins by setting the stones at the two ends of the path. He marks the outline of the stone’s shape with the tip of a spade and then lifts the stone back to remove soil and debris and to add a sand bed. The beginning and ending stone heights should match the ground level of the approach edge. From there, Scott works toward the midpoint of the path, adjusting stone angles and heights to eventually meet at a common elevation.

Press the tip of a straight-edge spade straight down along the edges of the stone to mark its outline. This “custom-shape” excavation saves work, enables you to remove less soil and allows you to see how the stone fits in the pathway puzzle.

To adjust a stone’s position, tip the stone on edge and “walk” (or rock) it side-to-side; then slowly lower it all the way to the ground. Flagstones are rock hard, but they can easily crack and break.

Add or remove sand beneath each stone to adjust its height and angle. Pack sand under the edges with your fingers or a mallet to be certain that the entire stone is well supported.

It’s important that the stones be set on stable (undisturbed) soil, so Scott warns not to dig into the established soil any farther than necessary. Because the stones vary in thickness, you’ll need to scrape down the soil for each stone accordingly, allowing for the 2-in. sand base. The overall goal is for the tops of the stones’ edges to be flush from one stone to the next.

A straightedge (not a level) is used to check heights of adjacent stones. The path (and each stone in it) can be set with different slopes and angles; it’s only necessary that the top surfaces meet at even heights.

As you prepare the bed for each stone, be sure to remove grass, roots, pinecones, leaves and any other organic matter that could decompose and leave voids. If you encounter a rock poking above the soil’s surface, remove it; then fill the hole with soil and firmly compact it before laying the sand base. After setting each stone, step and stomp on each part of it to be sure that it is rock-solid in its new, natural home.

A flagstone path offers many options for filling the spaces between stones. For a comfortable and safe walkway, you need to build the infill up to the same elevation as the tops of the stones – like grout between tiles.

You can fill the gaps with planting soil and groundcover plantings or grass. Scott prefers grass or some type of hardy groundcover such as moss or a low-growing native perennial. He packs soil in the gaps and adds seed or plantings, which spread to cover the soil. To set a flagstone path across an established lawn, he simply outlines each stone’s shape with a spade; then he removes the sod and 3 to 4 in. of soil (depending on the thickness of the stone), smoothes down 2 in. of sand and settles the stone in position until it’s solid and level with the ground. Future care is as simple as running the mower right over the path — no trimming required.

Another option is to fill the gaps with loose material such as mulch or pea gravel. However, loose material is less than ideal because the bits never stay in place; they wander onto the surrounding lawn or park on top of the stones, making the path uncomfortable or even dangerous to walk on. Loose materials also settle or decompose and need to be “topped off” once in a while. On the other hand, they do not need to be kept alive. You can choose which type of maintenance you’d rather perform.

This project is part of HANDY's Top 5 Collection: Outdoor Projects.
Click here to check out the other four outdoor projects in this collection.