Flagstone walkway before mortar is installed between the joints.
Build on a good foundation
As with many things in life, it's what's underneath the surface that's so important to a beautiful pathway. The base below the pieces of flagstone is what makes it sit level and firm in the ground, resistant to soil movement. Because we live in an area of hard clay soil, people often think they can just set pieces of flagstone on the surface of the soil to create their flagstone path. While this will work in the short term, once we get heavy rains or freeze/thaw cycles, that ground DOES move, and the nice flat walkway you spent all that time creating, will now be uneven and more difficult to walk on.
What does a good base involve? Once you have laid out the route and size of your path, perhaps with a garden hose or rope laid on the ground showing the outline, do the following:
- dig out the area of the path about 5" deep*. (NOTE: the actual depth will vary based on the thickness of the flagstone you choose to use for your path. You'll need 4" of base material compacted down to about 2" thick, a thin layer of mortar or leveling material then your flagstone.)
- add about 4" of a compactable base material like ABC (also known as crush'n run)
- tamp the base in using a hand or plate tamper.
Tamp your base material with a vibrating plate tamper.
You now have a solid, level foundation to construct your pathway on!
Because each piece of flagstone has irregularities in its surface and thickness, a "leveling bed" is needed; this can be made of sand or screenings (very fine rock dust) if you're doing a dry-laid walkway or a thin layer of mortar if you're doing a mortared walkway.
The Jigsaw Puzzle
Now, you can lay out your flagstone pieces! This is very much like putting together a jigsaw puzzle; obviously, the pieces won't fit together perfectly, but you can play with them so they come together in a pleasing pattern. If need be, some pieces can be sawn or chiseled to remove corners or edges that don't fit in the way they need to. Lay the pieces in the bedding sand/screenings or in the mortar and wiggle them slightly so they are level and firmly embedded in the base material. With a dry laid path, you can leave wider joints between pieces however, with a mortared path, you'll want to keep your pieces no more than 3"-4" apart.
Mortared Flagstone Path
Put stone in place.
Tap stone to make sure it's in place and level. Allow mortar to dry.
Once the flagstone pieces are set in place, mortar can be added between the joints. Colored mortars are available in everything from a light tan to black, so you can experiment with the look you want to achieve.
Dry laid flagstone path
Flagstone stepping stone path.
Finished walkways include a combination of mortared flagstone paths, flagstone with decorative gravel filler and decorative gravel paths.