Flagstone

Flagstone can be laid as irregular pieces fitted together edge to edge, sometimes called crazy paving, or cut into more regular rectangular shapes for a cleaner grid pattern with straighter joint lines. It's set two main ways: dry over a compacted gravel and sand base, or mortared over a solid concrete slab, and the right choice depends on the application, the traffic the surface needs to handle, and whether the patio is meant to flex slightly with the ground or stay perfectly rigid. Thickness varies by stone and application, and thicker stock generally handles more foot traffic and settling without cracking, which matters on steps and heavily used walkways especially.

In this climate, a dry-laid flagstone patio needs a properly compacted, well-drained base underneath it, because if water sits under the stone and freezes, individual pieces can heave unevenly over a winter. A mortared flagstone surface avoids that shifting but only if the slab and footing underneath it are stable, since the flagstone will crack right along with whatever's holding it up if that base moves. Either way, the base does more to determine how a flagstone patio ages than the stone selection does, which is why we spend more time on base prep than on picking out slabs, and it's the part of the job a homeowner never actually sees once the patio is finished.