Coping Stone

A coping stone usually overhangs the wall face slightly with a drip edge cut or ground into its underside, so water sheds outward instead of running straight down the face and into the joints below. It shows up on top of retaining walls, garden walls, columns, and chimneys, anywhere a flat horizontal surface would otherwise sit exposed to the weather, and it's typically set in a wider mortar joint to allow for a bit of seasonal movement without cracking loose. Coping can be cut natural stone, precast concrete, or manufactured units, but the job it does stays the same regardless of the material, and matching its width and profile to the wall below it is part of getting the detail right.

This is one of the more important pieces on any wall in this climate. The top of a wall is the most exposed surface there is, and without coping (or a crown, on a chimney) shedding water off, that top course soaks all winter long and freeze-thaw cycling cracks it apart from the inside, working down into the wall below it. Catching and resetting coping that's cracked or come loose early is a far smaller fix than repairing the wall damage that follows once water's been getting in unchecked for a season or two, which is why it's worth a look during any routine walk around the property.