Rock is a great material to work with. It’s cheap – especially when you live rurally where you can pick it off the ground – and easy to use. It’s also strong and natural, the earth’s building blocks. The downside is that it’s fairly labor intensive and slow, compared to other building methods.

The principle of rockwork is simple. It’s exactly like laying bricks, other than your bricks are not uniform in size and shape. Basically, each level overlaps the one below it. The join between two rocks is a weak spot. You counter this by placing a rock on top of that join to bridge it.

Any wall should not lean, unless that wall is part of an arch or dome. If a wall that is supposed to be straight leans, the weight will be shifted away from the center of the wall, and will eventually crack and fall down. So make sure each level of rocks is plum and level with the one below it.

Beyond that, you pick your style of rockwork. Some people like straight, uniform faces; others prefer a more rounded, less perfect effect.

Mortar
You can dry-stack rocks (using no mortar), but in order for them to be truly stable and durable, you should use rocks that fit very well together.

Mortar makes the jigsaw aspect of rockwork a little easier. Rocks still need to fit pretty well together, but the mortar will absorb small imbalances. Many people use concrete as mortar, adobe works too.

The idea of mortar is not to let rock touch rock. You put your mortar on any exposed rock, excluding the “faces” of the rocks, and stack a rock on that mortar, much like brick laying.