The poet Robert Frost described his own formula for mending tumbled-down stone walls: "And some are loaves and some so nearly balls/ We have to use a spell to make them balance..." A stone mason might just call it heavy lifting. There are a few ways to build a stone wall, including the old stacked stone method that Frost used. Stones can be natural and dug up from the land, or quarried, shaped, steel-reinforced and cemented in place.
Stacked Stone Walls
The oldest and simplest stone walls are hand-stacked stone without any mortar, frames or structure, except their own weight and the shapes of the stones chosen by the waller. The stones are selected for flat sides that will stack securely. Stone masons break off small pieces to make a larger stone fit a space. The smaller stones are tucked into chinks in the wall to stabilise it and fill it in. This is the greenest form of stone wall—when the stones come from the area or even the ground the wall is built on. The artist Andy Goldsworthy in 1997 brought traditional wallers from England and Scotland to split and stack stones from the property at the Storm King Art Center in New York State. His 2,278-foot winding wall is a permanent art installation that harks back to a long-disappeared wall said to have once existed on the site.
Traditional Mortared Walls
Mortared walls are newcomers in the history of wall building. Cement wasn’t invented until the mid-1800s, but once it became available, stone masons started to use it in place of the small stones, to fill in spaces between larger stones in their walls. Using mortar means that a stacked stone wall can be a vertical wall rather than slant inward towards the top to keep the stones from tumbling out. The mortar allows the wall to rise higher because it “glues” the stones together so there is less chance they will shift. But this method still calls for skill and talent in designing and constructing the wall. The only "modern" addition to the ancient method of stacking stones is the cement.
Slipform and Veneer Stone Walls
Slipform stone walls are built by creating a form of 2-foot high, or taller, sides. Stones are lined up along the inside of the form with their best-looking surfaces facing out. The hollow inside is filled with a mix of rebar—stabilising rods—and concrete. When the cement dries, the forms are removed and the freestanding wall is stone on the outside, reinforced concrete in the middle. Veneer stone walls are breeze block or concrete walls with stone veneer cemented to the surface after the inner, concrete wall is built. Both slipform and veneer walls are strong and can be built tall because they include steel bars inside the cement construction.