Stone once raised twelve-storey homes, and builders are teaching it new tricks
In the 1690s people lived in stone apartment blocks twelve storeys high. Today stone mostly hangs as a thin decorative skin on concrete frames, even though many kinds outperform concrete in compression and cost far less energy to produce. A small group of engineers and architects wants to put it back to structural work.
Working stone is among the oldest trades humans practise, and it splits into distinct jobs. A quarryman frees blocks from the rock face. A sawyer mason turns those big blocks into dimension stone with diamond-tipped saws, and a piece cut to order on every face is called sawn six sides. The banker mason then works in a shop from templates, shaping anything from a plain chamfer to window tracery, taking care that each stone sits in the wall the same way up as it lay in the ground. On site, a fixer mason lifts and sets the finished pieces with lime mortar, dowels and cramps, while memorial masons cut gravestones and carver masons produce figures, animals and foliage.
Classical methods vary widely. Ashlar uses dressed, squared blocks; rubble is its rough opposite. Laying a beam across posts, the trabeated system, is older than Stonehenge and was refined by Egyptians, Persians, Greeks and Romans. Dry stone walls hold together through friction, weight and the shapes of the stones alone, and cyclopean work stacks huge boulders, sometimes cut into polygons so they lock together.
Stone spanned 50-metre bridges in Roman times and reached roughly 65 metres in medieval cathedrals. Brick and steel-reinforced concrete pushed it aside anyway. Veneer used as cladding now tends to be about an inch thick and must stay under 15 pounds per square foot, so the wall behind it needs no extra support.
Newer techniques aim to make stone carry loads again. After the Second World War Fernand Pouillon worked with Paul Marcerou, an engineer at a quarry in Fontvieille, to borrow precision saws from the timber trade, letting machine-cut blocks go up quickly as load-bearing walls. Designers now compute complex vaults with CAD, thread tendons through drilled stone to post-tension it, and cut quarry stone to brick size; such stone bricks cost about the same as clay ones, emit far less carbon and need no expansion joints. In London, 15 Clerkenwell Close uses a precut post-and-lintel stone exoskeleton.
Source: Stonemasonry
