Article from Riba journal of the 20/01/2022
Extract
We met Ateliers Romeo when making a helical all-stone staircase for a private house. The convention is to incorporate steel stringers and substructure, bolted to the walls and floor and dressed in stone, but I’d read that engineer Price & Myers had rediscovered how to make ‘part-cantilevered, part-reciprocal’ stone stairs – a method forgotten after the first world war. Each tread rests on another, but is keyed into the wall to stop it twisting; the smaller the overlap the more elegant the stair.
In France stonemasons are still trained in that technique, and the job went to Ateliers Romeo, a French company based in Italy’s stone industry region. While visiting them we saw raw master blocks coming into the yard which looked like they might make columns. They explained that in France and Italy, stone is still used for loadbearing structure, and is cheaper and quicker than using steel or concrete and stone cladding. It used to be called ‘austerity construction’; Fernand Pouillon’s post-war apartments on the Marseilles waterfront cost 10% of what Corb spent at the Unité d’Habitation. Our sustainability consultant later confirmed that a stone structure is also 92% lower in embodied carbon than a stone-clad steel frame.
It was there that we got the inspiration for a number of structural stone projects that have followed, including our office at 15 Clerkenwell Close with another French-trained mason, Pierre Bidaud of The Stonemasonry Company; a 10-storey block with an exoskeleton of lava stone on site in north London, with Ateliers Romeo; and series of private houses with loadbearing single-and double-skin walls of stone and pools using contemporary versions of medieval rib vaults.