In 1980 Brian Marson, chairman of the group, combed the countryside around Bath in search of a workable stone mine. Marson had worked with the Bath and Portland Stone company and knew the territory well. It did not take him long to discover Stoke Hill Mine, which had been used as an arsenal during the Second World War and had since lain dormant. Within four years the Bath Stone Company (it became the Bath Stone Group in 1996) had captured 80 per cent of the market in Bath stone.
The rich oolitic limestone bed lies 30m underground and extends over 40ha. The first saws used by bsg were based on a French model but proved unsatisfactory. Over the years the company's in-house engineers have evolved a bespoke machine which manoeuvres like a tractor and has a 1.2m tungsten- tipped blade which can be raised and lowered, and rotates through 90degrees to cut vertically or horizontally.
The working face of the mine comprises a base bed and a top bed. Normal extracting procedure is to cut the top bed into three blocks, by first removing the smallest, slightly wedge-shaped central 'wrist' block. Once the 'wrist' has been removed, the mason can snap off the remaining blocks. As blocks are cut, the exposed ceiling is secured by drilling holes and plugging them with epoxy resin; a series of metal plates is then bolted into place. Cut blocks are evened off in the mine and the dust residue saved for mortar mixes.
bsg has the capacity to produce up to 18,000 tonnes of stone annually. Half is sold for new-build projects, half for restoration work. The group claims that the high quality of the Stoke Hill bed enables it to mine larger, more uniform and more colour-consistent blocks than its rivals. Blocks are cut to architects' or contractors' specifications at bsg's manufacturing plant, Bath Stone Products in Yeovil, which opened 18 months ago and uses state-of-the-art diamond-wire profiling technology. About 40 percent of all stone ordered is cut and finished by bsp.
Managing director Nicholas Horton heads the group's technical services. He believes there is 'a huge ignorance about natural stone among architects' and that their training concentrates on steel and glass, at the expense of natural materials. His team offers advice at every stage of a project, from engineering consultations to providing schematic drawings detailing load-bearing fixing methods which ensure that orders are executed with maximum efficiency. On a recent scheme in Dallas, bsg staff flew to the us to oversee delivery of the stone and to advise the local architect on traditional fixing methods. bsg's exports to the us were valued at half a million dollars in 1997 and the market is expanding.
Stoke Hill was the only Bath mine able to produce blocks of sufficiently large diameter to reproduce the classical columns surrounding the Temple of Concorde at Stowe School, refurbished by Inskip and Jenkins. It was also able to supply exceptionally wide lintels for a student residence at Pembroke College, Oxford, designed by Eric Parry, and it supplied stone for the rebuilding of St George's Great Hall at Windsor Castle.
Horton and marketing director Elaine Dickerson are founder members of the stone association British Stone, officially opened in April 1997 and based at the Building Centre in Store Street, London. British Stone is committed to advocating the use of native stone in the uk and would like to see Bath stone outselling the currently fashionable French limestone.
The incorporation of Morhead Masonry, an installation team with 16 years' experience, into bsg last year, brought staff numbers to 60 and enabled the group to offer a 'one-stop-shop' package that should prove highly attractive to architects: a classic material, technical back-up and skilled craftsmanship. Since it opened in the 1980s, the group has maintained its major share of the market in Bath stone. Reserves are assured until 2040. 'It will see us out,' says Marson.