No stone unturned

Arlington Row, Bibury

Arlington Row, Bibury, Gloucestershire

24 August 2012 by Alison Henry and Graham Lott

Local geology gives historic towns and buildings their unique character, but just as buildings fall into disrepair many local quarries have been lost too. English Heritage and the British Geological Survey teamed up to help protect this overlooked resource.

Alison Henry is an architectural conservator for English Heritage (EH). Her job is to make sure our historic buildings, grand and humble, survive the test of time. But finding the right stone to patch them up can be a challenge.

It's not just about matching the colour and texture. Stone ages and weathers depending on its mineral make-up and porosity; repair a building with something that's too hard and you'll hasten the decay of the surrounding structure.

But even when you can identify the original building stone, there's no guarantee the quarry it came from hasn't been filled in or built over.

"The sources of many of our common building stones are well-known," explains Henry, "But no one had systematically identified local building stones so sometimes there was no way of knowing if a local source was still available."

"Some of the information we had to work with was even misleading; the early listed building descriptions for south Somerset record almost all orangey-brown coloured buildings as being made of Ham Hill Stone, but many of them were built of less well-known building stones that were only used in a limited area."

And while a historic building is hard to miss, many small quarries have simply been lost in the mists of time. Local authorities are charged with protecting mineral resources, including building stones, and have to flag potentially important sites when considering development applications, but they can't protect resources they don't know about.

Shropshire in particular was a real eye-opener... some [quarries] were used for just one or two farms.

So EH commissioned the British Geological Survey (BGS) to help identify and record, county by county, the sources of all the building stones used in England. The Strategic Stone Survey would provide planning authorities with the information they need to find and protect important quarries - thereby ensuring historic buildings could be looked after too.

BGS was the obvious partner. The organisation already had a database of active mines and quarries plus an archive of building stones and their sources going back to 1835.

It turns out that Henry de la Beche, the first director of what was then the Ordnance Geological Survey, had a particular interest in building stones and always included them in his observations - laying the foundations for future recording practice as well as the 3500-sample collection of stones that BGS now looks after.

It was a huge task which demanded a thorough and systematic approach and the help of many local experts. BGS first trawled its own records and maps to produce a list of building stones for each county, used in everything from cathedrals to cottages, industrial buildings and even kerbs and paving.

Local geologists and building historians then set to work to identify villages and structures that represented standing examples of all the stones used. BGS then mapped and recorded the sources of every stone, using historic Ordnance Survey maps and other archives.

The information is all available on BGS's English Building Stone Pits (EBSPits) website, together with details of the scarcity of each stone, the extent of unworked sources and details of potential substitutes.

Graham Lott is the latest in a long line of BGS building stone enthusiasts. He welcomed the project as an opportunity for BGS to make the most of its existing records and knew that the final product would be crucial for meeting the growing demand for help with historic building repairs. In fact it turned out to be an even richer resource than he had expected.

Church Farm, Kenley, Shropshire

Church Farm, Kenley, Shropshire

"So many more stone types had been used than people realised," says Lott. "Shropshire in particular was a real eye-opener; the project turned up loads of small quarries that had served really small areas - some were used for just one or two farms. The geology there is very complicated and lots of stone types outcrop at or near the surface."

There is still work to do, but for the 34 counties covered so far Lott and Henry are confident they have identified most of the sites that operated as a building stone quarry.

Hits on EBSPits are increasing, as are requests for help identifying stones for historic building repair, on every scale from the redevelopment of St Pancras to local churches.

Local authorities have the evidence they need to protect historic quarry sites, and architects and conservators can identify likely sources of the stone they need - and not just for repairs.

"This work is really important for new build too," says Henry. "Finding the right match is crucial for the extension of historic buildings and for new buildings in architecturally sensitive areas."

So far the survey won't tell home-owners what their house is made of, but the painstaking work means England's historic towns and landscapes have a much better chance of being sensitively developed and enjoyed without losing their local colour.