Barry Hunt, the author of this magazine’s ‘Ask the Expert’ and ‘Time of Tests’ columns, is a geologist and independent stone consultant trading as IBIS Ltd. When he is working he likes to get his hands dirty, so he can see for himself what has happened. He learnt the techniques of rope access so he could get up close to façades quickly and easily to see first hand any problems. He talks here about his work.

Underground, in the conditions of heat and pressure that created it, stone survives perfectly well for millions of years. Bring it to the surface and it immediately comes under attack. Its biggest enemy is water, but it also has to face an assault from wind, freezing temperatures, pollution and abuse by man. But the changes brought about by those attacks usually happen slowly (compared with the lifespan of people, anyway) so they tend to be ignored.

Barry Hunt calls it the Rock of Ages Syndrome. People think of stone as being almost timeless, so when it is used for building it gets neglected in anticipation of it lasting practically for ever.

“Restoration of stone should never be necessary,” says Barry. “If restoration becomes necessary it means the stone has been neglected – it has reached the point where it has completely broken down and needs replacing. If buildings were properly designed so water was thrown off them… if they were cleaned so all the lichen and plants growing on them were removed… water wouldn’t be retained on the surface and you wouldn’t get to the point where great big chunks of stone need replacing.

“I would like to change the attitude of people who own and run historic buildings. They say they haven’t got the budget to maintain buildings, but they often find the much larger budget they need to repair them when they have gone rotten.”

One way they discover they have problems is that lumps of stone fall off – although that happens surprisingly often and the owners frequently do not even realise it unless someone gets hit. “Bits of stone are falling off buildings all the time,” says Barry. “They are usually rotten so they break up when they hit the ground. They get swept up by street cleaning machines and kicked around by passers by. All trace is gone within a couple of hours.”

It is not only historic buildings that fail. Modern uses of stone have also proved inappropriate, especially when architects want the facade to be as flat as possible so there is nothing to throw off rain flowing down them.

When failures do occur it tends to be the stone that is blamed but, says Barry, stone is inanimate and performs in a predictable way that relates to its properties. If it fails it is because the way it has been used has not taken account of its properties.

He does not believe the introduction of the Construction Products Directive as a regulation in 2013 is going to change that, either.

Stone, like all building products, will have to carry a CE mark, which means it will have to be tested, but the tests themselves mean very little if specifiers do not understand the results. It is why Barry is currently reviewing the tests for stone in the ‘The Time of Tests’ column in this magazine – you can read the latest on

page 6 of this issue.

Do we need all those tests? Barry believes they can be helpful but a lot of the preliminary work is just about knowledge. Many stones can be summarily ruled out of any particular project without any testing because experience tells you they would be inappropriate.

A lot can be determined about those still in the running through petrography – looking at them down a microscope. “In the first year after I set up on my own I hired microscopes but then I bought my own – £50,000, but they have paid for themselves many times over. They are vital.”

Only with the preliminary rejection of clearly inappropriate stones is it necessary to start thinking about testing.

CE marking will mean that suppliers will have to present test results in order to be able to tick all the boxes, but they are likely then to say: there’s the information, you do with it what you want.

Barry: “We have a test result saying one stone is stronger than another. But that doesn’t mean much. It doesn’t say how well each stone will perform in use. All tests can do is give us a starting point. They don’t give us an end point. There are stones that can be difficult to use but if you understand the stone you can use them – although the cost might be so great you would decide not to.”

And there is always a capital cost compromise. Barry firmly believes that with the right advice the future problems that designers and developers build into their projects could be eliminated. But there is a current price associated with eliminating future problems and people generally don’t want to pay it because they discount the future.

Take a project where Barry is currently the stone consultant. It is a road in London. Perfectly good Chinese black gabbro and pink granite are being used. Barry detailed the stone element of the road. “I designed it to last 1,000 years. It would probably have lasted 2,000. But the funding wasn’t available to build it that way.”

The big problem was the spaghetti-like tangle of services under the road – something like 1,000 individual cables, water pipes, gas pipes, sewers and access tunnels.

In keeping with current practice, the road is going to be built over those services, which will mean it is dug up from time to time to repair them. The once-and-for-all solution would have been to move the services and provide easy access to them for maintenance. That would have been time consuming and costly now, even though it would save money in the future. So there is a compromise. Barry: “We have set very high standards but not as high as they could be. Will our descendants understand our decision?”

A fair proportion of Barry’s work is about finding out what has gone wrong, which troubles him. The reason consultancy advice is not sought at the start of a project is usually an attempt to save money or because those involved do not understand they need it.

Barry is a registered expert witness and does appear in court cases, but he tries to keep away from courts if possible because that is when problems become really expensive.

He has known people spend tens of thousands of pounds on court cases about problems that would have cost a couple of thousand to put right. Once the bills start mounting up, the parties involved have to continue in the hope of being awarded costs when the case is finally resolved.

The courses Barry has attended to become an expert witness have confirmed what he had already worked out for himself: he is not working for the person paying him, he is working for the stone, or the project in which it was used, because it doesn’t have a voice. Courts don’t want to know about the client, they want to know about the project.

His priority when he is called in after a problem has arisen is to find a solution – if possible without going legal, although he often is not consulted until it already has gone legal.

Such cases are often a source of future business for him because once a client has been through the dispute process they are more willing to seek advice at the preliminary stages of future projects.

To resolve disputes he has to be a detective and get to the truth about what has happened but, he says: “It’s always about the patently obvious. It’s looking for the simple facts; getting the story together.”

To do that he likes to get his hands dirty. He doesn’t ask other people to remove stones or dig up screeds, he does it himself. Feeling what is happening and how the structures are responding tells him a lot about how the work has been carried out.

It was why he learnt roped access (he says it is not abseiling because he goes back up, as well as dropping down). He wanted to see the facades for himself, not rely on the reports of others.

He decided he had to learn when he was surveying the buildings of Broadgate in London after the IRA bomb explosions of 1992 and ’93. He was working there just before he left consultants Sandbergs in 1994 to go to another consulting firm, STATS, which he left in 2002 to branch out on his own. He likes the Broadgate buildings because they use traditional detailing themes to shed water.

He was using window cleaning cradles and was being helped by people on ropes, who reported to him so he could interpret their information. He thought how much easier it would be if he could move rapidly over the face of the building on a rope himself.

At Broadgate, questions were asked about what was bomb damage and what was thermal shock damage from the flame texturing that had been applied to the cladding before it was installed. “In those days we didn’t know about the cracking associated with flame texturing and the question was: if the blast hadn’t happened would the stone have performed? And yes, it would have.”

The tools of Barry Hunt's trade are microscopes and computers. But when he is surveying buildings he likes to be hands-on, even when that means hanging from a rope 100m or even 200m in the air.

“I have just been quoting for a big building in London and I have been trying to convince them that you can use power tools from a rope. People say what if I accidentally cut the rope. Well, what if I accidentally cut my throat? I regularly have to take coring drills on a rope with me to take samples. It’s quite a simple thing to do.

“In one job in the City of London I had to pin back huge concrete cladding panels. If they had fallen they would have crashed through the floor and into the underground station below. We did it at night – there was no big kerfuffle. No-one even noticed. We drilled through at the joint locations and restrained the panels. Peter Harrison from consultants Harrison Goldman had done all the calculations and determined the fixings then came to me because he knew I could do the work.

“In Birmingham we completely netted a

12-storey marble-clad building using rope access without anyone even noticing. The Carrara marble cladding had started bending – it is a familiar problem. We drilled through the marble to the supporting structure and resined in anchors to fix the netting up so it is completely independent of the cladding.

“There are wires at each floor level so if a stone does fall it will only fall as far as the next floor plate. We spent four weeks installing the net. You can only just see it – it makes the marble look like tiles. It was supposed to be up for a year until they could replace the cladding but nine years later it is still there, although none of the cladding has fallen off.”

Barry does not turn up on-site in a suit and tie. He likes to be able to get in among the masons and see what they are doing and, if he needs to, to get his hands on the stone and materials being used. It gives him a better idea of what is happening.

For the past year he has also been attending an adult education centre in Gants Hill, near his home in East London, where he has been learning to carve stone under the tuition of Paula Haughney.

He says: “It’s something I have always wanted to have a go at and I have learnt so much about stone from it – and I have a hell of a lot more respect for masons and artists now.”

He started off carving soft soapstones and alabaster but moved on to Bath stone, hard Portuguese limestone and even granite. He is currently working on a bas relief of the first of the labours of Hercules in slate. He says he would love to produce all 12.

He says the work has given him a completely new understanding of stone. For example, he now realises you don’t chisel granite, “you slowly pulverise it”. He is learning how to hold chisels without ending up with aching fingers.

“When I look at carved stone now – not necessarily sculptures but even mouldings such as egg & dart – I have a better understanding of the work that has gone into it. It has helped me to understand how unreasonable people are being when they expect stone to be perfect.

“Some people get focussed on very minor imperfections but if you have just cut 2m of egg & dart and you make a small mistake it is unreasonable to expect that work to be thrown away and started again. Or, if you do expect it, you should expect to pay a very high price for it.”