Minster cracks up

HIGH up in the scaffolding that cloaks York Minster's East Front, the wind whips around the corner of the building. Up here, suspended dizzyingly more than 100 feet above the ground, it is easy to see how the great stone buttresses that support the magnificent cathedral have been eroded by time.

Stonemason's foreman Simon Trotter lays his hand on a rough, weathered cornerstone. Deep grooves and channels have been worn into the 600-year-old stone down the centuries.

"It's wind and water," he explains. "It's like a river. Over time, as the wind drives the rain it forms a channel in the stone that the water flows along. After hundreds of years, the channel gets wider."

These channels, scored everywhere across the Minster's East Front by centuries of driving wind and rain, aren't the only signs of damage. The delicate tracery of stonework that supports the priceless stained glass in the East Window is also scoured and worn away by wind and time. And the great statue of St Peter that sits at atop the window is almost faceless thanks to erosion.

It is not only wind and rain that has caused the damage. Pollution has played its part too. In some places the stone is pocked and scarred by the corrosive effects of black sulphates. Run your hand across the stone, and the sooty black substance crumbles off.

More worrying than all this cosmetic damage, however, are the structural problems. Everywhere, cracks and fissures run through the ancient stone. Some have been caused by water getting into natural cracks in the stone, then freezing to form ice.

"When it freezes, it expands," says Simon, "and it is just like driving a wedge into it." He indicates the corner of one stone that is in the process of cracking, and will eventually shear off if the stone isn't replaced.

Other damage has been caused by earlier, bodged attempts to repair the Minster.

Stephen Mills, the Minster's superintendent of works, gestures at a crack through the middle of one of the great load-bearing buttresses. It runs up way above our heads, disappearing behind the next level of scaffolding. Attempts to repair it with cement and iron holding pins in the past have only made it worse.

"This is a good example of what we're worried about," says Stephen. "The iron rusts and expands and cracks everything around it. The crack runs all the way through here now."

The damage to one of the two great pinnacles that top the East Front is so bad that if you stand in the spiral stairway inside, you can see daylight through joints between the stones. "It is in a terrible state," Stephen says. For safety's sake, several of the smaller stone pinnacles that surround the base of the largest pinnacle have already been taken down.

There is no immediate danger of falling masonry from the East Front, Stephen insists - especially now the scaffolding is in place. But the time has come for a major restoration job.

Repairs were carried out to the East Front at the beginning of the last century, and again in the 1930s and 1970s. But the last major restoration work was about 180 years ago, by the then master mason William Shout. Much of the stonework supporting glass in the lower part of the great East Window was replaced then.

Shout's restoration of the East Front came after he had finished restoring the West Front. Almost 200 years on, the cycle has been repeated - restoration of the Minster's West Front was completed only in 2000. It gives a good idea, Stephen Mills says, of the cycle of major work needed to keep the Minster in good shape. "A period of about 200 years," he says. "It's an ongoing project. Cathedrals never get finished!"

Although it had been known for some time that the East Front was in need of restoration, it wasn't until the scaffolding went up last autumn that surveyors were able to study the stone of the upper East Front close up. Then it became clear just how much work needed to be done.

"After looking at the buttresses we came down and it was quite depressing, really," says master mason John David. "There was far more to do than we thought originally."

Now, after painstakingly studying each stone in the Minster's East Face, often tapping stones with a metal chisel to listen for the tell-tale signs that distinguish a crack, the full extent of the problem has been revealed.

More than 60 per cent of the stonework - something like 10-12,000 stones - will need to be replaced, much of it in the upper half of the East Front: buttresses, pinnacles and the delicate tracery of stone that holds together the upper sections of the window.

Repairing the window stonework alone will mean taking all the glass out, bit by bit, while the crumbling stone is replaced, greatly adding to the difficulty of the project.

It is a mammoth task and one that Stephen Mills estimates is going to take anything from eight to ten years to complete. The cost will run into millions, and the Minster's East Front is going to be covered in scaffolding for a long time.

"That's a great shame," Stephen says. "But it is one of those things we just have to put up with if we want to keep the Minster intact."

Doing the job stone by stone

The process of replacing thousands of weathered, cracked and damaged stones in the Minster's East Front will be complex and painstaking.

Each stone has to be precisely measured, its size and shape and the details of its carving recreated exactly so the replacement stone will fit perfectly into the gap.

In many ways, says master mason John David, it is a far more difficult job than building from new. "It is much easier building new because you are not quite so constrained. When you are restoring areas, each new stone has to fit exactly."

Restoration isn't expected to begin until April, but John has already been working with surveyors for a couple of months, assessing exactly what needs to be done. At the end of this month, he will officially begin the process of "setting out".

That will involve climbing the scaffolding day after day with a notebook and drawing materials to take detailed measurements of every single stone to be replaced.

Then, down in John's workshop, these measurements will be turned into detailed, full-sized drawings. The drawings themselves will be used to produce the zinc templates from which workmen in the Minster stoneyard will work when they begin to carve the replacement stones.

Limestone from a quarry near Tadcaster - just a few miles from where the stone used to originally build the Minster was quarried hundreds of years ago - will be used for the restoration.

There will be no cement, no metalwork that could rust and corrode, and no Ketton stone. This type of stone was used for repairs at the beginning of the last century, but was discovered to react badly when it comes into contact with the original limestone.

Lessons have been learned, John David says - and as far as possible the techniques and materials used in the restoration will be as close to the original as they can be.

Work will begin on the damaged top pinnacle, which will have to be completely dismantled, and will proceed gradually, stone by stone, down the East Front.

The Minster has a skilled team of masons ready to begin. Men such as Martin Coward, who down in the stoneyard is putting the finishing touches to a carved gargoyle that will soon take its place on one of the Chapter House buttresses. This magnificent creature seems to be wrestling its way out of the stone in which it is imprisoned.

Martin shows me the groove that runs along its back and plunges through a hole in its mouth. This is where water will pour out of the creature's mouth once it is in place, he says proudly.

The loving care being lavished on this one piece gives an idea of the scale of the task ahead. The challenge is made all the more difficult because the East Front leans out, John David says - putting the great buttresses under greater strain and making it more difficult to remove and replace each stone. You can tell how bad the lean is by tapping the buttress stones, he says. The ringing note is higher than it should be: a sign of compression.

Also, the East Window itself is buckled - and the stones used to anchor steel cables installed in 1970 to hold the window back are all cracked. Each one of the anchor stones will have to be replaced, says Stephen Mills.

"To do this, the tension on the cables must be relieved and the cables disconnected." That part of the project, he jokes, will be carefully planned to coincide with his annual leave.

All in all, it is a daunting challenge, but an exciting one. "I'm looking forward to it," John David says, standing over the plans in his workshop.

Updated: 11:33 Thursday, January 13, 2005