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With St Chad, St Michael and St Aidan watching every move, Mark Whyte carefully takes a sample of grout from the beautiful 120-year-old stone reredos near the altar of Taranaki Cathedral Church of St Mary.

Whether the saints approve, it’s hard to tell – the stern look on St Chad’s face suggests otherwise – but the work has their best interests at heart. 

Stone sculptor Mark, and business partner stone mason Robin Ayers, from Christchurch company Goldfield Stone Ltd, are in New Plymouth to investigate how best to remove and restore the striking ornamental stone and mosaic panels, and the small onyx and marble columns that complete the reredos, before work on earthquake-strengthening the Cathedral begins.

As The Cathedral Project remediation and design manager Jenny Goddard explains, keeping the reredos out of harm’s way while work is done is only part of the project team’s concern.

“While the strengthening work is some time off, we are considering moving the reredos now because it is being damaged by damp coming through the wall – the longer it is left, the worse it will get,” she says.

The dampness is causing the stone, believed to be sedimentary limestone from France, to weaken and crumble. A cream coloured dust gathers at the foot of the left-hand panel and is regularly vacuumed away.

There are also concerns for St Chad and his saintly companions, who were added some time after the reredos was installed at the suggestion the stone panels needed brightening. Some of the individual mosaic tiles have popped off because of the dampness and have been lost.

“This isn’t a new problem – it has been visible for more than 15 years – but no-one has known how to tackle the problem,” Jenny says of the dampness issues.

“The strengthening work will give us the opportunity to fix a long-term problem with the gutter above this wall. A bonus is that the grout infills that will be used to strengthen the walls will also assist in preventing moisture movement through the stone to the interior, so the reredos will be in a much safer place when it returns.”

For Mark and Robin, the Taranaki Cathedral work is an area of expertise. They have many years’ experience, and post the 2011 Christchurch earthquakes have undertaken a large amount of stone and brick restoration work for some of the city’s most important heritage buildings, including St Michael’s and All Angels Anglican Church, the Bridge of Remembrance and Triumphal Arch, Christ College Chapel and St Barnabas Church.

From their on-site investigations at Taranaki Cathedral, they will write a detailed report on how they plan to complete the removal and restoration of the reredos. This will be assessed by a conservation architect, who will make his comments before the plan and process can be approved. The proposed work will also be discussed with Heritage New Zealand.

Goldfield Stone expects the reredos to weigh about 3.5 tonnes, and its removal will be a delicate operation.

It is likely it will first be separated into smaller, manageable pieces. This will be achieved by cutting through joints grouted during the original installation, cutting the horizontal joints between stones, known as bedding joints, and disconnecting the reredos from the church stone walls. 

Then the pieces will be placed on hydraulic tables on wheels and put in made-to-suit protective boxes before being stored in a temperature controlled environment, keeping the stone safe and allowing it to dry out before restoration.

“We have to be very careful and not rush it,” Mark says. “In total the work will take at least a couple of weeks for two to three people. If a small piece, such as a chip, comes off during the removal, it’s important we pick it up, put it in a bag and keep it for its conservation value.”

Every part of the work will be photographed and documented so that the removal process can be perfectly reversed once the cathedral strengthening has been completed and the reredos has been restored.

Restoration of the reredos will involve cutting away some parts of stone that are irreparable, sourcing the same stone, and sculpting a new piece to fit seamlessly. It is likely the reredos will also be carefully cleaned, using no solvents, before being reinstalled.

Missing pieces of mosaic will be matched and replaced, returning St Chad and his friends to their saintly glory, and perhaps putting a smile on his face.

The reredos at the back of the altar at Taranaki Cathedral of St Mary.

Stone sculptor Mark Whyte, of Christchurch company Goldfield Stone Ltd, examines the stone and mosaic reredos at Taranaki Cathedral Church of St Mary.