Raising the roof at Henry VIII’s holiday home
More than 150,000 visitors to a Tudor mansion in Hampshire were able to see roof conservation works from atop a giant scaffold, as contractors below tackled wonky chimneys, rotten timbers and a colony of obstinate bats. Stephen Cousins reports.
It’s hard to know what Henry VIII would have made of the spectacle surrounding The Vyne, a sprawling red-bricked Tudor mansion near Basingstoke in Hampshire, which over the past 15 months has been the subject of a £5.4m reroofing project.
The fearsome monarch and his ill-fated wife Anne Boleyn once stayed at the property in 1535, but since February last year it has been encased in a giant weatherproof shell, comprising over 339 tonnes of scaffolding, designed to protect the mansion as specialist craftsmen carry out vital repairs.
Project The Vyne reroofing
Client National Trust
Main contractor Ken Biggs Contractors
Programme January 2017 to July 2018
The freestanding scaffold supports a raised walkway from which over 150,000 visitors watched work as it progressed on the pitches and valleys below.
It was one of several challenges faced by the construction team, led by Bristol-based Ken Biggs Contractors and client the National Trust. Around 71,000 roof tiles will be removed and replaced during the 18-month project, chimneys are being reconstructed and the whole programme has been dictated by the roosting and hibernation patterns of a bat colony.
The Vyne, at Sherborne St John, has a long and intriguing history. It began life as a cluster of medieval buildings, but was expanded to create a grand Tudor palace for William Sandys, who became Lord Chamberlain to Henry VIII in 1526. Ownership passed from the Sandys to the Chute family in the 17th century, before the Vyne was eventually bequeathed to the National Trust in 1956.
The mansion today is roughly a third of its original size. The 1,600 sq m roof has been extended and repaired over the centuries to become a higgledy patchwork of red tiling, off-kilter chimneys and roof pitches coming together at odd angles.
The National Trust had a maintenance programme in place, but the situation worsened in 2013 when severe storms over the Christmas period left the roof battered and leaking.
Andrew Harris, project manager at the National Trust, explains: “Our five-year inspections had flagged up the need to programme in more renewal work, but the bad storms caused lots of issues with water ingress in different parts of the mansion.
The Vyne’s north facing front (National Trust Images/Arnhel de Serra)
A particular concern was a chimney in the central valley that was leaning badly with a horizontal crack at the base – a support cage had to be installed around it as a temporary measure.
“Ad hoc repairs were not going to cut it any longer; we had to urgently intervene and bring forward a wholesale replacement project, originally planned for 10-15 years’ time.”
There was little documentation related to the roof structure and the alterations over time, so an extensive feasibility study was launched in 2015 to assess the repair work required.
“Although we had a basic under-standing of the structure and how it had evolved, it was only derived from what we could see from the inside. Removing areas of tiles and coverings enabled us to take a good look at everything,” says Harris.
Mortar samples were extracted and sent for analysis, which formed the basis of the specification for the lime mortar used to rebuild the chimneys and other brickwork. Fragments of the original Bath oolitic limestone that had fallen from the building were analysed to find a close geological match used to repair coping on castellated sections, including merlons and embrasures.
National Trust Images, Gary Marshall
Just 15-20% of the clay tiles across the entire roof were considered salvageable, and most of those were in such poor condition the decision was made during consultation to remove all the tiles and replace them with new ones.
Six types of tile from different manufacturers were shortlisted. The product specified is a traditional handmade clay tile, formed in a mould and bearing the handprint of the maker on the reverse.
The brick chimneys were leaning at such precarious angles they were considered structurally unsound. New straight chimneys were built using bricks handmade to the same dimensions by the only remaining manufacturer in the country that still uses a wood-fired kiln. “Wood firing creates various nuances and different colours depending on the location in the kiln and firing temperatures,” says Harris.
A project archaeologist had a watching brief to inspect and record all roof timbers and structures. It was considered remarkable that, given the deterioration of the tiling, the wood below was in such good condition with limited rot. The anticipated £200,000 of timber repairs was cut by over a half to around £90,000.
However, not knowing the extent of the rot in joists and rafters before the exterior tiles, felt and battens – and centuries of bat and bird droppings – had been removed added time constraints.
Ken Biggs contract manager Kevin Brooks says: “The oldest timbers could not be removed and had to be repaired in situ. It took time to assess the damage, develop the design for modification and structural repairs and then wait to get the engineer’s approval.”
Close-up of tiles being removed (National Trust Images/Karen Legg)
Chimneys being repaired (National Trust Images, Virginia Langer)
Dendrochronology (tree-ring dating) revealed that some timbers over the chapel roof were original and from trees felled in 1524. Others, over the oak gallery, at the western end of the mansion, were dated to 1526.
Chisel marks in some of the wood gave clues to the original method of construction. Carpenters had inscribed roman numerals when jointing the timbers at ground level so they could be lifted into position in the correct order.
Arguably the biggest obstacle to the work was nocturnal. The National Trust always presumes that its properties are frequented by bats, but surveys carried out during the feasibility stage revealed the creatures inhabited most of the mansion roof.
Bats go through a cycle of hibernation in the winter and nesting in the spring, so there were specific times when work had to be put on hold in certain areas. For example, the discovery of a maternity roost over the chapel forced trades to down tools until the young had left.
A member of the team inspects exposed lathes and beams (National Trust Images)
Bats can change their sleeping location, so the programme could be disrupted at any time, says Brooks: “As soon as we found any bats when stripping off the roof, we had to stop work and call the ecologist, who was not always available to immediately come to site.”
The new roof incorporates special features so the bats can continue to roost in the building, including bat tiles, bat access points, and bat ladders (small tunnels the creatures can crawl through to enter attic spaces).
Animals from the 16th century also made their mark on the project. Tiles removed from the roof had the footprints of dogs, cats and sheep on the reverse. It is thought the animals walked over them when they were newly made and laid out in the yard to dry in the sun.
The project is now nearing its July completion date. The National Trust faces the herculean task of unpacking The Vyne’s collection of over 3,000 historic objects, boxed up before contractors arrived on site, and returning them to the mansion.
National Trust Images/Karen Legg
A scaffold with a view
A public walkway gave visitors a closer look at the roof conservation work
A giant freestanding scaffold, with enough metal pipe to stretch 41 miles, shrouded The Vyne for the duration of the conservation project.
The structure provided access for contractors and materials and included an upper-level walkway with a separate lift from which visitors got a bird’s-eye view of roof conservation work (pictured above).
The National Trust receives no government funding, so this “conservation in action” feature was considered critical to help the building raise additional funds.
Andrew Harris, project manager at the National Trust, says: “A scaffolding designer was appointed to develop a design configured to provide the best views of conservation work. Tendering contractors could easily see what we were trying to achieve and price the work based on the same information.”
Over 100 volunteers were trained to operate the visitor lift, understand health and safety and evacuation procedures and explain the construction and roof to visitors.
The scaffolding shell took over five months to erect, starting in October 2016. The public walkway extends around the building perimeter on the north and parts of the east and west elevations. One section extends across the centre of the mansion roof in a single span.
“The structure spans between vertical scaffold towers at either end and required lots of RSJ beams and beefed up scaffolding to transfer loads down to ground level,” says Harris.
All the walkways were pre-assembled on the ground and lifted into position by tower crane in a single day, followed by the giant roof trusses the next day.
Construction materials and workers accessed the site via a second lower-level walkway via a loading bay in a separate contractors’ compound on the south side of the building.
Public access to the walkways ended in March. The scaffold itself will take several weeks to dismantle ahead of the project’s completion.