Westonbirt Arboretum, Gloucestershire

Fresh Sawn Western Red Cedar Bias Cut Shingles & Air Dried Western Red Cedar Profiled Strip Cladding

This project at Forestry England’s Westonbirt Arboretum uses homegrown certified air dried Western Red Cedar profiled into horizontal strip rainscreen for internal and external cladding and PEFC Boas Cut Shingles sourced in Normandy, France for the roofing.

The Westonbirt Arboretum video gives an insight into this Green Apple award winning project.  The National Arboretum is one of the most spectacular collections of trees in the world so it was only fitting that timber should play a key role in the design of the Visitor Centre.

In 2010 the Forestry Commission, who own and manage the Arboretum, commissioned Glenn Howells Architects to develop a masterplan which, over the course of several phases, would improve the experience of visitors to the site. Improvement was needed; parking was haphazard; a single ticket hut caused long queues; toilets and café were scattered around the site and there was nowhere to provide information.

The new building is the start of every visitor’s journey to the Arboretum. Discreetly set in a natural landscape hollow, it is deliberately modest in scale to minimise its impact on the historic landscape and to maintain the main focus on the collection of trees. Materials have been carefully considered; in response to its sylvan location, the building has been designed as an exemplar of the use of UK sourced timber and to demonstrate the aesthetics and capability of green materials in construction.

A key aspect of the design was the need to achieve a smooth external curved appearance to the building; the choice of timber for the external cladding and its detailing was critical. Green UK-sourced western red cedar strip profiles were chosen and proved an excellent material to create the curve; laid horizontally, they have sufficient elasticity to curve smoothly but are robust enough, untreated, to deal with the relatively exposed location. The cladding battens were deliberately fixed with deep shadow gaps between to allow them to move slightly while the appearance of the curve of the building remains consistent. The roof is clad with untreated western red cedar bias cut shingles; the bias cut offered better durability and quality on a sawn shingle without the irregularity of hand riven shakes.

For the rainscreen cladding we used locally sourced logs, cutting a allowing the blanks to dry slightly to enable profiling here in the workshop.

The roof shingles are also WRC but they’re sourced from Normandy, France where the bias cutting of timber is common practice in the production of barrel staves. We don’t know of any bias cutting service in the UK, but we can’t emphasize enough the benefit of having the full intact grain, especially for this roofing application.

We were proud to work in association with TRADA on the production of this video to support the use of local timber. It givesan insight into this Green Apple award winning project.  The National Arboretum is one of the most spectacular collections of trees in the world so it was only fitting that timber should play a key role in the design of the Visitor Centre.