Two radical timber buildings at the National Arboretum in Gloucestershire demonstrate how timber from trees felled in the routine maintenance of the estate were processed on site into structure and cladding, and constructed by volunteers and trainee carpenters.

Westonbirt Arboretum is an estate established in Victorian times by Robert Holford and now owned by the Forestry Commission. The Grade I-listed landscape has an internationally recognised collection of over 15,000 trees originating from China, North America, Chile and Britain. In the last few years the estate has benefitted from a £4.3 million regeneration programme, the first phase of which included the Visitor Centre by Glenn Howells Architects (subject of a previous TRADA case study).

The two new buildings, designed by Piers Taylor of Invisible Studio, are focused on the requirements of staff at the arboretum, whose management and care of the tree collection are critical to its sustainable existence. The brief developed into two buildings: the Machine Shed, where tractors and agricultural equipment used by the staff are housed and maintained, and the Mess Room, which provides communal staff facilities. Both buildings sit close to each other at the far end of the estate.

The Mess Room, 14.8 x 6.7 metres in size, has a simple cabin-like form and is carefully positioned to slot in among the large trees close by. The shape of its roof, two shallow inverted pitches, was determined by the angles of sun in winter, so that in winter months the adjacent yard would not be in shadow. The roof divides the building into two parts: a ‘messy’ area at one end containing kitchen, WC and drying room, and at the other end a large and lofty room where staff and volunteers can eat and take time out – its gable wall is lined with polycarbonate panels, filling the room with natural light. The drying room has a small loft above it for storage.

The Machine Shed is a 35 x 20 metre timber-framed building, large enough to house bulky agricultural machinery and fitted with overhead doors along both sides to give easy access. Timber was the obvious choice of material, and as the architect Piers Taylor explains:

“We particularly wanted to use the timber from the arboretum – as the client had an extraordinary resource which they hadn’t exploited previously for building. As a result, all the timber for these two buildings was grown and milled on site and used untreated for the construction with no further processing.”