Introduction
roundpole design & build
15 Mar 2005
We designed & built this structure at Westonbirt Arboretum in 1993-4. It uses timber from site, with a turf roof, and provides covered work space for green wood demonstrations, and school groups.
The design for this shelter, which measures approx. 9m x 10m in plan, was inspired by its position in a piece of ancient woodland, of oak standards and hazel coppice, known to have been managed in this way for 1000 years. The sprouting pole columns echo the form of coppiced or pollarded trees.
European larch poles were being extracted from the site, in a project using dray horses. We were able to utilise these forest thinnings, that are taken out to allow the remaining trees to mature to timber size with enough space.
The poles are jointed using a system designed by ADAS (Agricultural Development Advisory Service) in the 1980's. This was designed to turn almost worthless young green timber into valuable building components, with the aim that farmers could potentially build agricultural buildings in this way.
The joint uses a steel flitch plate inserted into the pole ends, which is then fixed through with steel tubes containing galvanised fencing wired strands which are wrapped around the pole, tensioned and twisted to tie in place. This counteracts the splits that open up as the pole dries.
Oak planks form the roof deck under the waterproof membrane and turf. These also came from on site timber.
None of the timber is treated with chemical treatment. Instead, traditional detailing keeping the timber dry and well-ventilated, and choice of durable species ensure longevity.