23 June 2017
Timber walkway with treetops view!
An eye-catching timber walkway that gives visitors an unprecedented view of the treetops at Westonbirt Arboretum is the subject of TRADA’s latest case study.
Stihl Treetop Walkway, the winner of the Commercial and Leisure category at the 2016 Wood Awards, was designed by Glenn Howells Architects and is the latest in a series of building installations by the architect at the same site.
The walkway is the most recent project designed by Glenn Howells Architects at the Arboretum. The practice was responsible for a new masterplan of the site and has designed an elegant timber pavilion with a curved roof, the Welcome Building, at the main entrance (subject of a TRADA Case Study in June 2015).
More recently, in the ‘working’ part of the estate, a pair of innovative new timber buildings designed by Invisible Studio have just been completed (described in detail in a TRADA Case Study in March 2017). The structural engineer BuroHappold Engineering was part of the design team for all three projects.
Reflecting the treescape setting of the surrounding natural landscape, timber was the obvious choice of material for the project and was at the heart of the architectural concept developed by the design team. The walkway structure, deck and guardrails are predominantly constructed of timber.
The walkway was designed to be as elegant and sustainable as possible within the constraints of the budget. The walkway deck is supported by a series of timber columns, set in pairs and canted across each other like a pair of scissors, to mimic the lean and sway of surrounding tree trunks.
The pairs of columns are set apart at 10.75 metre centres and the pairs vary considerably in length, depending on the terrain below.
The walkway structure, which curves to accommodate tree roots, consists of a pair of RHS outer members set at 1500mm centres with secondary steel beams welded between them. The canted balustrades on each side, a series of 15 x 50mm galvanized steel flats set apart at approximately 100mm centres (depending on the curve of the walkway), are welded to steel plates welded back to the RHS members. The balustrade is topped with a solid larch handrail.
Larch was selected as the principal material for the walkway, both for its durability and attractive colour, with Scottish larch chosen for the deck and handrail. The larch, it is anticipated, will weather to silvery tones, which will match the galvanized steel balusters which support it. The columns, meanwhile, are of solid Siberian larch.
Commenting on the Walkway, the 2016 Wood Award judges said: “This structure has the ability to inspire all generations to learn more about wood.” Click here to read why.
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