SALCEY TREETOP WALK, NORTHAMPTONSHIRE
To recognise a project that demonstrates a particular contribution to environmental issues or in which environmental issues and/or sustainability were a key factor in its concept and/or execution. Sponsored by Atkins.
The object of the treetop walk was to create a free-to-use experience to enthuse the public, and particularly children, about trees and forests while employing the maximum possible proportion of sustainable materials in construction.
Having obtained a grant, the Forestry Commission (FC) engineers set out to build as great a length, and height, of walk as possible for the money available. The concept developed into an all-timber low-level causeway, made entirely with wood from the FC's nearby forests, linked to a high-level gangway ramping up to 15m high, built from a mix of timber and off-the-shelf steel components. The walkway leads up to a 20m-high lookout tower.
Stiff steel tubes form the legs of the high-level towers to ensure stability with a minimum of cross-brace latticing, which would have clashed with the predominant vertical structures of the adjacent tree trunks. Off-the-peg steel-tube lattice aerial masts have been employed as low-cost main beams spanning between the towers. Adjacent spans are all set out at an angle at each tower to ensure overall stability of the walkway, with the individual spans deliberately designed to give a lively dynamic response for the enjoyment of users.
The slatted deck and handrails are entirely of treated but unpainted local timber, which should require a minimum of maintenance since they do not retain any standing water and are exposed so that rain will dry off rapidly.
Included as part of the walkway is a demonstration stress-laminated timber bridge and stress-laminated roof structure, claimed to be a first. These employ small timber sections, such as could be harvested from young trees, cramped together to form relatively large arch spans.
Client Forestry Commission Cost £700,000 Principal designer Dr Geoff Freedman Contractor Pauley Construction