Learning from Trees

Entrant: 
Andrew Barrie Lab

Category: 
11. Innovative timber manufacturing & technology award

Photographed by: 
Marcela Grassi / Mark Smith

This project was an invited exhibit within the Italian Pavilion at the 17th International Architecture Exhibition of La Biennale di Venezia. The brief called for a meeting and display space that both showcased the innovative use of timber, and our intention for the project was a lightweight, sustainable structure pointing the way to a different kind of timber construction.

The project budget was small, and the structure was required to be repeatedly assembled and disassembled. To achieve this, the project relied on two key kinds of innovation for fabrication – a cunning diagonal geometry that created visual intricacy but reduced structural complexity, and developing a means to cheaply and accurately mill thin, non-orthogonal timber elements.

A major challenge when designing timber structures is that the joints are often reliant on steel fixings to transmit loads and allow ductility. What begins as a largely timber structure can quickly become dominated by steel plates to make the joints function. This type of construction is expensive and complicated, negating the sustainability, economy, and ease of construction that are the great benefits of timber. Further, in complex timber structures, particularly those following non-orthogonal geometries, joints and corners often become geometrically complex and difficult to build. The solution developed for this project is not to ‘fold’ the structure around the form, but consider the structure as three-dimensional at the outset. The structure is formed with simple, repetitive diagonal frames adjusted to the width required at each position. This means the joints become very straightforward and ‘seamless’, and can be resolved with simple steel L-plates largely hidden within the timber.

The diagonal geometry results in timber structural elements with diamond-shaped profiles. In effect, diagonal geometry transfers technological and manufacturing complexity from steel joints (difficult, expensive and ugly) to timber profiles (easy, fast, and pretty). In addition, by embedding hidden symmetries into the overall geometry, the number of different timber profiles and joint types required was halved. In recent years, staff and students [at a NZ university] have devised a ‘hack’ methodology for efficiently modeling and milling timber structural elements en masse using standard CNC machines.

This involves digital processes for modelling elements and preparing cutting files, as well as the development of a jig system that allows elements—including elements much bigger than these relatively small machines are intended to accommodate—to rapidly be secured in the milling machine, milled, and removed for assembly. The specific challenge with this project was to mill profiles that would not rest on a flat surface. We developed custom jigs that accurately positioned and supported the profiles, allowing a dozen elements to be milled every hour.

The timber used was Abodo screening, a thermally-modified pine product, chosen for its stability—a key attribute, given that the structure required of 1.2kms of timber elements custom milled with joints every 200mm (on average) along their length.

The guiding technological principle for this project—rather than create complexity, make difficult things simple—produced a seamless, lattice-like structure recalling the intricacy of a woven basket.