Whole Timber Construction: A State of the Art Review

Forests worldwide are overstocked with small-diameter trees, putting them at increased risk of disease, insect attack, and destructive high-intensity wildfires. This overstocking is caused primarily by the low market value of these small-diameter trees, which are generally unsuitable for sawn timber production and yield low prices when sold for biomass fuel, paper, or fibre-based engineered timber products. Considerable research in recent decades has demonstrated the potential for these small-diameter trees to be used in minimally processed round segments as structural elements in buildings, bridges, towers, and other infrastructure. Recent structures have also demonstrated the use of trees with major curvature and branching, which are also of low market value, in their round form as primary structural elements. Such “whole timber” construction serves as a low-cost, low-impact building system while providing revenue to forest owners to conduct harvests of low-value trees as required for sustainable forest management. This paper reviews developments in whole timber construction, presenting new non-destructive evaluation techniques, digital survey, design and fabrication methods, new processing technologies, and a diverse range of novel connection types and structural systems. It is shown that the key materials characterisation, processing, and design challenges for whole timber construction have been largely addressed, and that whole timber has the potential to be an important complement to other timber products in construction globally in the coming decades. It is recommended that future work focus on exploiting new digital technologies and scaling whole timber structural applications through increased prefabrication.