Rethinking laminated timber solutions: adding economic value to underutilised resources

The timber we've overlooked could be the key to a more sustainable future for construction.

That's the ethos of two ongoing research projects in the Structural Timber Innovation Laboratory at the University of Auckland.

Professor of Architecture Anthony Hōete is investigating the potential of structural laminated native tōtara and Dr Gary Raftery, a research director in the Circular Innovations Research Centre, is examining the manufacture of engineered wood using secondary timber from demolished buildings.

The thinking is that these underutilised resources could be transformed into higher-value laminated engineered wood products and support New Zealand’s transition towards more resource-conscious construction.

Exploring the potential of tōtara and kahikatea

Professor Anthony Hōete is exploring how laminating native tōtara and kahikatea could create new applications for a species with significant cultural, architectural and material qualities.

Tōtara, for example, has a number of characteristics that make it particularly interesting for contemporary construction. It has exceptional natural durability and dimensional stability, is slightly denser than pine, and develops a protective char layer during fire.

Rather than considering timber only in its conventional solid form, lamination offers an opportunity to reconfigure smaller or otherwise underutilised pieces of wood into larger engineered components.

Individual pieces can be assembled and bonded to produce structural or architectural elements with dimensions and properties that may not be achievable from a single piece of timber.

Hōete is testing the approach using 8m curved beams fabricated by his team in the architecture workshop. The work is supported by Ngāti Ira o Waioweka and MBIE’s Vision Mātauranga Capability Fund: Carving New Knowledge in Construction Technology.

For Hōete, the research provides an opportunity to rethink how native timbers can be sustainably incorporated into contemporary timber construction, while considering how the characteristics of the species can inform new applications.

The work forms part of a wider interest in how New Zealand's timber resources might be used more innovatively, particularly where conventional approaches do not capture the full potential of the material.  

Giving salvaged timber a new life

Dr Gary Raftery is looking at a very different source of timber – wood that has already been part of a building and that is usually landfilled.

Raftery, a research director of the Circular Innovations Research Centre, is spearheading research into whether timber recovered from demolished and refurbished buildings could be given a new life as engineered wood products, including glued laminated timber.

Every demolition or refurbishment project can generate large quantities of timber. It can be difficult to directly reuse all pieces in conventional construction as recovered wood comes with a history: its species, dimensions, condition and previous use can vary considerably.

Raftery is exploring whether lamination could offer another way to use it.

Instead of requiring every piece of recovered timber to meet the same specifications, individual pieces can be assessed during the remanufacture process. Defective or contaminated material can be removed, while suitable timber can be bonded together to create engineered components.

"Lamination of the resource using adhesives poses technical challenges, but also opens new opportunities where the uncertainty associated with the material can be limited," he says.

In other words, the process could turn a variable and sometimes difficult waste stream into a more consistent feedstock for new construction products.

For Raftery, that requires a change in how we see demolition timber.

"The research involves rethinking timber at the end-of-life not as a waste stream, but as a potentially valuable secondary resource and carbon store," he says.  

Moving towards resource-conscious construction

The thinking behind both projects is simple: there may be opportunities to get more from the timber resources we already have. That matters in a construction sector looking to reduce material waste and the environmental impact of buildings.

As New Zealand targets net-zero goals and moves towards low-carbon design, including the use of mass timber in mid-rise construction, there is growing pressure to make better use of resources already in circulation.

It also means looking beyond the conventional hierarchy of timber use. A piece of wood that isn't suitable for one application isn't necessarily without value. With the right processing, design and engineering, it could become part of something new.

That is the more resource-conscious approach to construction the two projects are exploring – there may be more value in the timber resources that are available to us.