Materials Matter
The Southern Lakes Better Building Working Group kicked off 2025 with two back-to-back events on 5 March. A Builders Brekkie followed by an evening Better Builders Banter.
Both events showcased amazing venues. The Brekkie took place at LMA Timber’s new showroom on Anderson Rd in Wānaka, which boasts an amazing interior full of beautiful Australian hardwoods and other reclaimed and sustainable timber.
The evening Banter session at the Architecture + Design Library also allowed participants to check out the shared working space and display of amazing local interior design and architecture options.
With a common theme of sustainable building, attendees learned of the current issues facing the building industry in terms of construction and demolition waste, recycling and reuse practices, and sustainable building materials.
Shana Payne of Designgroup Stapleton Elliot and the Southern Branch Chair for NZIA opened the Better Building Banter session at the AD Library. She provided a succinct overview of the circular economy and why building sustainably is important, as well as outlining the challenges the sector faces in driving change.
While monetary cost is constantly at the forefront of nearly everything we do, particularly when it comes to building, it's easy to forget other types of costs. Hamish McPhail of Salmond Architecture drove the point home by explaining that both ethical and environmental costs are also at play.
Not only is it important to consider what damage certain building materials may have on our environment, our health, or the people and places where they come from, but also the longevity of such products. A huge unanswered question mark floated over the room of why New Zealand building practices only looks at 50 years for a lifetime of a building. As one participant said "look at Europe, they build in terms of centuries...why don't we?"
While speculation to our particular weather and environmental conditions here in New Zealand floated to the surface, it became apparently unsatisfactory as products such as LMA Timber exist and are locally available, that are not only reclaimed from things such as old telephone poles but also hold a much longer lifetime compared to a lot of other products you typically see homes built with.
When considering cladding for a home, the full lifecycle of a product is often discounted or not considered. While it may seem like a good idea to build with cheaper cladding, when looking beyond 50 years there tends to be additional costs not previously looked into.
McPhail managed to put together renderings of an example home and applied different cladding materials to it. He looked at corrugated metal, pine weatherboards H3.2 with CCA treatment, thermally modified timber cladding, and spotted gum.
Corrugated metal was by far the least expensive option, but it holds extremely high embodied carbon and likely needs complete replacement after 50 years. Due to the concerns around carbon, which is something the building industry has been looking at regulating for some time now, timber becomes the likely choice as it is often carbon negative.
While there are quite a few different timber options out there, McPhail's presentation provided excellent insight into several options and their costs.
Participants were surprised to hear that pine weatherboards with CCA treatment (Chromated Copper Arsenate treatment), a common NZ timber cladding, is banned in places like Australia, the USA, and the EU due to arsenic poisoning. Not only is it bad for the environment as it needs to be buried in our landfills at the end of it's life rather than be recycled or mulched, but it's claimed lifespan is also only 20-30 years.
So, when looking at this type of timber as cladding, not only are you negatively impacting the environment, but over the buildings 50 year lifetime, you would need to replace the cladding at least once. It also includes more frequent maintenance fees for suggested oiling, thus bringing significant replacement and maintenance costs to the table.
On the other hand, spotted gum (an Australian hardwood available from LMA Timber) came up with the highest upfront costs. However, due to it's extreme durability, the lifetime of the product is much longer than other timbers (40-50+ years) thus significantly reducing maintenance costs and being better for the environment, especially when it's sustainably reclaimed.
By McPhails calculations, after 50 years, the spotted gum was the cheaper of the three timber cladding options by over $20k, even with the higher upfront costs.
The Southern Lakes Better Building Working Group (BBWG) has 3 main focuses:
Circular Economy
Reduction of Novel Entities/Toxicity of Materials
Climate Smart and Resilient Building
When looking to build sustainably, it’s important to consider these three factors.
Build with the idea of eliminating and reducing waste. Consider reuse, both at the start and for the end of a project. “Screws not Glues” is an excellent reference.
NZ should be looking hard at what materials we are using in our homes. For example, should we really be using CCA treated timber to save a buck? We need to consider building healthy homes, not toxic boxes.
Lastly, we should be looking to build for the long term. Building to a 50 year lifetime is not only uneconomical, but also unsustainable.
To find out more about the BBWG and keep up to speed with any other upcoming events, visit www.wao.co.nz/better-building
Links to the presentations:
