Let the experts decide the best building material for the job

23 June 2020

While the post Covid-19 economy will require timely and bold Government intervention, demanding timber be considered over other construction materials could compromise the resilience and safety of our homes, places of work and infrastructure.

While well-intentioned, a potential ‘wood-first’ policy dictating that all new government buildings up to 10 storeys consider a timber option, and that government give preference to renting new timber buildings, will have serious unintended consequences.

This policy proposal has been around-the-houses for over a decade. In 2014 the then Economic Development Minister Steven Joyce referred to it as “classic 70s ‘government knows best’ interventionism” and wryly asked ;”What next, supplementary minimum prices for wood?”

As we begin to grapple with the aftermath of Covid-19, timber industry advocates have been quick to bang this misconceived policy drum, praising it as a silver bullet to address looming unemployment, while exaggerating the properties of structural timber along with its sustainability credentials.

What is required now more than ever, are well thought through strategies which, from a construction perspective, look to expand the housing stock and address the infrastructure gap while respecting our carbon zero aspirations.

To start arbitrarily stipulating one building material over another will harm rather than help the economy, the environment and ultimately New Zealand. Let those most qualified make the decisions on building materials.


Government procurement favouring wood in new buildings will draw out the fundamental step in the construction process of selecting materials based on proven performance.

The potential policy disrespects and undermines the technical expertise of structural engineers, architects, quantity surveyors and contractors. These people are best placed to determine the most suitable building materials based on a project’s requirements and commercial expectation.

It is also a duplication of effort to mandate that experts must consider wood alongside other materials, such as concrete or steel, when they are more fit for purpose. This will inevitably cause project delays and drive up construction costs.

While discussion around the merits of new building technologies is healthy, the actual uptake of new technologies must be based on sound evidence.

Therefore, it is alarming to see the enthusiasm with which cross-laminated timber (CLT) is being greeted by some, despite serious questions asked internationally of how it will perform in a fire. Research has indicated the potential for CLT to delaminate under extreme heat and contribute to fire growth.

Furthermore, New Zealand building standards do not yet contain provisions for engineered wood products such as CLT, and a capable practitioner base does not yet exist to support designing with these new technologies. With the many technical and financial obstacles to the widespread acceptance of CLT, including insufficient knowledge of its short and long-term performance, you have to wonder why the policy is even being proposed.


The potential policy also does a huge dis-service to the hardworking men and women in the wider aggregates, concrete and metal industries, which operate facilities all over New Zealand, from Kaitaia to Invercargill, and employ close to 40,000 people.

Favouring a single construction material could seriously impact on their livelihoods and jobs. The vague possibility of job creation in one industry must not come at the expense of another industry. If the timber industry is struggling, not just as a result of Covid-19, Government policy must not be the fallback option.

To claim that ‘wood-first’ will help employment in the regions, as some in the timber industry have, when in fact the opposite could be true, makes no sense.

It must also be noted that currently there is only a limited amount of engineered timber products manufactured here in New Zealand. The bulk, like CLT, is imported from either Australia or Europe, which is not creating any New Zealand jobs, and is only adding to timber’s carbon footprint.

This is very different to our concrete and steel industries, where the majority of the concrete and steel used in New Zealand construction is manufactured in New Zealand.


To claim that a wood-first policy will have better environmental outcomes is fundamentally flawed.

A complete ‘cradle-to-grave’ life-cycle assessment is required to compare the environmental impacts of building materials. It is important that an assessment covers all stages of a building material’s life cycle, and that robust science and independent data are used to assess a building’s carbon footprint.

A full assessment will include considering the materials selected, transportation factors, the construction process, the building’s use, and the end-of-life recycling and disposal stages. While important, embodied carbon is not the only metric in evaluating a building’s environmental impact.

Over recent decades the concrete industry has been aware of its environmental impact, innovating with new ways to reduce emissions, minimise waste and increase recycling. From 2005 to 2018, CO2 emissions associated with cement clinker in New Zealand dropped by 15 per cent, despite a 13 per cent increase in concrete production — an achievement the industry is extremely proud of.

This was accomplished through replacing cement with ‘supplementary cementitious materials’ (industrial by-products), substituting a percentage of coal with wood biofuel in the manufacture of cement, and a general shift to more efficient manufacturing. The concrete industry has made significant progress on its journey to decarbonise.

Most excitingly of all, New Zealand is now exploring options for the use of volcanic ash from the North Island’s Central Plateau as a low-carbon cement replacement. Referred to as pozzolans, after the Italian city of Pozzuoli, these naturally occurring materials offer a stable local supply, and should be cost competitive with ordinary Portland cement. Join Registered Master Builders CEO David Kelly for a live Q&A on Stuff on Friday


The New Zealand construction sector has demonstrated its resilience over the past decade or so, rebuilding after the leaky building crisis, global financial crisis and the Canterbury earthquakes. Now we find ourselves redefining how the construction sector will operate in the wake of Covid-19 and with the aim to be carbon zero by 2050.

It is no time for a misinformed policy to come into force that will favour a single construction material.

The last thing we want is another leaky building debacle — or worse.

Leave the selection of fit for purpose building materials to those that are most qualified — our architects, structural engineers, quantity surveyors and contractors — respecting New Zealand’s existing capability and resources.

Feature Image: Rob Gaimster is chief executive of Concrete New Zealand

Source: Stuff News

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