Timber, a material with a bundle of challenges, all worth it

The Fifth Estate last week moderated a panel on timber at an event at timber 25 King Street, Brisbane, the 10-storey timber office building. The event was organised by Bates Smart and Aurecon as part of the Brisbane Open House program. The following is a report based on interviews ahead of the event and on comments during the discussions on the night.

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Last week’s event on timber at 25 King Street in Brisbane was one for the books. An almost full house, mostly architects, replete with in-depth questions that at one stage looked like would keep going until midnight.

The audience had come to find out more about the venue they were in – at 10 storeys, it’s believed to be the tallest timber office building in Australia, if not the world – designed by Bates Smart, for developer Lendlease and lead tenant and engineer for the project Aurecon.

Such intense interest in a building material is unusual, to say the least. But timber, of course, doesn’t rate as just any material; it’s special in any number of ways.

Panellists:

• Dr Paola Leardini, senior lecturer, School of Architecture at University of Queensland and expert on building technology, building performance and occupancy comfort
• Philip Vivian, director of Bates Smart and lead design architect for 25 King Street
• Josephine MacLeod, principal advisor – Architecture & Urban Design, Office of QLD Government Architect
• Chris Ammundsen, senior structural engineer and timber expert at Aurecon (part of 25 King Street project team)

Bates Smart Architects director Philip Vivian told the audience that he’s observed some rather interesting behaviour around the site during and after construction.

Notice how even tonight, he said, some people came in and instinctively wanted to touch the timber, feel its texture. He’s heard some people joke that they feel like hugging the huge square columns that are as thick as giant trees in the forest.

During construction, the site was calm and quiet, he told the audience. Absent was not just the noisy clanging and screeching of machinery and tools of regular building sites, but the (typically) bawdy jiving and carving of graffiti into the walls and floors.

Well, with eight rather than a more typical 80 workers on site, numbers might be one reason for the differences. Another is that the construction process itself is quiet. Not much banging and drilling needed, mostly careful positioning and screwing of precisely engineered components.

Questions from the floor were revealing

Curiosity about fire was kept right to the end. For regular audiences (lay people) timber industry insiders say it’s pretty much the first and most urgent focus of attention.

But this more informed cohort knew that, as Aurecon’s Chris Ammundsen put it, anyone who’s experienced a campfire knows that throwing a big log onto the coals inevitably puts them out. Fire needs to breathe. Besides, he said, there is typically a sacrificial layer on the exterior that will take the flames while protecting the structural part of the building underneath.

Of more interest on the night was the need in this warm and often moist climate of Australia’s north to protect against moisture and mould in timber buildings.

Around Australia, there is an emerging problem with mould and poor ventilation in buildings causing significant health problems.

It’s one of the key areas of investigation at the Future Timber Hub at the University of Queensland, according to Dr Paola Leardini, who is also chief investigator at the hub. Other members include Lendlease, Arup, Hine, fire authorities, academics.

“In a hot humid climate, moisture is the biggest challenge and the glues used in CLT tend to react in different ways,” she said ahead of the event and elaborating on the night.

“We’re starting to research that aspect: How much can timber help to buffer the humidity of the environment?

“Most important is the question of do we build in the same way as in Europe or Melbourne? Where do you put the insulation, and how do you treat the moisture?”

One possibility is that in hotter, more humid climates, membranes and insulation might need to be on the outside of the building. The research, though, is still in its early days. (At 25 King Street, Ammundsen explained a technical solution was found through the choice and structure of the façade.)

Of course, anything new is typically viewed with suspicion by the generally conservative building and construction sector, until its members see prototypes in action.

Ammundsen, Vivian and the timber industry sources in the audience on the night agreed there was growing interest in timber and huge promises for this renewable resource.

The benefits can be economic

Embodied carbon, carbon sequestration and biophilic benefits of timber are well known but according to Leardini potential is also for the industry to lend some economic and employment strength to an economy that needs to transition away from fossil fuel dependence and materials that rely on huge carbon emissions. There was a study underway at the University of Melbourne to put some numbers to what that might look like, she said.

In Brisbane, timber was a natural material and very much part of the vernacular in housing, said Josephine MacLeod from the Government Architects Office.

It was loved for its greater affordability in the early days and for its ease of construction amid the city’s rolling hills. Today the classic timber Queenslander has also helped efforts to densify sprawling suburbs. These houses have proved quite easy to move to entirely new locations or even to the side of a block to make way for townhouses.

Timber might also be useful for the so-called Missing Middle, the program to densify Australia’s sprawling suburbs with sensitive infill.

MacLeod said an affordable housing demonstration project in timber currently underway by Queensland Housing and Public Works could demonstrate some leadership for the sector.

“The government is not typically innovative,” MacLeod said, but that is needed now; “it takes a champion (to get traction).”

It was about showing that “the government is leading by example rather than expecting everyone else to lead.”

Cost

Among the challenges, especially for leaders, or pioneers in any venture, is cost.

“You need to understand the costing. It’s not like a traditional building where you know all the costs. There are a lot of fire regulations that need to be worked around,” MacLeod said.

“You also need supplier involvement to understand the detailing and to understand even what the costing is.”

According to Vivian, although the the timber initially costs more, “that’s not the end of the story.”

“You spend more on the material but less on the time to construct it. And on labour.”

The final cost of 25 King Street cost is unknown, partly because of the complicated arrangements that come when the head tenant is also a major consultant on the project.

Ammundsen said “it probably did cost a bit but we felt it was worth it; 6 per cent more was mentioned in early stages of design.” The final figure remains a mystery. Though Vivian says his studio stuck to its agreement with Lendlease to deliver the final design at exactly the same price as a conventional building.

A project at Monterey 

There’s another view of cost, says Ammundsen. You might want to look at an apartment building at Lambert Street at Monterey Kangaroo Point developed by the Gardner Vaughan Group that managed to achieve a 10-storey building in timber, while in steel and concrete the extra load would have only permitted a six-storey building.

What’s the limit?

For Vivian, the best possibility for timber is mid-rise and more so in residential.

Mainly this is because of timber’s lesser spans compared with concrete and steel and the preference in offices for big open plan floors (for now; fashions might change and a preference emerge for friendlier team-based hubs in office.)

A 21-storey office building has been “engineered” Vivian said, but with the hybrid option of concrete floors. “Above that, there’s a diminishing opportunity for timber. It’s a mid-rise material.”

Ammundsen says future lies in buildings between 6 and 15 storeys.

And as for fire, MacLeod proves its viability by pointing to a two-storey fire station that’s been designed at Maryborough, in timber, with architect Kim Baber the architect. The building is still at the concept stage but you get the idea.

The Fifth Estate travelled to Brisbane and stayed one night as a guest of Bates Smart.