How wood is trending as a renewable building material, even for high-rises - but don't expect timber skyscrapers in Hong Kong

By Peta Tomlinson / | April 28, 2020 12:09 PM SGT
In some cities around the world, timber is making a comeback as a more sustainable, cost-effective construction material of choice " even for high-rise buildings.
The 52-metre (170-foot) tall office building at 25 King Street in Brisbane, Australia, designed by architecture firm Bates Smart, was the tallest timber tower of its type when completed in 2018, surpassed last year by the 84.5-metre Mjostarnet in Norway, by architect Voll Arkitekter.
One of Asia's largest, slated for completion in 2021, is the six-storey, 28.75-metre new home of the business school of Nanyang Technological University (NTU) in Singapore. And in Tokyo, timber company Sumitomo Forestry is planning a 70-storey, 350-metre timber tower, although it won't be completed until 2041.
There are scant examples in Hong Kong, the city with the most high-rise buildings in the world, as current building codes make building with timber too challenging for developers to attempt. The problem, explains Otto Ng, design director of LAAB, is the lack of guidelines to facilitate the use of timber as a material for any structure or facade above 6 metres high.
Otto Ng, design director of LAAB. alt=Otto Ng, design director of LAAB.
"This doesn't mean that it's not allowed," he says. "You can still submit a timber structure or facade [proposal] for the Buildings Department's review and approval. However, you may need to tackle unprecedented challenges such as laboratory tests that would take years " and cost a lot. Therefore, nobody would ever try it."
Ng says that Hong Kong building codes have not kept pace with timber technology. He believes the conversation around its use should be reignited, and feels the architecture fraternity would support this. "Aesthetically, timber has its own character, but more important is sustainability," Ng says. "Timber is generally lighter than steel, concrete and glass; it's renewable [as forests can regrow], and offers more design opportunities."
Mjostarnet in Norway, by Voll Arkitekter, is the tallest timber tower at 84.5 metres. Photo: Voll Arkitekter alt=Mjostarnet in Norway, by Voll Arkitekter, is the tallest timber tower at 84.5 metres. Photo: Voll Arkitekter
LAAB's creative interpretation of the material is expressed in a food kiosk completed last year at the Avenue of Stars on Tsim Sha Tsui's promenade. Because it was designed to move, the kinetic architecture Ng envisaged called for a material as light as possible. He also wanted it to look natural, as if an extension of Salisbury Garden was behind it. After considering different materials, including stainless steel, bamboo and wood, the design team settled on red balau for the 5.9-metre building.
That choice of timber constitutes a sustainable facade material because of its strength, hardness, lightness and cost-effectiveness, Ng says. Supported by 49 connected robotic arms that provide the mechanical movement, the timber is fashioned as "fins" made using digital fabrication and finished for durability with exterior grade oil.
"We needed to dry the wood very carefully throughout the preparation process," Ng says. Because wood is natural, with no identical pieces, the fabrication process is more complicated. Re-application of oil regularly is also needed to fight against potential shrinkage, swelling, deterioration, moisture and termites.
Prefabricated cross-laminated timber construction can replace traditional steel and concrete for low- to mid-rise commercial office buildings. Photo: Tom Roe alt=Prefabricated cross-laminated timber construction can replace traditional steel and concrete for low- to mid-rise commercial office buildings. Photo: Tom Roe
LAAB's design, titled Harbour Kiosk, was shortlisted for the World Architecture Festival's Best Use of Certified Timber Prize 2019.
While LAAB's kiosk was a one-off project, Mass Engineered Timber (MET), an umbrella term encompassing various wood products engineered to have improved structural integrity, is hailed as a hero material for mass construction in cities.
Serena Yap, Built Environment Unit leader at Aurecon, an international engineering, design and advisory company whose Brisbane base is at 25 King Street, says timber can be installed quickly and efficiently using modular construction methods.
"In terms of strength-to-weight ratio, MET is lighter than steel and concrete and, therefore, easier to handle and lift " so on an average construction site, both the number of people and the time taken to complete the project can be reduced by around 30 per cent," she says. "You won't need cranes that are as big and powerful as you would for steel and concrete, and the pieces of timber are designed to be slotted into each other quickly."
With fewer workers needed on site, it creates a safer and quieter environment, Yap says.
Even in areas prone to high humidity, she says, because the timber is treated, moisture is not an issue.
There are many classes of MET, depending on the usage or location, according to Yap: for example, designers might choose spruce for interior use, and a timber such as larch for exterior facades, while different types of laminates can be used to give additional protection as needed.
In Rethinking Timber Buildings, a report released last year, global engineering, architecture and planning company Arup also endorsed the case for architects, developers, planners and corporate organisations to consider mass timber when designing low and mid-rise buildings.
Describing timber as the only 100 per cent renewable building material, Andrew Lawrence, global timber specialist at Arup, wrote: "New technology means that a timber building can now be assembled incredibly fast, making it a viable option for an increasing number of projects."
Edmund Tong Kin-wah, director for business development at SCA, a company selling timber products in China and Southeast Asia, also sees a groundswell of opinion pushing for change in Hong Kong. With cities "everywhere in the world promoting use of timber for building construction", he can't understand why Hong Kong isn't.
"People in Hong Kong are really frustrated," Tong says. "I know a lot of architects and designers want to use wood " they have seen it in other parts of the world [and are asking], why not Hong Kong?
"In olden times [in China], we used wood for houses and temples. Some temples have lasted more than 1,000 years. In high-rise buildings all over the world " including some in northern parts of China " glue laminated beams [known as glulam] combined with cross-laminated timber [CLT] are used for the walls, flooring and columns. With proper use of selected wood and fabrication, this laminated material can be stronger than steel."
Tong also believes many people today would prefer to live in wooden houses. He feels that New Territories villages with open space around them, such as in Sai Kung, would be ideal locations to get the ball rolling in Hong Kong.
"We can start from there " not with high-rise towers, but three-storey houses," he says.
Designing tall timber buildings does require a different approach, and since it's difficult to make adjustments on site, the details must be finalised ahead of construction. Yet Bates Smart architect Philip Vivian, the project director for 25 King, says this project proves it can be done " "that prefabricated CLT construction can replace traditional steel and concrete for low- to mid-rise commercial office buildings".
This article originally appeared in the South China Morning Post (SCMP), the most authoritative voice reporting on China and Asia for more than a century. For more SCMP stories, please explore the SCMP app or visit the SCMP's Facebook and Twitter pages. Copyright © 2020 South China Morning Post Publishers Ltd. All rights reserved.
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