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    Multi-storey timber buildings: A renaissance in timber construction

    Dr Fred Moshiri

    The ever-increasing range of engineered wood products and systems is generating global interest and drive for greater innovation in new on-site and prefabricated building solutions. At the same time, more people are realising the benefits of timber construction for multi-storey buildings, causing a resurgence in its use.

    The use of timber in multi-storey residential and commercial buildings is not something new. It has a relatively long history and in fact, it was one of the only choices available in Australia up until the early 20th Century. This can be observed from the number of permanent timber structures such as existing industrial warehouses from the 1800s and residential buildings. The popularity of timber construction at this time can be attributed to the widespread availability of both high-quality native hardwoods and framing material manufactured by softwood plantations.

    MODERN CONSTRUCTION

    Engineered wood products such as cross-laminated timber (CLT); laminated veneer lumber (LVL); glue laminated timber (glulam); plywood; and laminated strand lumber are now available in a wide variety of thicknesses, sizes and grades, and have a wide range of applications as structural materials in construction. These products are manufactured from veneers, strands or flakes to meet application-specific performance requirements. These manufactured components are bonded together utilising adhesives under heat pressure to form value added structural members, making them an attractive option for construction.

    There is currently a growing list of multi-storey heavy timber and timber hybrid buildings being constructed in Australia and across the globe. These buildings are pushing the boundaries of technology, utilising engineered timber products and timber composite structural systems.

    For example, the 9-storey Stadthaus Building in Hackney, built in the UK in 2009 has been the first major high-rise residential building to be built from pre-fabricated load-bearing walls and floor cross-laminated timber panels (CLT). The stair and lift cores have been also entirely built in CLT.

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    Stadthaus Building, UK. Image: Will Pryce

    Standing at 32.2m, the Forte building, a 10-storey CLT residential complex in Melbourne, completed by Lendlease in 2012 is the first Australian building to be made from CLT.  

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    Forte Living, Melbourne, Australia. Image: Imagecontrol.com.au

    Worldwide interest in timber engineering and modular volumetric prefabrication goes on, with a 14-storey building completed in Norway utilising 3D volumetric prefabricated modules and the world’s tallest hybrid timber residential building, the 18-storey UBC Brock Commons student accommodation residential tower in Vancouver, Canada. This building comprises glulam columns and CLT floors and 2 concrete lift cores.

    Taller buildings are also planned, including the 24-storey HoHo tower in Vienna, Austria, and a 34-storey residential tower planned in Stockholm.

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    34-storey timber skyscraper for Stockholm. Image: C.F. Møller Architects

    KEY DRIVERS AND FACTS

    There are many reasons for timber’s resurgence, but key market drivers include strong international demand for low- to medium-rise residential and commercial buildings due to demographic changes; demand for sustainable design and Green Building annotation through the use of environmentally sustainable materials which are renewable, recyclable and carbon-friendly; and low embodied energy.

    Off-site prefabrication and integrated construction of timber buildings can reduce construction programs significantly. Other benefits include:

    • Buildings can be disassembled and relocated at the end-of-life.
    • Reduced site labour, lower environmental nuisance and disruption to local residents.
    • Reduced weight of the overall building as timber is around a fifth of the weight of concrete. Consequently, timber buildings can weigh 50 percent less than a traditional reinforced concrete building, which makes timber a favourite in restrained construction sites with limited space.
    • Decreased dead-load on the foundations which greatly reduces the construction cost, particularly in sites with pour ground condition.
    • More architectural design flexibility offers more design options without sacrificing structural requirements.
    • The natural warmth and timeless beauty of the timber structure provides a structural system and a decorative feature in the one element.

    Moreover, new studies show that timber buildings cost less to construct compared to conventional buildings such as steel and reinforced concrete. For example, Commercial Building Costing Cases Studies – Traditional Design versus Timber Project by the Timber Development Association for Forestry and Wood Products Australia demonstrated that timber buildings would be 10-15 percent more cost-effective to construct compared to other conventional construction methods. For example:

    • Commercial office building: -12.4 percent
    • Aged care facility: -13.9 percent
    • Apartment building: -2.2 percent
    • Portal-framed industrial shed: -9.4 percent

    OTHER FACTORS

    The health and wellbeing benefits of timber construction and interiors in homes, businesses and educational facilities and hospitals are well investigated. Knowing that Australians generally spend 90 percent of their time indoors, the quality and character of the indoor environment has a great influence on the wellbeing of occupants.

    Timber and wood also contribute naturally to moderate humidity by absorbing air moisture when the humidity in a space is high, and releasing it when the humidity is low. This moisture-buffering minimises the impact of pathogens and chemical interactions on human health.

    Some studies such as Planet Ark’s Wood – Housing, Health, Humanity Report have also found that timber and wood product have a significant de-stressing effect and enhance psychological well-being of occupants. The warm inviting feel from wood and timber decreases blood pressure, heart rates and anxiety, according to the study.

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    The Cabin, Mount Wilson. Designed by SJB Architects, structural engineering by ACOR Consulting. Image: Charles Peters

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    30 Murrain Street, designed by Thodey Design structural engineering by ACOR Consulting. Image: ACOR

    CHALLENGES

    The shift away from concrete and steel towards timber in Australia’s multi-storey residential and commercial buildings is not without its challenges. Steel and concrete products are well-established and accepted in the Australian market by designers, contractors and developers, for example. Moreover, it is essential to have an alignment between forestry and the supply chain, as well as the Australian timber industry’s ability to respond to the demand of manufacturing and fabricating building elements required for the construction of multi-storey residential and commercial timber buildings. 

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    acor5.jpgDr Fred Moshiri is a senior structural engineer at ACOR. He has 10 years of experience in R&D, design and construction management of residential and non-residential projects, and has worked at the forefront of developing massive timber buildings in Australia. He has expertise in timber and composite engineering from 10 years of work in developing timber information for the European and Australian timber industry.

    ACOR Consultants is an Australian-owned company with teams that provide specialist services for civil and structural engineering, building diagnostics and BIM, fuel/petrochemical, dangerous goods and MEPS services. ACOR’s expertise in timber engineering has been commissioned for residential and non-residential developments constructed utilising cross laminated timber, glue laminated timber and European made connections.

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