Timber, steel and concrete are three of the most common structural materials in the world, and each material has pros and cons. We asked industry bodies representing each to argue their case.
Timber has higher structural efficiency as carried load per unit weight compared to reinforced concrete and steel structures. A common stud used in house construction has similar compressive strength to general purpose concrete. Many timbers are either naturally durable or can be easily treated to make very durable. Wood, the raw material of structural timber products, is made from energy from the sun and carbon absorbed from the air (from the carbon dioxide in the air). Half the dry mass of timber is carbon absorbed from the air. Timber used internally provides a healthier environment for occupants as it helps maintain a better relative humidity. The vast majority of structural timber is sourced from sustainably managed forests and plantations.
“Concrete has been used for structures since Ancient Greece and Rome,” said Marianne Fourie of the International Federation for Structural Concrete. “Technological improvements and innovations over the centuries have refined its use. Structural concrete today allows engineers and architects to design and achieve striking edifices that are as robust as they can be aesthetic. Advances have also led to the more widespread use of precast concrete, which offers great benefits of cost and speed of construction.” When it comes to larger edifices, such as tall buildings and bridges, Fourie argues that nothing comes close to structural concrete for sheer strength and durability. Part of its attraction, she says, is also its versatility. “There is no reason to limit design to one material only,” said Fourie. “Assimilating other materials into concrete structure design is simple. However, structural concrete is not only used in conjunction with other materials but also incorporates them, for example, with fibre-reinforced concrete.
“Steelwork in major construction is on the rise as builders become more attuned to the advantages of using the material in easing onsite risks, speeding development for earlier returns and environmental benefits,” said Alan Marshall, communications manager at the Australian Steel Institute. The US-based Council on Tall Buildings and Urban Habitat recently reported the number of composite multi-level projects over 200 metres that typically comprise a steel frame with metal decking, rose 54 per cent worldwide in 2014. Marshall argues the case for steel under three key criteria: speed and efficiency; the reduction of on-site risks; and sustainability and waste reduction.