Tall Wooden Buildings

Multi-story buildings have traditionally been the preserve of the modern building materials concrete and steel. Sky scrapers developed from the ability to erect a steel framework from which curtain walls are suspended, rather than load-bearing walls of conventional construction modern building materials. New engineered wooden building materials and recognition of the environmental benefits of building with wood are changing the mind-set and increasingly wood is being designed into more, and taller, buildings.

I typed "tallest wooden building" into Google in an effort to locate information on what was described as the "World's tallest apartment building under construction in Melbourne's Docklands" as reported in the Australian Forest Growers journal, winter 2012 edition.

As with most things Google, I got 58 million hits. Good to see there is plenty of information on this topic! The one that caught my attention was a website about the unveiling of a proposed 30-storey wooden building for Vancouver along with an instruction manual for building wooden sky scrapers.

Canada is leading much of this research as it strives to reassert its forestry industry as a strong and viable sector amidst slumping domestic and US demand (depressed housing market), the loss of forests from the mountain pine beetle kill and competition from substitutes (such as concrete, steel, aluminium and plastic composites).

It produced a comprehensive and well-researched document called THE CASE FOR Tall Wood BUILDINGS – How Mass Timber offers a Safe, Economical, and Environmentally Friendly Alternative for Tall Building Structures funded by the Canadian Wood Council. This 237-page document provides a compelling case for tall wooden buildings, including design and costing details and it debunks many of the common myths surrounding building multi-storey buildings with wood. Notable positive attributes of building with wood include -

  • Fire resistance – large wooden posts and beams char on the exterior when exposed to fire and offer superior fire resistance to steel.
  • The Mass Timber building systems allow construction up to 30-stories and perhaps higher.
  • Total building costs are competitive with steel and concrete structures.
  • Foundation cost can be reduced, especially in areas of poor soils, due to the wooden structures being lighter than concrete and steel.
  • Good seismic performance of wood structures.

Wood is one of the most sustainable building materials available in the world. Wooden buildings have high environmental credentials such as high thermal efficiency, low embedded energy and a low carbon footprint. A typical North American timber-frame home sequesters some 28 tonnes of CO2; equivalent to seven years of driving a medium-sized car, or 12,500 litres of petrol.

The Food and Agriculture Organisation of the United Nations (FAO) states that one of the most effective means of combating climate change is to have a thriving and responsibly managed forestry and forest products industry. The demand for valuable forest products enables countries to avoid deforestation and degradation, afforest depleted lands and sustainably manage forests they already have. The adoption of the principle of recognising carbon in wood products by the UNFCC will monetise this value.

Mass Timber building systems provide the building blocks for tall buildings – there are three primary Mass Timber wood products –

  • Cross Laminated Timber (CLT) made from layers of solid wood set at 90 degree orientations
  • Laminated Strand Lumber (LSL) made from a matrix of thin wood chips
  • Laminated Veneer Lumber (LVL) made from thin veneers of wood similar to plywood but much larger in scale.

With new design of Mass Timber structures tall wooden buildings can out-compete concrete and steel on the basis of cost, performance, environmental attributes and aesthetics.

Canada should be applauded for its significant investment in rejuvenating its forest products industry. Fortunately much of its work will provide positive spinoffs for New Zealand. It should also be an inspiration for the New Zealand forestry and wood products industry to more actively promote itself and develop new product opportunities in selected markets. The Christchurch rebuild is an obvious place to focus (as has been occurring) but we can do much better and should extend our aspirations more broadly into both NZ and selected export markets.