The Battle Between Wood and Concrete
New construction techniques promise changes to the apartment development industry, but materials interests should not be afraid.
When it comes to building mid-rise multifamily residential buildings, there’s a new kid in town. Wood frame construction is already shaking up the development industry, prompting people behind the traditional ways of doing things to warn against embracing the new construction technique just yet. Is wood the new super-material that will take the purpose-built rental apartment industry into the future? Or are we unwise to throw the old ways out with the bathwater?
A Concrete Foundation
The traditional method of building multifamily residential buildings is with concrete. Concrete was invented in 1824 as Portland cement, and the material was used in building construction as early as 1854. As the material advanced, its flexibility, durability and strength led to the first concrete high-rise building being built in Cincinnati, Ohio, in 1904. As skyscrapers started rising on the skylines of cities through the twentieth century, concrete as well as steel led the upward charge.
As a building material, wood was around centuries before concrete. It was easy to obtain, versatile, and lightweight, an ideal building material for single-family homes and other small buildings. As urban development from the 1950s onward polarized between low density suburban housing subdivisions and high-rise apartment towers, wood and concrete each staked their territory. The line between the two wasn’t blurred until the early part of the 21st century.
The Rise of Mid-Rise Wood
Around the year 2000, new construction techniques and new lumber products started to make wood a useful construction material in larger buildings. At the same time, cities across North America moved away from the modern suburban-style development towards a more diversified urban fabric. City planners wanted to encourage pedestrian friendly streets with increased densities, and while high rises offered higher densities, extremely tall buildings might not be appropriate for a particular urban environment, or the core of a small town. Instead, to increase densities along suburban arterial roads, many cities looked to mid-rise residential and commercial buildings to provide higher densities with pedestrian and transit-friendly environments.
Here, wood had a decided advantage in the new build form. Concrete and steel were appropriate for high-rise construction but were expensive. Building mid-rise buildings out of concrete and steel were less cost-effective. Wood was lighter, which made it cheaper to transport and build with. Mid-rise buildings built out of wood could be more profitable for developers than ones built out of concrete and steel.
Wood Transforms the Industry
In 2009, British Columbia changed its building codes to allow wood frame construction for buildings up to six storeys tall. Since then, more than 300 mid-rise wood-framed buildings have been built or are under construction in the province. Quebec, Ontario, and Alberta also changed their building regulations to allow for six-storey wood around 2013 and, in 2015, the National Building Code of Canada permitted wood-frame construction for six-storey residential and commercial buildings.
The United States has followed this trend as well. Recently, the developer of North Tract Lofts in Arlington, Virginia, changed its building plans from concrete to wood frame construction. The developer said the move could shave 40% from the total construction cost of the project. Another example is the WREN multi-family project in the South Park district of Los Angeles. The $144 million development features seven-storey buildings made out of wood that conform to California’s strict earthquake-resistant construction regulations.
Concrete and Steel Push Back
The push for wood has been enthusiastically supported by lumber and forestry interests across North America. The concrete and steel industries, fearing the loss of market share, have fired back, questioning the wisdom of changing the building codes, and questioning the safety and environmental sensitivity of wood as a construction material for mid-rise buildings. Those concerns were amplified when a wood-frame five-storey, 241-unit building under construction in downtown Raleigh caught fire and burnt to the ground.
The American National Ready Mixed Concrete Association created a coalition called Build with Strength, with a mandate “to educate the building and design communities and policymakers on the advantages of ready mixed concrete and encourage its use as the building material of choice for low-to-mid-rise structures.” Spokesman Kevin Lawlor said, “What a lot of folks in the NRMCA saw was wood products and combustible materials becoming a product of choice in the low-to-mid-rise residential construction market, and knowing that they had a safer, more durable product, wanted to do something about promoting the product in the space so that we could convince more people to build with concrete for all the benefits that it brings to the table.”
Perceptions to Overcome
As a new construction technique, wood has to overcome a number of preconceptions, and prove itself on a number of issues. A study conducted by GLOBE Advisors for the Concrete Council of Canada noted that insurance premiums for wood-framed buildings were six times higher than comparable concrete buildings. The study cited four major concerns to justify the higher rates: greater fire peril, significantly higher moisture risk resulting in potential mold and mildew contamination, the ability of wood frame buildings to handle severe weather including storms brought about by climate change, and “difficulty in obtaining insurance for wood frame structures”.
That last concern is clearly a self-fulfilling prophecy, since citing the difficulty of wood frame buildings in obtaining insurance itself increases the difficulty of obtaining insurance. However, Len Garis, the chief of the Surrey Fire Department in British Columbia downplayed the safety concerns, saying, “The safety level of buildings, once completed and equipped with the required protection systems under the building code, would be equivalent to that of any similar building constructed with other materials.” The building that burnt down in Raleigh, it was noted, did so when it was under construction and at a phase that most buildings, regardless of their construction materials, are at their most vulnerable.
How Green is Wood?
Wood also has some perception issues to overcome when it comes to its environmental footprint, given the controversy the forestry industry sometimes faces. However, proponents of wood note that the North American forestry industry is increasingly following sustainable practises when harvesting wood, and wood’s environmental impact becomes more favourable when considering the environmental impact of steel and concrete.
Concrete, for instance, is typically made up of 60-75% aggregate, and 15-20% water. Aggregate has to be removed from the ground in quarries and doesn’t grow back. The manufacturing process requires energy and produces pollution. Steel is made from iron that has to be mined and then smelted in blast furnaces that reach over 1,600 ‘C, again requiring considerable fuel and adding to steel’s carbon footprint. By comparison, wood absorbs carbon dioxide before it is harvested, removing it from the atmosphere. Unlike aggregate or iron, or the fuel used to produce them, wood is a renewable resource. Many North American sawmills are even using woody biomass rather than fossil fuels to fuel their operations.
A Place for Every Material
If wood frame buildings are as safe as buildings made of concrete and steel, then it’s only a matter of time before developers come to understand the benefits as well as the risks associated with the new mid-rise construction method. As the insurance companies get more data on wood frame buildings operating safely, they will lower their risk assessments, and insurance premiums will drop.
It is unfortunate seeing interest groups of various construction materials square off in this fashion. Wood has a big part to play in the changing landscape of urban form, and it offers a construction technique that will save developers money and will be easier on the environment. Yes, some questions remain, but the research on wood as a mid-rise construction material is continuing. In July, officials at LP Building Products and the Network for Earthquake Engineering and Simulation organized a shake test on a seven-storey tall, 23-unit condominium tower made from LP’s wooden I-Joists and its SolidStart Laminated Veneer Lumber. Weighing more than a million pounds, this shake test will be the world’s largest, and officials from the U.S. and Canadian governments will be in attendance, watching with interest.
Concrete and steel interests should not be afraid about losing market share to wood. There will continue to be a need for high-rise construction, and technological advances in concrete construction, including 3D printing of concrete forms, will increase the role that concrete has to play at all levels in the development industry. The key is to innovate, rather than stifle innovation.
Wood, concrete, and steel will continue to be vital components in the development industry to come, but developers now have more and better tools with which to build their buildings. As it gets cheaper to build, more and better buildings will be built, which will benefit all.