Cross-Laminated Timber Changing Views on Multifamily Construction
- Feb 17, 2017
Some of multifamily housing’s boldest designs were born from dreaming big. But what if we dreamed big about building those designs? Some of the most futuristic building materials available today are the manifest of big dreams, and in a single product – Cross Laminated Timber – could change the way we design and build multifamily structures in the future.
Cross Laminated Timber (CLT) is an engineered wood building system that has widespread adoption in European countries. This engineered wood building system is made from several layers of dimensional lumber, stacked crosswise and glued together. This provides dimensional stability, strength and rigidity, making the product a viable alternative to concrete, masonry and steel in many applications. With careful planning and engineering considerations, the service life of a CLT building can last as long as buildings constructed from other materials like concrete or steel. Even better, the manufacture of CLT components for a building dramatically reduces the amount of time and size of crew needed to assemble a CLT structure.
Here are the Top 10 CLT qualities that could influence your decision:
With proper design and maintenance, wood structures can provide long and useful service lives equivalent to other building materials. The key is careful planning and understanding of environmental loads and other external factors likely to impact a building over its lifetime.
Strength and Stability
Cross lamination provides for superior dimensional stability and offers significant shear strength performance at a very unique weight to strength ratio compared to other common structural materials. CLT panels outperform anything currently available in the USA.
CLT panels can create an effective lateral load resisting system. Researchers have conducted extensive seismic testing on CLT and found they perform exceptionally well with no residual deformation, particularly in multi-story applications.
Because the mass of the wall contributes to acoustic performance, CLT building systems provide superior noise control for both airborne and impact sound transmission.
CLT panels are better insulators, requiring little or no insulation. Since CLT panels can be manufactured using CNC equipment to precise tolerances, the tighter-fitting panel joints results in better energy efficiency for the structure. The solid panels also mean nearly zero air infiltration into the building envelope. Interior temperatures of a finished CLT structure can be maintained with just one-third the normally required heating or cooling energy.
A thick cross-section provides valuable and superior fire resistance for a CLT panel. Their mass means they char slowly, slowing and eventually stopping combustion. With fewer concealed spaces, fire cannot spread undetected. Compared to concrete and steel structures in a catastrophic fire event, CLT structures suffer less degradation.
Moisture Management & Vapor Diffusion
Wood is naturally hygroscopic, serving as a moisture management system within a building envelope. Ideally manufactured at 12 percent moisture content, wood’s ability to absorb and emit moisture can naturally stabilize an indoor environment. CLT buildings “breathe,” minimizing the risk for mold growth and maximizing the comfort of its occupants.
Wood is the only major building material that grows naturally and is renewable. Studies consistently show that wood outperforms steel and concrete in terms of embodied energy, air pollution and water pollution. CLT also has a lighter carbon footprint as wood products continue to store carbon absorbed by the trees while growing, and engineered wood manufacturing requires significantly less energy to produce than concrete and steel.
Healthy Indoor Environment
The only constituents of a CLT building system are wood and a non-toxic/non-VOC adhesive. CLT building materials do not introduce any toxins into the indoor environment providing clean indoor air quality. CLT wall systems are naturally breathable. Integrated with appropriate mechanical systems, this creates a healthy indoor environment that maximizes occupant comfort and health.
Life Cycle Analysis
The longevity of CLT components ensures that the future value of any structure remains high. CLT buildings are easily altered and remodeled and are also fully recyclable once they reach the end of their useful life.
The versatility of CLT means it could be used throughout a building, or to construct a single building feature, like it was for a multilevel building currently under construction in Whitefish, MT that specified a CLT elevator shaft. If the construction team was using poured concrete for the shaft, they would have had to budget for a process involving 8-12 people, several inspections, added equipment to form and cure the shafts—and then a month to allow for the shafts to cure in place. Compare that to a CLT shaft, preassembled in a warehouse with much more controllable weather conditions, which can be assembled on site with just three people and a crane operator. The savings compared to concrete are in the neighborhood of 70 to 75 percent.
Not only structurally viable, CLT panels also contribute a raw visual beauty unlike any other construction material. While it may be comprised of building products we relegate to the past, their design, strength, and sustainability mark CLT as the construction material for multifamily housing’s future.
Casey Malmquist, president and general manager of SmartLam, has served in this position since SmartLam’s inception in January of 2012, and has led the SmartLam team from the ground level to becoming a globally recognized producer of Cross-Laminated Timber products. Malmquist has over 30 years’ experience owning and operating a successful construction and development company.