Innovations in mass timber construction are offering new opportunities for the building industry.
The term “mass timber” is used to describe a variety of timber products that combine laminations of multiple layers to achieve greater strength than traditional dimensional lumber. Commonly used products include glue-laminated timber (glulam), cross-laminated timber (CLT), and nail-laminated timber (NLT), along with many others. These products can be used on their own or in combination with traditional construction materials, such as steel or concrete, to create the building superstructure.
Implementing Mass Timber Construction
Although it is recognized as one of the oldest building materials, wood structures are being reinvented for a variety of building types because they offer many advantages that are applicable to today and tomorrow’s needs. The use of mass timber brings exciting opportunities to explore new ways to provide a built environment that offers improved sustainability metrics, more efficient construction methods, and a multitude of occupant benefits. Wood is also a beautiful material, and mass timber products open several possibilities for architecturally expressive designs that are integrated with the building structure.
While CLT and other mass timber products are already widely used in Europe and Canada, recent expansion of mass timber construction into mid-rise, high-rise, and non-residential applications has opened the door for the wide-spread implementation of mass timber structures in the United States.
The Timber Advantage
In addition to the aesthetic and architectural design advantages that wood products offer, mass timber building systems also offer accelerated construction schedules, superior sustainability characteristics, and improved environment for occupants.
- Construction time reduced up to 25 percent compared to a steel, concrete, or light wood frame counterpart.
- Labor required for floor deck installation reduced up to 25 percent of that of a comparable concrete building.
- Roughly 1/3 the embodied energy of steel and 1/5 the embodied energy of concrete.
- Natural sequestration of carbon results in reduced carbon emissions during fabrication and installation.
- Up to 65 percent reduction in overall building weight compared to a concrete alternative.
- Reduced building weight comes with decreased foundation costs and reduced seismic loading.
- Proven fire resistance able to meet rating requirements for most building types.
- The presence of wood and other natural materials in a building reduces stress levels in building occupants.
- Improved building air quality.
Identifying Mass Timber
Some of the most common mass timber products include:
Glulam is frequently used in beam and column applications. It has a load bearing capacity similar to steel, but it is far lighter. Glulam has excellent fire resistance properties due to its mass and insulating charring characteristics.
CLT panels are formed by stacking and gluing perpendicular layers of wood, providing dimensional stability and allowing it to span two ways. CLT is typically used as floor deck, roof deck, and bearing walls.
NLT panels are most commonly used as floor and roof deck. Panels are created from dimensional lumber stacked on end and nailed together.
The Future of Mass Timber
With the increased demand for spaces that are sustainable, flexible, and efficient, the United States has quickly caught onto the mass timber model. As the technology behind mass timber continues to develop and markets realize the full economic and environmental benefits, the use of mass timber building systems is projected to blossom. As Michael Green, mass timber construction and design specialist noted at a TED Talk in 2013, “I’ve never seen anybody walk into one of my buildings and hug a steel or a concrete column, but I’ve actually seen that happen in a wood building.”
Lauren Piepho is a Structural Engineer with HGA.