In recent years, the rise of sustainable and innovative building materials has brought about the emergence of mass timber construction as a compelling alternative to traditional steel and concrete methods. Combining environmental consciousness, efficiency and aesthetics, mass timber is transforming the way building design and construction are approached.
What is mass timber construction?
Mass timber construction uses large, prefabricated timber panels as primary structural elements in buildings. This approach to construction leverages engineered wood products to create robust and versatile structures that can serve a variety of purposes. In contrast to light-frame wood construction, which involves numerous smaller wood members, mass timber is constructed utilizing a range of engineered wood products, frequently consisting of sizable, solid wood panels, columns, or beams. These components are fabricated off-site and can be used in load-bearing structures for walls, floors, and roofs. The collective term for these materials is ‘mass timber,’ representing a remarkable advancement in sustainable construction practices.
There are several types of mass timber, each with its unique attributes and advantages. The most common are:
• Cross Laminated Timber (CLT): CLT panels are composed of layers of laminated wood stock, with each layer placed perpendicular to the adjacent one. These panels provide exceptional strength and are commonly used for walls, floors and roofs in various building applications. Panels can be 3.5 to 12 inches thick and from four to 12 feet wide and up to 60 feet long.
• Mass Plywood Panels (MPP): These panels are formed by layering multiple sheets of one inch plywood to create panels that can be two feet thick, as wide as 12 feet and up to 48 feet long. Mass plywood panels offer greater strength and cost efficiency compared to traditional CLT panels of the same thickness.
• Dowel Laminated Timber (DLT): DLT panels consist of nominal lumber stacked on edge and fastened together with wooden dowels. This type of mass timber offers simplicity and structural integrity, typically in panels that are eight feet wide and up to 60 feet long. These panels can also have visual profiling provided by shaped 2x members adding acoustical performance.
• Nail Laminated Timber (NLT): Similar to DLT, NLT panels also use nominal lumber, but instead of dowels, adjacent boards are nailed together. NLT panels are commonly four feet wide and up to 60 feet long and are unique as they can be fabricated on-site.
Mass timber’s use and potential
Despite its numerous benefits, mass timber still represents a small portion of the total lumber used in construction in the United States. However, its popularity is growing rapidly, with its presence being felt across various market sectors including K-12 and higher education, residential, office, civic and healthcare. In 2022, there were 175 mass timber projects underway in the US, up from just 76 in 2020, a testament to the increased interest and adoption of this innovative construction method.
Benefits of mass timber construction
• Cost efficiency: Mass timber construction can significantly expedite the construction schedule due to its prefabricated nature. This results in reduced labor, equipment, and tool requirements on-site, streamlining the building process.
• Weather resilience: With proper protection and preparation, mass timber can be installed in any season. This adaptability allows construction to continue regardless of weather conditions, making it a practical choice for projects in various climates.
• Design flexibility: Mass timber offers a versatile range of engineered wood products that can accommodate diverse structural designs. While it might not be suitable for every scenario, its adaptability opens doors for unique architectural possibilities.
• Fire resistance: Despite being made of wood, mass timber projects are engineered to be fire-resistant, often meeting or exceeding the same fire ratings as steel and concrete structures. This is due to the formation of a protective char layer that shields the interior wood from damage. Mass timber elements such as glulam and CLT have been tested to withstand over three hours of fire exposure and have been tested to self-extinguish without the use of traditional fire sprinklers.
• Sustainability: One of the most compelling aspects of mass timber is its environmental sustainability. Building with wood significantly reduces a structure’s carbon footprint compared to concrete and steel. Additionally, the use of wood from sustainably managed forests enhances the local sourcing potential and minimizes transportation-related emissions.
• Aesthetics: The natural beauty of wood adds a distinctive aesthetic appeal to buildings. Mass timber’s rustic, natural, and streamlined appearance can be embraced as part of the design, eliminating the need for additional wall finishes.
• Construction efficiency: The controlled environment of a factory allows for precision cutting of openings and notches in mass timber elements. This eliminates the need for extensive on-site modifications, making the construction process quicker, safer, and more cost-effective.
Mass timber construction is undoubtedly making waves in the construction industry, offering a harmonious blend of sustainability, efficiency, and aesthetics. As its adoption continues to grow, the potential for mass timber to redefine construction practices and support a more sustainable built environment becomes increasingly apparent. With its diverse applications and myriad benefits, mass timber is not just a construction method; it’s a bold step toward a greener and more innovative future.
