Mass timber is a type of framing style that utilizes solid wood panels for wall, floor, and roof building construction and is an emerging trend that is reviving timber construction. Innovations in mass timber make it competitive with steel and concrete in larger and taller building applications such as long spans or tall walls. As the trend has grown in popularity overseas and is starting to make its way to North America, we are starting to see changes to the building codes that will allow more opportunities for mass timber, and developers and owners are also seeing further advantages mass timber has over more traditional building materials. As a firm that offers structural engineering services, we’ve done our research, and below we have provided five significant points building owners and developers should know about mass timber and how it will affect the future of the way buildings are constructed.
Mass Timber 101
Mass timber products currently consist of cross-laminated timber (CLT), nail-laminated timber (NLT), dowel-laminated timber (DLT), glue-laminated timber (GLT or glulam), structural composites (laminated veneer lumber (LVL) and laminated strand lumber (LSL). Each of these products has its advantages and the right system for each project should be selected. Mass timber is expanding beyond historic warehouses and industrial structures into office, mixed-use, public, institutional, schools, multifamily, hospitality and high-rise structures. While mass timber is not always the best option, our structural engineering team continues to study evolving trends and construction methods to provide the right solution for each project.
Code Issues and Changes
The latest edition of the International Building Code (IBC) currently limits the use of mass timber structures to six stories and 85 feet tall (based on occupancy type). These prescriptive building code limits, and a shift away from performance-based fire protection engineering, have restricted mass timber construction.
However, in January 2019, the International Code Council (ICC) approved a set of proposed changes to be incorporated in the 2021 IBC that will be in favor of mass timber and will allow these types of buildings to be up to 18 stories high and 270 feet tall. These changes have opened the door to maximizing the potential of mass timber. While the proposed code change has not yet been approved, some Authorities Having Jurisdiction (AHJs) have begun to allow buildings to be built based on the 2021 code recommendations, since they are the organization that enforces the IBC. Our engineers can work with architects and wood industry professionals to assist owners and developers in educating AHJs in hopes of pioneering mass timber projects in other areas.
The overall general perception of wood structures is that they are more likely to be a fire hazard and require additional fire protection measures that impact cost and aesthetics. This perception has created hesitation as fire hazards in tall buildings create a significant life safety concern. However, new research on mass timber is proving otherwise. The new research is supporting the heavy timber framing approach, demonstrating its inherent fire-resistant properties, and showing how fire protection can be designed using the predictability of the wood’s char rate. Like heavy timber, mass timber building components are purposefully designed to develop a char layer when exposed to fire, which acts as an insulator and protects the core of the mass timber member. Exposed mass timber can meet the code-required fire resistance rating and allow people inside of the building time to safely escape while the building maintains structural integrity.
“The number one priority for my projects and my team is life safety and the well-being of the public. Mass timber can match the fire ratings of steel and concrete construction and meet the required fire ratings in the code, thus permitting owners and developers to yield the advantages of exposed mass timber and cost efficiencies,” stated Ronald Ishmael, Associate and Structural Engineer at BHB.
Reduced Carbon Footprint
Mass timber has a smaller carbon footprint compared to other building materials such as concrete and steel, because fewer emissions are created in the harvesting process. When trees decay, they release carbon back into the environment. However, when they are harvested, the carbon is trapped inside and never released. This has a positive impact on the environment and creates less emissions as a byproduct.
Mass timber is related to another current trend known as modular construction. The panels of mass timber are prefabricated and only need to be lifted into place once delivered to the project site. This modular type of framing could lead to efficiencies in time and labor costs.
“This is appealing because mass timber projects will likely be completed faster, allowing businesses to open sooner and generate revenue,” said Ishmael. “There is also a decreased chance that there will be material defects since everything will have already been made at a facility and in a controlled environment.”
Historically used for warehouse and industrial type structures, existing mass timber buildings are now regaining popularity and being repurposed as multi-family living spaces and event venues. With a unique look and feel, these buildings have caused a spike in apartment living.
Now, mass timber is being used for new structures including office and mixed-use, public facilities, schools, and hospitality buildings. While some are 100% made from mass timber, it can also be used in combination with steel or concrete. Beyond the aesthetics, some owners are seeing benefits through occupants’ well-being (biophilic aspects) in these spaces in the form of higher returns on rents and long-term tenants.
“My interest with mass timber was sparked with the trend of adaptive re-use of historic heavy timber, as well as post and beam framed buildings,” said Ishmael. “These types of structures highlight the craftsmanship of the structural components and have an appealing aesthetic to designers.”
How to Move Forward with Mass Timber
As an owner considering mass timber, it is important to establish the best contract model to reduce cost, maximize benefits, and to take advantage of its efficiencies. Design-build, construction manager at risk (CMAR), integrated project delivery (IPD), and design assist models are proven to be the best ways to approach mass timber. At BHB, we have worked in each of these contract models with success and are invested in keeping up with the latest developments of mass timber so that we can be a strong team member and be an asset to owners, developers, and clients. Monitoring the construction of new factories and their limitations to eliminate or reduce the concerns of manufacturing capacity and availability is one way BHB provides value to our clients.
As a multi-discipline firm, we understand that MEP coordination is just as critical as the structural engineering components to achieve the aesthetic look, which is why we work seamlessly with our internal teams to allow for enhanced single-point project coordination, built-in quality assurance, and unique perspectives to effectively design and implement your mass timber project.
For more information on this upcoming trend, or to ask any questions you may have regarding mass timber, don’t hesitate to reach out to us at firstname.lastname@example.org