Mass timber products are growing in popularity as a substitute for steel and concrete, reducing embodied carbon in the built environment. This trend has raised questions about the sustainability of the U.S. timber supply. Our research addresses concerns that rising demand for mass timber products may result in unsustainable levels of harvesting in coniferous forests in the United States. Using U.S. Department of Agriculture U.S. Forest Service Forest Inventory and Analysis (FIA) data, incremental U.S. softwood (coniferous) timber harvests were projected to supply a high-volume estimate of mass timber and dimensional lumber consumption in 2035. Growth in reserve forests and riparian zones was excluded, and low confidence intervals were used for timber growth estimates, compared with high confidence intervals for harvest and consumption estimates. Results were considered for the U.S. in total and by three geographic regions (North, South, and West). In total, forest inventory growth in America exceeds timber harvests including incremental mass timber volumes. Even the most optimistic projections of mass timber growth will not exceed the lowest expected annual increases in the nation’s harvestable coniferous timber inventory.
Throughout the last two decades the timber building sector has experienced a steady growth in multi-storey construction. Although there has been a growing number of research focused on trends, benefits, and disadvantages in timber construction from various technical perspectives, so far there is no extensive literature on the trajectory of emerging architectural typologies. This paper presents an examination of architectural variety and spatial possibilities in current serial and modular multi-storey timber construction. It aims to draw a parallel between architectural characteristics and their relation to structural systems in timber. The research draws from a collection of 350 contemporary multi-storey timber building projects between 2000 and 2021. It consists of 300 built projects, 12 projects currently in construction, and 38 design proposals. The survey consists of quantitative and qualitative project data, as well as classification of the structural system, material, program, massing, and spatial organization of the projects. It then compares the different structural and design aspects to achieve a comprehensive overview of possibilities in timber construction. The outcome is an identification of the range of morphologies and a better understanding of the design space in current serial and modular multi-storey mass timber construction.
Numerous studies have shown that the geometry of micro-joints significantly affects the strength of the so joined timber element. The bending strength increases by creating a larger bonding area by increasing the length of the wedge joint. Although this type of joint has been successfully used for many years, it can still be troublesome to make. For these reasons, the present study investigated an easy-to-fabricate wedge joint, which we folded during the beams’ formation and glued with the same adhesive as the individual lamellas. Although the research has not fully answered all the questions relevant to both scientific and technological curiosity, it indicates the great potential of this solution. Following the principle adopted in the ongoing wood optimisation work, we concluded that the beams of the target cross-section should be produced, and it should only be possible to cut them to a certain length. In this approach, we only removed defects at critical points for the beam structure and, in this way, up to 30% of the timber processed could be saved or better utilised.
Wood waste has the potential to be used in making a variety of goods, including engineered wood products, energy generation (heat and electricity), mulching, and animal bedding. These inexpensive and underutilized feedstocks have the potential to increase the added value of wood wastes. This paper aims to review the different possibilities on wood waste utilization and their prospects in Nepal. This information helps to find the proper way for future development of wood waste to deliver the best outcomes for the environment and economy. The review is based on an in-depth examination of credible literature and official statistical data. The study showed Nepal has not utilized wood waste except for firewood and a few engineered wood products. The problem with wood waste is the lack of adaptation of advanced technologies and the lack of institutions concerned with the benefits of utilization of those waste. This review concludes that wood waste can be a potential source for the production of different materials but the government should develop effective waste management rules to maximize the value of wood waste resources.
Engineered wood products, such as glulam beams, attract much attention from the building industry in recent years. Therefore, there is a constant necessity to seek new models of structural beams, which assume the use of outsized sawn wood pieces as an alternative for the standard construction timber. Three variants of glulam beams, composed of the main yield and side boards arranged in various structures, were proposed. Moreover, the usefulness of wedge-jointed, small-sized timber pieces was also investigated. The manufactured beams were tested, in terms of their mechanical properties, such as bending strength, elastic energy, modulus of elasticity, and resilience. The outcomes have shown that the beams manufactured using wedge-bonded timber of lower grade do not deviate considerably from beams produced from homogeneous lamellas. Furthermore, the results of modulus of elasticity, in the case of the three-layered beams composed of both small-sized non-homogenous main yield and side boards, exceeded the requirements from EN 14080. It allowed us to classify the obtained materials as GL 32c, which is the highest grade specified within the standard.
A new connection concept for joining cross-laminated timber (CLT) plates in their secondary direction is presented. The connection consists of two laminated veneer lumber (LVL) gusset plates with finger-joint-like profiles milled on one side which are glued onto the outermost layers of the CLT. It is demonstrated that the joint represents a stiff moment resistant connection, enabling the activation of the normally underutilized biaxiality of CLT plates and expanding the design freedom of architects and engineers. The concept was analyzed by means of analytical and finite element (FE) models for two geometry alternatives, differing in either a 2D or 3D tapered finger profile. The 3D tapered finger profile produced a stress reduction of around 5% in the region of stress concentration and a more even shear stress distribution on the bonded surface. Thereafter, four specimens were manufactured – two of each geometry alternative – and then tested in four- and three-point bending setups in order to assess the behavior at pure bending as well as at combined moment and shear loading, respectively. At pure bending, the studied connection delivered bending capacities of 100% of the characteristic value of the unjointed CLT material. For the case of moment and shear loading, the global capacity was determined by a bending failure in the CLT region subjected to maximum moment, while the joints remained unbroken. Measured deformations and strains during the tests validated the FE model, which can be used to further develop the connection concept, which allows for a full activation of the biaxial behavior of large-span CLT floors.
Mass timber continues to be a hot topic of discussion within the development industry in British Columbia. The International Building Code now allows for mass timber to be used for buildings up to 18 storeys. The change allows developers to consider it for residential multi-family projects and prompts one big question: “What will it cost to build my high-rise project with mass timber in our market?”
The team that developed this report represents an independent team of architects, structural engineers, quantity surveyors, and a general contractor. Consultants from fire, building code, and acoustic industries also provided expertise to the study. In late Fall 2020, we formed an industry group in Vancouver to answer this question with an exclusive focus on the local market. We identified a need for a significant shift in the local industry’s building philosophy when using mass timber as a structural material.
Our goal was to assess the viability of mass timber for this product type in British Columbia by comparing the cost, construction methods, and schedules of a typical concrete high-rise in Vancouver to those for the same building using mass timber as the principal structural material. To undertake the study, the group created virtual models of the base building and conceptual models for side-by-side detailed comparisons.
While gaining in popularity, building a high-rise with engineered mass timber remains an unconventional method in British Columbia. To support the industry, we wanted to fill in gaps in data to better understand and help solve the challenges of working with new materials and techniques needed for mass timber construction at scale.
This study presents what we learned about cost, schedule, and code implications as well as methodology efficiencies. It must be noted that the study took place over a period in Q2 and Q3 of 2021 when lumber and steel prices – two of the principal materials – experienced high volatility in supply and record increases in price.
Since every building project and market is unique, the report makes no claims concerning specific cost or time frame. Rather, it identifies what to consider in creating a reliable framework for optimizing costs and schedules while meeting code requirements when building residential high-rise mass timber buildings.
The use of cross-laminated lumber (CLT) for building construction has gained interest in the United States (US) and Canada. Although anecdotal market size claims exist, few quantitative studies have estimated the potential market size or discussed the impact of CLT on lumber supply. This paper presents a method to quantify CLT markets and lumber supplies based on data for the Northwest US. The western US was chosen for its early adoption of CLT combined with a long history of commercial timber construction. Structural designs of archetype buildings were combined with projected multifamily residential and commercial building construction to estimate the demand for CLT. These figures were reduced to account for assumptions that address market penetration and population density. In the case study for the Northwest, the total potential market is less than the existing CLT production in western North America. Thus, the demand region was expanded to include the US and Canada west of the Rocky Mountains, resulting in an estimated demand of 800,000 m3/yr by 2030. A regional lumber supply study suggests that the lumber supply will support the existing CLT industry, which utilizes approximately 2% of the selected lumber classifications, with an unknown impact on lumber cost and production.
The development of this primer commenced shortly after the 2018 launch of the Mass Timber Institute (MTI) centered at the University of Toronto. Funding for this publication was generously provided by the Ontario Ministry of Natural Resources and Forestry. Although numerous jurisdictions have established design guides for tall mass timber buildings, architects and engineers often do not have access to the specialized building science knowledge required to deliver well performing mass timber buildings. MTI worked collaboratively with industry, design professionals, academia, researchers and code experts to develop the scope and content of this mass timber building science primer. Although provincially funded, the broader Canadian context underlying this publication was viewed as the most appropriate means of advancing Ontario’s nascent mass timber building industry. This publication also extends beyond Canada and is based on universally applicable principles of building science and how these principles may be used anywhere in all aspects of mass timber building technology. Specifically, these guidelines were developed to guide stakeholders in selecting and implementing appropriate building science practices and protocols to ensure the acceptable life cycle performance of mass timber buildings. It is essential that each representative stakeholder, developer/owner, architect/engineer, supplier, constructor, wood erector, building official, insurer, and facility manager, understand these principles and how to apply them during the design, procurement, construction and in-service phases before embarking on a mass timber building project.
When mass timber building technology has enjoyed the same degree of penetration as steel and concrete, this primer will be long outdated and its constituent concepts will have been baked into the training and education of design professionals and all those who fabricate, construct, maintain and manage mass timber buildings.
One of the most important reasons this publication was developed was to identify gaps in building science knowledge related to mass timber buildings and hopefully to address these gaps with appropriate research, development and demonstration programs. The mass timber building industry in Canada is still a collection of seedlings that continue to grow and as such they deserve the stewardship of the best available building science knowledge to sustain them until such time as they become a forest that can fend for itself.
In a context of environmental concern and limited urban land, the construction industry faces the challenge of providing solutions for the increasing urban population both efficiently and sustainably. Numerous innovations on engineered wood products for multistorey buildings arise as one of the most promising solutions. In this context, various policies have facilitated the development of Tall Wood Buildings (TWBs). Yet, few publications analyse these policies and their influence on specific projects. This research aims to examine the impact of Policy Instruments (PIs) on individual TWBs qualitatively. Data collection is based on documentary review and semi-structured interviews with policymakers and professionals involved in 37 projects across eight countries. This study reveals that numerous TWBs have been facilitated by policies, acting through diverse PIs applied combined or in isolation. Notably, while Regulatory Instruments allowed TWBs in the first place, Research and Development Tools supported their development and approval process. Often, Research and Development Tools subsidised demonstration projects through Economic Instruments, after competitions or applications (Voluntary Policy Tools). Moreover, many Information Tools (e.g. campaigns, technical assessments) complemented other PIs. Remarkably, while some TWBs have become legal and technological precedents, technical information resulting from their development has influenced proposed changes in building codes.
