Marissa Kasdan – Timber for Tomorrow: Mass Timber Construction for MF
Colorado Real Estate Journal
September 21, 2021
It’s official, the building code has changed. The International Building Code’s recent expansion of Type IV (heavy timber) construction to include buildings of up to 18 stories has made building higher with wood possible. Utilizing heavy timber as a primary structural system for new multifamily developments expands opportunities but also raises questions. At a time when cities across the nation struggle to meet housing needs, the expansion of mass timber construction supports increased residential development and addresses some of the challenges facing high-density multifamily construction projects. As an alternative to concrete or steel structural systems, mass timber provides another design solution with distinct material properties.
KTGY’s R+D concept Timber Tower includes a sweeping ground-floor lobby space featuring a natural design aesthetic.
Lower cost. Wood construction generally indicates a lower-cost design solution when compared with concrete or steel. Even with the recent price increase in lumber, the cost of wood is still consistently lower than other high-rise options. After reaching a record high in May, the lumber industry is already seeing prices begin to drop and the market expects prices to continue decreasing as recent disruptions in the lumber supply chain begin to stabilize.
Better for the environment. The environmental benefits of selecting mass timber over concrete or steel are clear. As a renewable resource, wood offers a solution associated with inherently lower embodied carbon. Additionally, the use of cross-laminated timber or other wood-based engineered products minimizes construction waste and provides exceptional design flexibility.
To maximize parking within a mass timber structure, mechanically stacked parking fills a single-level garage at the ground floor of Timber Tower.
The increasing severity of wildfires in the West and hurricanes in the South have highlighted the incipient environmental crisis that demands new solutions for construction innovation to reduce the construction industry’s effect on climate change. Building materials and construction contribute roughly 11% of total global greenhouse gas emissions (United Nations Environment Global Status Report 2017). Within that 11%, structural systems typically comprise as much as 80% of the embodied carbon in a building. Concrete, the most widely used construction material globally, includes both raw materials and manufacturing practices that produce a concerning amount of embodied carbon. Steel as a structural system also contributes significant embodied carbon to the environment, however, the amount varies widely depending on the manufacturing process and share of recycled content.
In response to the recent addition of new variations to Type IV construction in the International Building Code, KTGY’s R+D concept, Timber Tower, proposes a 12-story residential design solution using cross-laminated timber as the primary structural material.
The opposition. But not everyone shares this excitement about the expansion of mass timber construction. Proposals linked to the concrete lobby, such as a suggested expansion of Los Angeles’ Fire District 1, aim to limit the use of wood-framed construction for larger developments. Preying on an understandable fear of fire danger, newly proposed restrictions ignore the many provisions written into the International Building Code to thoroughly address fire safety for mass timber buildings. Sprinkler systems, wood wrapped with fire-resistant materials, and char zones provide the fire safety precautions necessary for high-rise multifamily housing developments.
Timber Tower represents a possible solution for how mass timber ,onstruction can minimize construction cost and reduce the environmental impact of high-rise residential development.
Looking at the opportunities. To better understand the challenges and opportunities ahead for this new type of residential development, KTGY’s R+D Studio studied many variations and applications of mass timber construction for high-density multifamily design and developed Timber Tower, a conceptual design prototype using cross-laminated timber for a 12-story residential building. To fully capitalize on the use of CLT, the Timber Tower concept proposes a single story of CLT-framed parking, with mechanically stacked parking to maximize the provided parking spaces. A 10-by-13-foot-6-inch column grid with a five-ply CLT panel and the elimination of beams on the residential levels reduces the floor-to-floor height, allowing for unobstructed views and simplified mechanical, electrical and plumbing distribution. Columns sit adjacent to the demising walls, providing a continuous air gap between units for enhanced acoustical separation. Floor-ceiling assembly options include either a dropped ceiling or an acoustic barrier between the CLT panels and the finished floor system. At 12 stories, the Timber Tower building proposes Type IV-B construction, allowing portions of the wood finish in the interior spaces to remain exposed for a unique and natural design aesthetic.
Our Timber Tower concept design represents only one of countless potential solutions for replacing concrete or steel structural systems with mass timber, but a study of the opportunities and limitations clearly shows how residential construction can more sensitively respond to the growing challenges of climate change. Mass timber construction minimizes embodied carbon while achieving the necessary structural and fire-resistance requirements for high-rise buildings. New construction innovations and code modifications related to mass timber create green design opportunities that will benefit the future of sustainable communities and our environment.