For the last 200 years, wood has been a consistent player among building construction materials. Historically, large members of old growth timber have been used as structural components, only to be replaced in the 19th and 20th centuries by structural steel and concrete as large, old-growth forests became more limited for sourcing raw building materials. Further research and development led architects and builders in Europe to reevaluate the merits of wood construction, particularly as an environmentally friendly option, with new construction innovations allowing mass timber to reenter the construction world as premanufactured wood products. These new innovations married the best of old-growth strength with the adaptability of smaller wood fragments.
Mass timber construction continued to proliferate throughout Europe during the 1990s and 2000s, followed by a surge of mass timber projects in Canada and the Pacific Northwest. Mass timber construction in the United States has begun to gain momentum, but still focuses primarily on commercial and public buildings with large, sweeping spaces.
As wildfires ravage the West Coast and hurricanes pummel the South, the environmental impact of our built environment and the resulting climate change demands new solutions for construction innovation. Tracking the life-cycle environmental impact of a building requires consideration of all stages of construction: raw materials, manufacturing, transportation, construction, post-occupancy, building maintenance, and end-of-life. Building materials and construction contributes roughly 11 percent of total global greenhouse gas emissions (United Nations Environment Global Status Report 2017). Within that 11 percent, structural systems typically comprise as much as 80 percent of the embodied carbon in a building.
Design Concept
The Timber Tower concept uses a 10-foot-by-13-foot-6-inch column grid with a five-ply CLT panel. Elimination of beams on the residential levels reduces the floor-to-floor height, allowing for unobstructed views and simplified MEP distribution. The columns sit adjacent to the demising walls, providing a clear air gap between units for a true acoustical separation. Floor-ceiling assembly options include either a dropped ceiling or an acoustic barrier between the CLT panel and the finished floor system. At 12-stories, the Timber Tower building proposes Type IV-B construction, allowing 20 to 40 percent exposure of the CLT structure. This exposed wood finish would be primarily concentrated in the unit living spaces, supporting the biophilic design benefits of natural materials in unit interiors.
While CLT construction can easily sit over a traditionally constructed concrete parking structure, CLT transfer beams can spread the weight of the building above to accommodate a single story of parking at the lowest level. To maximize parking at the ground floor, mechanical parking lifts stack cars up to three cars high over grade with an additional stack in a subterranean pit. Varying dimensions of the mechanically stacked parking accommodate both standard and compact-sized parking spaces.
