Timber Tower Research Project


The goal of the Timber Tower Research Project was to develop a structural system for tall buildings that uses mass timber as the main structural material and minimizes the embodied carbon footprint of the building. The research was applied to a prototypical building based on an existing concrete benchmark for comparison. The concrete benchmark building is the Dewitt-Chestnut Apartments, a 395-foot-tall, 42-story building in Chicago designed by SOM and built in 1965.

SOM's solution to the tall wooden building problem is the Concrete Jointed Timber Frame. This system relies primarily on mass timber for the main structural elements, with supplementary reinforced concrete at the connecting joints. This system plays to the strengths of both materials. The result is an efficient structure that could compete with reinforced concrete and steel while reducing the carbon footprint by 60 percent to 75 percent.

SOM believes that the proposed system is technically feasible from the standpoint of structural engineering, architecture, interior layouts, and building services. Additional research and physical testing is necessary to verify the performance of the structural system. SOM has also developed the system with consideration to constructability, cost, and fire protection. Expert reviews and physical testing related to fire-safety are also required before this system can be fully implemented in the market. Lastly, the design community must continue to work creatively with forward-thinking municipalities, and code officials using the latest in fire engineering and performance-based design, to make timber buildings a viable alternative for more sustainable tall buildings.


This report responds to the recommendations of the initial Timber Tower Research Report, which advocates for additional research and physical testing. It consists of detailed analysis of the gravity framing components of the Concrete Jointed Timber Frame system. This was chosen as the first subject for additional research because the gravity framing components represent the majority of materials used in the structure. Therefore, these components are also the primary consideration in project cost and carbon footprint. It was also chosen because the gravity framing system involves untested connection detailing not typical of timber construction.

The purpose of the report is to provide detailed structural system information and expected behavior that could inform a physical testing program of the gravity framing system.