Case Studies
500 County Center
Mass timber meets beauty, sustainability, and budget goals for this California county
Located in the heart of Silicon Valley, the County of San Mateo needed a new headquarters to meet the needs of their growing community. The County, which oversaw a $4.9 billion budget in 2025, had three goals for the project: they wanted an iconic building, one that would demonstrate their commitment to sustainability, and it needed to be built to budget. The architects at Skidmore, Owings & Merrill (SOM) proposed a mass timber structure.
“We knew we could make the building special by virtue of the fact that it would use an innovative structural system,” said Javier Arizmendi, Design Principal and Design Lead for SOM. “We also knew mass timber would meet their sustainability values. This left budget. The contractor was already on board, which allowed us to develop real-time solutions that met the client’s financial goals.”
Upon its completion, 500 County Center was the nation’s first net-zero energy civic building constructed using mass timber, demonstrating wood’s suitability and economic viability for large-scale public projects.
Speed of construction is the biggest driver in the mass timber advantage, says Eric Long, Structural Engineering Partner at SOM. “Our experience here helped us fully realize the value of designing for construction. […] We focused on optimization—orienting the beams in one direction, reducing the number of crane picks, simplifying and having fewer connections, integrating mechanical systems with the structure, eliminating finishes … these things all added up to making the building easier and faster to build.”
Iconic Building Connects County with Community
SOM chose an H-shaped volume for the five-story structure, with ground floor public plazas that connect the city’s civic campus to the east with Redwood City’s commercial area to the west. The configuration also allowed natural ventilation and lighting to reduce thermal loads and improve occupant well-being for the County’s 600 employees. The ground level features public and civic spaces, including a large auditorium for the County’s Board of Supervisors’ chamber meetings. Upper floors contain offices, meeting rooms, and flex workspaces.
The mass timber structure combines glulam beams and columns with 5-ply CLT decking. The wood framing was sized to provide a fire-resistance rating consistent with Type IV-HT requirements; steel braced frames provide lateral support. Wood is left prominently exposed throughout, giving San Mateo County the iconic design they wanted using a sustainable material that avoided the need for extra interior finishes. The project is on track to achieve LEED Platinum certification.
Innovative Design Meets Public Budget
With this important project, SOM showed that mass timber can be a cost-competitive structural solution, even for a publicly-funded project.
SOM started by evaluating structural options, including steel, concrete, and mass timber. This step was one of many where the contractor, Truebeck Construction, added value, says Long. “They provided real-time pricing that enabled us to evaluate each option, allowing us to learn that timber was competitive in terms of initial material costs. At the same time, we ran embodied carbon calculations for all three structural types. Of course, the timber did substantially better there.”
But the number one factor in wood’s overall cost competitiveness was speed of construction, explained Long. “Once we compared the steel, concrete, and timber systems, we determined that our use of wood would save about three months in the construction schedule, which was significant.”
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