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San Mateo County Office Building #3

Apr 5, 2022 Chelsea Drenick, SE

San Mateo County Office Building #3

Owner: San Mateo County
Architect & Engineer: Skidmore, Owings & Merrill LLP  
General Contractor: Truebeck  
Timber Installer: Western Wood Structures 
CLT Supplier: SmartLam

The new 208,000-square-foot County Office Building 3 (COB 3) is under construction on the lot across from the Hall of Justice in downtown Redwood City, CA. Slated for completion in late 2023, the building will have five stories of office and meeting space that will accommodate ~600 San Mateo County employees. The building will include a cross-laminated timber (CLT) floor structure with supporting glulam columns and beams to help meet the County’s green building standards, including net-zero energy and LEED Platinum certification. 

On February 25, 2022, Chelsea Drenick interviewed Laird Bennion, a consultant with the San Mateo County Project Development Unit. Laird is project manager on the County’s two mass timber projects—County Office Building #3 (COB3), and the San Mateo County Wellness Center, which is in permitting in South San Francisco. The interview has been condensed and edited for clarity. 

What were some of the key motivators that led the San Mateo County to use mass timber on this project? 

Mass timber is an incredibly promising material–it’s beautiful, strong, and surprisingly lightweight. On COB 3, we have seen significant cost reductions for the foundations with mass timber. Construction schedule savings were another benefit we saw with mass timber.  

We wanted a project that would stand the test of time; the County wants a building that will be flexible and continue to serve their needs throughout many different programs and uses. With the exposed structure and flexibility of the space, we really think this is possible. We also designed COB3 to a higher standard so it can last 100 or more years—which means that’s how long the wood will be storing carbon, or longer if it’s reclaimed and used somewhere else. So, there’s a lot to like.  

San Mateo County Office Building #3 / Skidmore, Owings & Merrill LLP
Can you talk a bit about what role sustainability played in the choice of material? 

Sustainability was front and center in our material selection. The building is designed to be net-zero and will be LEED Platinum certified. When we considered steel and concrete as the building materials, net-zero was a goal, but with mass timber it was attainable. We need to be operational for a year before we know if we meet the net-zero goal; so, we will be tracking our operational carbon emissions closely. 

At what stage in design was mass timber selected for this project? 

During schematic design, steel, concrete and mass timber options were explored. Mass timber, including CLT floor and roof panels and glulam post-and-beam, was chosen at the end of schematics as the best approach.  

What were the biggest hurdles the team faced on this project using mass timber? 

Mass timber is an innovative new material, so it is seen as a risk. San Mateo County took a chance with this, but they believed it was the right choice from the beginning. Don Horsley, current President of the Board of Supervisors, was excited about mass timber and wanted to use it as a building material because it made so much sense for this project. I think more governmental entities should lead by example. The County Project Development Unit – Adam Ely, Sam Lin, and County Manager Mike Callagy have been great to work with and so supportive of the project.  

Along the way, during design and permitting, there was pushback from some entities who expected this building to be constructed using steel. They also assumed a timber building is more likely to catch fire. It has been a process of education, discussing the inherent fire resistance of mass timber, and explaining the safety of the material.  

The County has been wonderful to work with and supportive of this innovation, and it’s really paid off with a beautiful and functional building. Mass timber has the potential to change architecture the way concrete and steel did in the 19th and 20th centuries.  

San Mateo County Office Building #3
The project is currently under construction. Have other benefits emerged that you didn’t anticipate? 

We knew a lot of the benefits of mass timber from the beginning, which is why we chose it.  It makes so much sense for a class A office building. We knew about the speed of construction, increased construction site safety, and the beauty of the finished product. Another benefit is significant noise reduction on site. When we constructed a parking garage nearby, we received a number of noise complaints. With this project, no noise complaints.  

What we didn’t expect was people’s emotional response. We see a lot of people taking photos of the building, and they ask about the project. People feel good watching this building go up. I was anticipating a positive reaction, but did not expect how overwhelmingly positive it has been. 

I was giving a tour the other day and one of the guests told me that it was the ‘best smelling construction site’ they’d ever been on. Quite a compliment!  

Can you tell me more about the second project you’re working on, the San Mateo County Wellness Center?  

We’re really excited about the other project as well. San Mateo has a number of healthcare facilities around the county that are being consolidated into one building. The new building will be three stories, with two stories of offices over one story of clinical space. This consolidation will help the County save costs while allowing it to offer a higher level of service by having all the healthcare services under one roof.  

Any advice for building owners interested in using mass timber on a project for the first time? 

We thought we were taking more of a risk when we opted for CLT over steel.  When you look at the benefits of the material versus the limitations, the decision makes itself.  

Connect with the San Mateo County Office Building 3 team on the WoodWorks Innovation Network (WIN).