The floating Cube

Just one year ago, on November 8, 2015, The Conco Companies completed the 12,000 cubic-yard mat pour for the new Salesforce Tower and set a record for the largest continuously pumped foundation in San Francisco’s history. Now one year later, Conco is proud to report that we successfully completed the final core wall pour and have topped off the concrete portion of the 1,070’ office high-rise to officially make it the tallest building in San Francisco.

The video above is a timelapse depiction of the last full core wall lift. The self-climbing form system used at Salesforce Tower in San Francisco is a unique construction method that has allowed for a pour cycle, also known as a “lift”, to be completed once every 3 days. This self-climbing form system is secured to the existing concrete wall below. It then raises itself in increments of 15 feet. Each section of this system, exterior and interior, move independently of the others. The less complex exterior sections take 20 minutes to complete a jump and the larger, more complex, interior system takes roughly 45 minutes to jump. When the jump is complete, the panels are aligned and secured allowing for the walls to be closed and a pour to take place. Due to a combination of characteristics from the concrete being poured and from the system itself, the cycle is able to begin again just 6-8 hours after the pour takes place.

Accomplishing this tremendous feat required exceptional organization, management and execution on the part of the entire Conco team from the very top, right down to our dedicated rebar, formwork, pump operators and placement crews. The support, partnership and collaborative effort of Clark/Hathaway Dinwiddie, a Joint Venture, the project’s general contractor, further contributed to our success. We also acknowledge the cooperation of our other trade partners, our concrete supplier CEMEX, and the project owner, Boston Properties.

To effectively and efficiently pump concrete to the upper floors of the Tower, we used the most powerful concrete stationary pumps in the industry. Furthermore, the fast-paced schedule required us to complete two floors a week, which meant a 3-day work cycle for each floor. The accelerated pace left no room for error and took the efforts of our whole team.

The building’s 14-foot 9-inch floor-to-floor heights allow for approximately 13-foot unfinished ceilings. Conco’s crew used high-strength self-consolidating concrete inside the core walls and lightweight deck-fill concrete on all floors.

Last November’s massive 12,000 cubic-yard mat pour produced a foundation that rests on 42 load-bearing elements (LBE’s) drilled 265 feet down into bedrock. The extensive site work also required more than six million pounds of reinforcing steel, mostly consisting of #18 bars (2.25 inch diameter), woven into the 14-ft. thick mat.

In addition to our extensive concrete services for the Salesforce Tower, Conco topped off the 73-story Wilshire Grand in Los Angeles earlier this year as well as placing the building’s 21,200 cubic-yard foundation in February of 2014. Conco is honored to play such a significant role in these remarkable skyscrapers that will be the tallest structures in their respective cities and the two tallest buildings west of the Mississippi River.

Conco is a leading supplier of concrete services for the Western U.S. We got our start in the Bay Area in 1959 by offering clients the best value on a wide range of concrete services and products. Since that time, we have taken a leading role as one of the top concrete contractors in the region. We have four regional offices serving California, Nevada, Washington, Oregon and Colorado.