When you enter Skyline College’s new state-of-the-art Science Event Center in San Bruno, California, your eyes will immediately catch the sweeping views of the Pacific Ocean beyond the expansive glass walls. But just as attention grabbing is what’s underfoot, an elaborate and highly technical polished concrete floor that took a year to design and meticulous planning to install.
The 30,000-square-foot space isn’t just designed for the college, but as a showcase event location for outside companies to hold parties and symposiums. For the school’s chancellor, this included creating an eye-catching showpiece floor throughout the main conference gallery, lobby, and adjacent corridors, centered around a marble compass rose and boasting vibrant colors and sparkle. DES Architects + Engineers had worked with Floor Seal on many projects throughout the area in the past and turned to the design/build concrete firm once again for Skyline.
Perfecting the Flooring Material
Originally, the floor specification called for epoxy terrazzo. Knowing the material’s tendency to scratch and turn white, DES and Floor Seal recommended a cementitious terrazzo overlay instead. The TekFlor pour-in-place engineered cement floor topping that Floor Seal uses offers an endless array of aesthetic options with dyes and recycled glass while providing two times the compressive strength and impact resistance of standard cast-in-place concrete.
Floor Seal engaged with DES and the chancellor to select colors and aggregate for the 10,000-square-foot floor, spending more than a year experimenting and sampling. The process “allowed me to be the design/builder,” said Bonnie Boden, project executive vice president for Floor Seal. “He gave us general/key elements he wanted, but said, ‘Go for it.’”
Boden presented five different designs using a 3/8” overlayment self-leveling topping and options for mirror, gold, and glass instead of hard rock aggregate. In the end, the chancellor chose mirror aggregate and variations of gold, red, and black onyx, which he hoped could be as dark as possible.
To achieve “very dark” black, Boden partnered with Prosoco, which at the time was introducing its Integral Color for Overlays, a liquid-concentrated pigment that Prosoco says makes it easier to achieve uniformity of color versus a powder. Over the course of several months, they collaborated on testing deeper and deeper shades of black. The eventual color required five bottles (50 ounces) of black color material per bag and adjusting the ratio of water (typically the Integral Color needs just one 10-ounce bottle). Boden’s team tested in multiple samples and in the mockup itself, with both Prosoco and TekFlor signing off on the application.
Floor Seal installed TekFlor throughout much of the space, including classroom corridors, the entryway and vestibule, and into the lobby. In addition, they completed overlays on stairway. For the vertical stair elements, they pre-fabbed slabs of polished concrete at their shop, brought it to the site, and then custom cut to fit.
“It’s really an incredible sight to see when you walk down those stairs and look over this floor to the Pacific Ocean,” Boden said.
Along with the lengthy and detailed design process, Boden’s team had to plan the installation to the most minute detail, especially because the seamless look meant pouring the floor in one shot. Preparation included doing an on-site mockup to verify and work out any issues ahead of time, a strategy Boden said she highly recommends.
In working with the samples and the mockup, Boden was able to identify the ideal blend of aggregate, settling on 25% of aggregate inside the mix and 75% of it broadcasted and seeded. “You always want to be sure you’re distributing the aggregate, whether inside or outside the mix, perfectly,” Boden notes. “Otherwise you’ll have bald spots and fixes you need to go back and repair.”
It took a team of about 15 people nearly 11 hours to complete the floor with 100% broadcast, pouring the corridors first, then the center vestibule, then the main floor. They used 18,000 pounds of aggregate, custom mixed with the array of colors, and about 450 bags of TekFlor topping cement. “It was quite a bit of work, but with these type of floors you only have one shot,” Boden said. “You have to make every second count—everyone has a job to do.”
The poured floor was then polished with Floor Seal’s MirrorCrete system, a process that took about three weeks. The system uses concrete diamond tooling to deliver a specified polish, and a densification and sealing chemical process that ensure maximum longevity and stain protection.
“Working in this type of environment and working with such highly creative people like DES, there’s no words to describe how exciting and thrilling it is to be able to complete and polish,” Boden said.
The hard work paid off in rave reviews from the chancellor and multiple awards, including first place in the Decorative Concrete Council’s 2021 Project Awards for Polished Concrete Over 5,000 Square Feet.