Architectural precast concrete provides the solution to a stand-out office building in a high-visibility location.
By Deborah R. Huso
When commercial real estate company Parker Properties decided to add a Class A* office structure to its portfolio in the planned community of Valencia Gateway in Santa Clarita, Calif., the developers knew the project was both an excellent opportunity and a challenge. “We knew there was a need for more office space in the community – Class A in particular” says Matt Jepsen, vice president of design and construction for Parker, “and the site we selected was on a cul de sac next to two hotels right on the freeway.” It made for an excellent location, but also a prominent one. There could be no skimping on the details if the building was going to attract a high-end tenant and also complement the surrounding landscape of Southern California. When construction began in 2007, building material prices were on the rise and the real estate market beginning to waver, so time was of the essence. Architectural precast concrete provided a key part of the solution.
Summit Oaks, as the building was christened (in honor of the native oaks of Southern California), was to be a 144,000-ft2 (13,380-m2) office space, designed for the ultimate in sustainability. From the start, the developers and builders were aiming for a Leadership in Energy and Environmental Design (LEED) Silver rating from the U.S. Green Building Council. Precast concrete would help fulfill the locally manufactured product points for the designation.
“The architecture we were going for was an old gentleman’s club feel,” says Jepsen. The building is trimmed in anodized bronze accents and dark glazing, all of it complementing the curtain-wall system of architectural precast that forms the structure’s earthy-looking facade.
The building’s structure makes use of recycled structural steel in a steel moment frame, which Jeff Crosier, principal with Miyamoto International, the project’s structural engineering firm, says was a critical element since Summit Oaks is located about a mile (nearly 2 km) from the San Andreas Fault. Jepsen says Parker Properties considered other options besides precast concrete for Summit Oaks’ facade, including cast-in-place concrete tilt-up panels as well as plaster construction. “Since it was a Class A, we ruled out the concrete tilt right away,” he says. As for plaster, the developers didn’t want the building to be entirely homogenous and also wanted to take advantage of the way in which they could reuse identical building members with precast concrete.
“Parker Properties really didn’t feel that plaster was Class A,” says Lon Stephenson, the project architect and director of operations for Ware Malcomb, “and stone was too expensive.”
Enhancing real estate value in a tough market
Richard Cavecche, group vice president for Snyder Langston, the project builder, whose company has built more than three dozen structures using precast concrete says, “Precast really sets this building apart. It has good aesthetics, and it’s easy to build with. It allows for ambience and detailing in the architectural design.” He feels architectural precast concrete also enhances a property’s resale value because of its durability and looks.
“Precast is a much higher-quality product, too,” adds Crosier. “It properly positioned the client in the marketplace. This is a highly visible property.” Precast concrete not only provided durability and low maintenance, but it provided Parker Properties the edge it needed to draw a high-profile tenant. “Architectural precast is a Cadillac material,” says Crosier. Precast was durable as well and, in Stephenson’s view, provided the acoustical value necessary for the building given its close proximity to the Interstate 5 freeway.
Precast concrete architectural panels were also better suited to the developer’s schedule. “We felt under the gun because of the crisis in the real estate market and the fact that we were competing with another project across the freeway,” Jepsen explains. And precast concrete also suited the local climate’s dramatic temperature variations. Santa Clarita’s temperatures can hover in the mid-30s (0 C) in winter and go as high as 95 F (35 C) in summer. The Parker Properties design team felt precast would withstand the temperature differences best and that it would also have better UV sensitivity and watertightness. Being in a highwind area, the building’s facade would need to be able to provide a barrier against water infiltration in a wind event.
Manipulating forms for faux-stone finish
The project’s biggest challenge was determining the look and texture of the building’s precast panels. “We went through a couple of samples in terms of what we were trying to capture,” Jepsen explains. Coreslab Structures, the project precaster, brought mock-ups to the site so Parker Properties and the design-build team could see how the precast’s colors melded with the surrounding environment. “We wanted a warm, rich look,” Jepsen adds, something that would mirror the look of the indigenous oaks for which the building was named.
Phil Felton, sales manager for Coreslab Structures, says showing different options for color, finish and texture on site is essential. The first level of precast incorporates a natural stone pattern, while the top four stories feature a sleek beige design. “Generally the two colors were differentiated at ground level,” explains Jon Clausen, Coreslab’s plant manager. The
lower level features a chocolate faux stone facade, and Clausen says the process for selecting it was very involved. Coreslab considered making a form liner of real stones but decided that was too costly and instead purchased a manufactured liner. But that presented a problem, because the client wanted a real stone look, and a manufactured liner shows a noticeable pattern repetition. Coreslab devised a work-around.
“We were trying to make it look like real stone,” Felton explains. “We used a purchased form liner from a local manufacturer and then tried to not make it repetitive.” To do that, they altered the form pattern elements that were used in different panels and also changed the orientation of the form. The color variation was achieved through a sandblasting process, where the precaster blasted the concrete at different angles to achieve variation in the product’s texture.
Two finishes in one panel and seamless corners
Interestingly enough, the panels that feature the faux stone are actually part of one large section that features both elements – the masonry look of the first-level facade and then the smooth beige-toned panels of the upper half of the first floor. “We achieved this by pouring the stone facade to a breakpoint, letting it get to that initial set, and then pouring the rest of the panel,” explains Clausen.
During the manufacturing process, Coreslab also mixed an integral sealer into the concrete. This represented a substantial cost savings over the traditional approach of spray-waterproofing the structure’s post-construction with an external sealer. “There was quite a bit of repetition,” Clausen explains, “but some panels were oddballs and had returns.” That meant they had to have a vertical side for turning corners. Stephenson says that it was important to everyone that the faux stone continued to look like real stonework even while turning corners on the sides of the building and at entryways. They studied a variety of colored sealants to find the best one for blending into the stone so the casual observer doesn’t notice corner seams.
The lighter-colored precast concrete panels were much easier to develop, as the building’s punched-window template held pretty much all the way around the structure. “The window modulation is very consistent,” Stephenson points out, “so there are not a lot of panel differences.”
In all, Coreslab cast 104 wall panels and 84 column covers. The largest was 20 by 13 ft. (6 x 4 m). The precast architectural panels make up Summit Oaks’ facade up to the fourth floor. The fifth floor to the roof is made up of steel aluminum cladding. Creating the architectural precast panels in the plant took about seven to eight weeks, and then the on-site installation consumed another nine to 10 weeks.
Crosier says the installation of the precast panels involved typical lateral installation. They were installed using a connection system designed in-house at Coreslab and fastened column-to-column.
Sustainability and collaboration
Upon completion of Summit Oaks in 2008, total construction costs came in at $45 million, including an adjacent poured-in-place concrete parking structure and 4.29 acres (1.74 hectares) of carefully landscaped grounds and parking area. Featuring a light-filled, two-story atrium, certified cool roofing system, onsite stormwater drainage filtration system, recycled structural steel, drought-tolerant landscape, and extensive use of locally acquired and manufactured building materials including its architectural precast panels, the building obtained LEED Silver certification shortly after project completion. It also acquired a prominent client who leased the entire building, Advanced Bionics, a manufacturer of cochlear implant systems, which has office, lab and manufacturing all under the Summit Oaks roof.
Stephenson says it’s essential to have the precaster and builder involved early in the process. “Discuss not only the aesthetic but the structural criteria,” he advises. “Make sure everyone understands attachment locations and where the joints are going to be.”
Jepsen says one thing he really appreciates about the building’s precast structure is how quiet it makes the interior spaces. “It’s so close to the freeway, but the precast concrete along with the acoustical glazing shuts out the noise from those 10 lanes of traffic,” he says.
“The project came together very quickly,” adds Jepsen. “I cannot emphasize enough the importance of those mock-ups – getting that control up on the site and considering the surroundings and the colors.”
Cavecche says collaboration is also important, because it increases project economy and reduces the likelihood of errors. He says it’s important to make sure, for example, that the steel frame can bear the load of the architectural precast concrete and then to make sure all the building’s different components (in this case, steel, glazing and precast) can be integrated for both seismic movement and aesthetics. For Summit Oaks, for example, the team needed to be sure that caulking products were compatible with glass, steel and precast.
“You have to make sure everything functions together as a unit,” Cavecche says.
Precast concrete definitely functions well in this project – especially since cost, speed of construction, sustainability and aesthetics were major factors.
*“Class A” is the top designation for the highest quality office building in a given market, reflecting high-quality design and materials, good location, state-of-the-art technology and on-site services. Class A classified buildings earn high rents and attract high-profile tenants.
Deborah Huso is a freelance writer who covers home design and restoration, sustainable building and design, and home construction.