By Michael Russo, Contributing Editor
The use of structural concrete on the University of California, San Diego’s (UC San Diego) new Rita Atkinson Residences appears to have done wonders in complementing the design and structure of this 450-bed apartment building.
The materials chosen by the project’s design team enhanced the finishes of this $56 million building and gained the university some impressive time and cost efficiencies.
But architect Kevin Snook, AIA, LEED AP of Valerio Dewalt Train Associates (VDTA) and his partners at Webcor Builders did more than just pick the right construction materials.
“One of the most successful things about this project is that the design-build team really listened to what we were asking for in the early planning stages,” says Jana Severson, chief of staff, Housing*Dining*Hospitality at UC San Diego. “I really feel like this project was blessed from the beginning. The students love the facility, and it was wonderful to work on. I can’t say that enough.”
This doesn’t sound like the typical canned quote you’ll find in a press release, and the design team should be justifiably proud. UC San Diego leased every one of the 226 two-bedroom units to graduate students two weeks before the building even opened.
The university requires that every new campus building achieve a minimum LEED (Leadership in Energy and Environmental Design) Silver rating. UC San Diego’s criteria for the Rita Atkinson Residences were put out on the wire, and several architects and builders teamed up to compete for the project.
“One of the reasons we won the bid is we took a cost-effective approach and were determined to get some efficiencies on this project,” says Andy Schreck, vice president and regional manager for Webcor Builders in San Diego. “In order to do that, the structure needed to be cast-in-place concrete.”
In terms of square-foot costs, part of the team’s strategy was to minimize the variety of materials used. In this case, the three primary components of the building were the structural concrete frame, the stucco rain screen and windows for the exterior face of the building.
VDTA worked with Webcor to create an efficient construction time-line, maximize opportunities for increasing the number of beds, as stipulated by the university, and avoid straying above or below UC San Diego’s budget.
“Basically, with the help of Webcor, we were able to beat out the competition by providing more value and a solid design for the customer,” says Snook, who is based out of Palo Alto, Calif.
The architects used concrete for both the structural frame and the finished product, without applying other materials over the concrete in ceilings and floors. “That gave us the cost effectiveness we just couldn’t duplicate with other materials.”
It helped that one of Webcor’s core competencies is self-performed structural concrete. For this reason, the company—the eighth largest concrete contractor in the U.S.—can typically shave a couple of months or more off a standard 20-month construction schedule.
The design-build team was on track the whole time to get the project to UC San Diego one year ahead of schedule, which would have been in October of 2010.
“We hated to say to them, ‘that is fabulous, but can you do a little bit better?” says Severson. “They were actually able to finish in September, so we could catch all of the students right at move-in. The October date would have been fantastic, but we would have lost a lot of students who would already have found other housing.”
Thanks to the extra effort on the building team’s part, the university received an unanticipated revenue boost of approximately $4 million to $5 million in rentals.
“The other part of the UC San Diego criteria was to deliver a LEED Silver-rated building,” says Schreck. “So we looked at the design with the team at VDTA. Just by being a little smarter in the design and selection of materials, we were able to adjust some things and achieve a LEED Gold rating at no cost to the owner. We always like to over-deliver.”
The original master plan was to construct three individual towers for the apartment community. But VDTA took in the big picture, including the location and context of the project.
“We looked at the rest of the campus, and the concept of towers didn’t jive as well as doing something at a smaller, more human scale,” says Snook. “Instead, we created a building with multiple wings and stepped the height down to a maximum of nine stories. This helped carve away at the mass of the building and make it appear lower in scale.”
The result was one of the most active communities on the UC San Diego campus in terms of resident participation in university events.
“Hundreds of students show up,” says Severson. “This level of participation is really unheard of, particularly for graduate students who tend to work and go to bed. I think that speaks to the design of the building, and that has to do with the team listening to what our needs are.”
VDTA’s public relations representative said the firm sent a young architect to UC San Diego posing as a potential student to learn about the campus and its culture.
VDTA skillfully oriented the apartments toward one another and incorporated the leasing office, mailroom, meeting rooms and other facilities at or near the front lobby. “This helps our staff interact with residents on a daily basis and allows management to get an idea of how people are feeling about living here,” says Severson
A day at the beach
One of the things VDTA’s undercover agent discovered is that many students swim or surf in the nearby Pacific. They also tend to hang their swimsuits and wetsuits to dry indoors, which can create moisture problems in the apartments.
Because the weather in San Diego is mild throughout the year, the design team was able to forego an air conditioning system and use natural ventilation with constant airflow to battle moisture in the residences. The “trickle” vents in the operable windows and the continual draw through the roof exhaust system are most helpful in maintaining a constant airflow throughout the building.
“We looked at how to make the building efficient while aligning it with the sustainability features the University of California system likes to see,” says Snook. “We didn’t just maximize the so-called ‘graded’ sustainability features, but made decisions that made sense for the environment of the project, which led us to utilizing natural ventilation.”
The design team also reduced water usage in lavatories and used a hot water heating system instead of an electric one, which would have been more expensive in the long term.
Site issues were minimal, according to Snook, as the project was built over a parking lot. However, grading the sloped site and soil remediation work were required to increase soil densities and allow the foundation to perform as intended.
After its completion, the Rita Atkinson Residences turned out to be UC San Diego’s first LEED Gold building. The university has two more Gold-rated buildings coming on line, with a possible LEED Platinum project in the works.
When considering structural framing systems, VDTA eliminated wood construction due to height limitations and combustibility. Steel framing was an option, but it would have been more expensive and made it harder to meet the university’s budget. The architect decided on a primary structural system made of concrete with secondary steel stud infill.
VDTA worked with Webcor to come up with an attractive finish level for the concrete on the exposed ceilings and flooring, with a sealer used on the latter for ease of maintenance.
“The as-cast finish is a great, beautiful finish, which didn’t hurt the budget or require additional materials to provide a finished product,” says Snook.
This meant that Webcor did a lot of prep work on the concrete forms to ensure that VDTA would get the finish it wanted.
First, Webcor Builders and structural engineer Hope Engineering determined the concrete designs that would meet the required strengths for the building. Then they evaluated concrete forming systems that would provide efficiencies to meet the project schedule and stay within the budget, without sacrificing quality and safety.
Again, by self-performing the work, Webcor was able to control risk and gain efficiencies that would have been lost had a subcontractor been hired to perform the work.
“In terms of supply, every region is different when it comes to concrete,” says Schreck. “We had to work with some of the mix designs to get the strengths we needed. Wet concrete is a living, breathing material and coordination is important. We took extra special care when pumping and vibrating the concrete to get a consistent look throughout the building.”
Webcor subs out wood-frame construction and is more than willing to consider structural steel framing when it is cost-effective and benefits the building owner.
But, Schreck adds, “With structural concrete, you can save up to 18″ per floor on ‘skin’ costs and can also use it as a finished product for floors and ceilings.”
One thing all the participants in the Rita Atkinson project appear to agree on is the benefits of design-build construction.
“Personally, design-build is my preference because we can indicate the funding up-front and let the designer and builder come up with the best solutions,” says Severson. “We’ve used design-bid-build on campus, but with design-build you will not have to cut back. And, if you want to add to the project, you still can.”
Schreck is also a fan of “virtual” building, or building information modeling. Webcor has its own department with 3D, 4D and 5D+ capabilities that can resolve a problem “before we put a shovel into the ground,” he says.
Design-build works for VDTA as well. “We had worked with [Webcor] in the past, and we were supported by the university every step of the way,” Snook explained.
Every construction project faces some challenges, but Severson seemed hard-pressed to pinpoint any significant issues.
“The team would discuss the possibilities as questions came up,” Severson recalls. “Nothing came up as a real conflict. It was more about choices, which was wonderful.”
Weighing the options
The cost difference between steel frame and reinforced concrete, on average, is small. However, regional differences in labor and materials may favor one system over another. Costs aside, most of the designers and builders MHN spoke with generally see faster construction times with steel frame than concrete—provided that lead time for design and procurement of steel is taken into account. In the worst case fabrication and delivery of steel framing may require a six- to 10-month lead time.
“Concrete structures can go up without excessive lead times and essentially start working for you on day-one,” says one California-based engineer.
Design-wise, steel is lighter and more flexible than concrete, which is not always a good thing for sound containment, wind and seismic performance. Also, designers often need to couple the steel frame with concrete or masonry infill panels or “cores” to handle fire separation requirements at stairwells.
Concrete frames really shine in super-slender structures because they can produce a much “stiffer” system than steel within a small profile.
Over the years, new composite systems have been introduced where conventional structural steel sections are either filled or encased with concrete. Overall, these frames perform better than structural steel or concrete would by themselves. To take full advantage of these new hybrids, high performance steels, concretes, polymers and composites are becoming more popular.
“Codes produce a really heavy, inefficient building,” says Andy Ball, CEO of Webcor Builders. “And the codes become even worse the higher you get.” A performance-designed building, Ball says, uses materials more efficiently. “It costs more to plan it out, and the first few floors are more expensive, but by the end of the building, it’s cheaper.”
However not everyone is ready to race to the performance-design approach. The San Francisco Department of Building Inspection (DBI) last fall put a moratorium on what it calls “alternative” designs that don’t conform to the building code while it comes up with appropriate guidelines to handle such projects.
Going back to costs, steel construction tends to be hierarchical; the decking rests on joists, joists on beams, and beams on girders. This can make for a thicker floor, whereas concrete only requires 8” between floors to run electrical and mechanical components. On a taller building, the developer may be able to fit an additional floor into a height-limited design using concrete.
Other designers point out that while all floor systems are hierarchical, they do not normally rest upon one another and create significantly thicker floors when steel is used. Still, other architects will cite the drawbacks of long-span steel floors that tend to “bounce” more than reinforced concrete, waffle slabs and other systems with greater damping capabilities.
Steel is more economical in super-long clear span applications, which is a big selling point for commercial office developers.
Conversely, these long spans don’t work as well in residential/hotel projects because room sizes are typically far smaller. Using a tighter grid column for these projects typically make reinforced concrete more cost effective.