Article No: 53
ROWhomes on F
By: Ed Sauter
More than ever before, homeowners today seek residences that balance economy with efficiency. With utility bills and mold claims on the rise, demand has certainly increased for energy-efficient, moisture-tight homes that also offer unique architectural flair. A relative newcomer in terms of construction methods for the residential market, site cast tilt-up construction balances these demands, as showcased with the ROWhomes on F project in San Diego, Calif.
A Best in Class award winner in the 2003 Tilt-Up Achievement Awards, the 31,824-square-foot project located in a highly visible area of downtown San Diego was designed as a prototypical urban residential project that addresses both" Smart Growth's" desire for higher density (42 homes per acre) and the homeowner's desire for comfort, energy efficiency and visually unique architecture.
Conceived and designed with conservation in mind — from open space to energy — the dynamic and visually exciting urban architecture resulted from the adaptation of the "traditional" East Coast rowhome to Southern California's temperate year-round climate, according to Kevin deFreitas, project architect of deFreitas deSign.
"Traditional East Coast rowhomes are lined up, one right after another with no side yards," said deFreitas, who designed the three-story units only 16-foot-4 wide. "Because the location for these homes was in the heart of downtown San Diego, space was critical. The elimination of side yards made the rowhome model the perfect choice for this development."
While embracing the urban environment, it was essential to also provide a sense of home for the intended residences. Integrating hardy landscaping with street facing elevations that have a lot of push and pull resulted in an edifice that accentuates the sun's shadow play, making it visually interesting to passers-by, yet still offer a residential feel. Further, each rowhome has a stoop that lifts the homes 3 or 4 feet off the street --providing a buffer between the home and the street.
Noise abatement was a crucial consideration, because the project was located on urban streets with heavy traffic flow-- thus leading the design team to select tiltup concrete as the construction material of choice because of its sound attenuation properties .
"The units are a mere three inches apart and concrete does an excellent job of mitigating street and adjacent unit noise, providing an extremely quiet urban retreat despite a very close proximity," deFreitas said.
According to deFreitas, tilt-up construction was the solution for this project for a variety of reasons beyond noise abatement. First, because the 17 single-family homes are so close together that mitigating any form of water intrusion was paramount and concrete provides an excellent defense against damaging moisture-related defects. As one of the states hardest hit with mold claims, the California developers realized the importance of preventing water from invading the building envelope. Concrete proved to be the perfect solution for this challenge, because it does not support mold growth.
"Tilt-up eliminated many construction defect liabilities because it is not merely drywall over 2-by-4s — it is so durable," deFreitas said. "Beyond reducing mold problems, concrete also prevents problems over time related to dry-rot, termites and pests that can nest in traditional stick framing."
Further, the high mass qualities of concrete offered significant improvements in the energy conservation performance of the homes. In 2001, ROWhomes on F was selected for the "Energy Efficiency" residential award from the San Diego Gas & Electric in response to being 42 percent more efficient than Title-24 requirements. The project also received the tough to obtain" Energy Star" rating. Further, the concrete allows the structures to stay at a moderate temperature of 65 to 78 degrees. With operable windows, the open floor plan with no perpendicular walls allows for cross ventilation, which reduces utility costs.
Construction was a real feat considering the tight urban site with no staging area for the 217 panels, most of which were stack cast or cast off-site and measured 37 feet tall and 5 inches thick. A corner lot, the site was further plagued by the surrounding three ingress and egress streets from inbound freeways. As such, there was no option of closing streets for panel lifting, so workers were forced to work around rush hours and a steady stream of traffic.
The entire construction site was only 17,500 square feet with a 12,500-square-foot building footprint, which meant the project had to be built in phases to accommodate the lifting crane and provide some staging area. Project phasing and a tight site required that a majority of the picks of 37-foot-tall panels were "blind." Standing the panels was further complicated by the fact that there was only a 3-inch airspace between the rowhomes, thus adjacent panels. Unlike, traditional tilt jobs that have enormous floor area between panels, which makes bracing easy, the width of each rowhome was only 16-foot-4.
Because the panels were so close together, the braces criss-crossed each other, filling the entire interior cavity of each unit and preventing interior floor framing. The job superintendent, Jim Hansen of Lusardi Construction LLC, came up with the simple but ingenious solution to sleeve through both sets of panels at the airspace and brace every other unit, which allowed the alternating units to be brace free. Once the brace-free units were framed up and the structural diaphragms constructed, they could then support the adjacent panels permitting the remainder of the bracing to be taken down.
Despite the construction challenges, tilt-up allowed for a short 260-day construction schedule. But beyond speed and efficiency, aesthetics were also important. The project was designed to appeal to an urban housing niche, so the homes have an industrial/loft feel. A major selling point for the homeowners was how solid these homes were compared with traditional residential construction.
"These homes will last forever and without a lot of maintenance," deFreitas said. Features include exposed concrete interior walls, maple hardwood floors, sandblasted glass balustrades, stainless steel accents on cabinetry and stair raisers, as well as electrical cover plates. The natural concrete was enhanced with the use of saturated colors-- such as red, purple, olive and ochre.
An important attribute to maintaining the aesthetic appeal of the rowhomes was the large bay windows that have a clear aluminum anodized finish. "The mild San Diego climate allows for the use of large expanses of window, which were approximately 14 feet tall, 8 feet wide and 2 feet deep," deFreitas said.
Catering to a variety of lifestyles, ROWhomes on F was designed so that the ground floor could be used as an office or a bedroom. The second floor contains the living spaces that consists of the kitchen, dining room, living room and a powder room. Finally, the bedrooms are located on the third flood to reduce the noise from street traffic and take advantage of great city views. "This design allows for separation of non-family members who could share the space or it separates business from home," deFreitas said.
Although ROWhomes on F was deFreitas' first tilt-up project, it has been widely regarded as a success. DeFreitas credits the design-build method, as well as his firm's partnership with Lusardi Construction, for providing a cost-effective and valuable solution for this first project. By employing the design-build approach, the emphasis was placed on collaboration from the start, which allowed for early collaboration and exchange of ideas, as well as the opportunity to maximize team knowledge of systems and p r oducts. Further, early collaborative efforts maximized the strengths of the individual members for the benefit of the project and the team, as well as solidified the relationship building and trust needed to take the project to completion.
With all units sold by project completion, deFreitas has begun designing his next rowhome development using tilt-up construction.
Ed Sauter is executive director of the Tilt-Up Concrete Association, based in Mount Vernon, Iowa. TCA was founded in 1986 to improve the quality and acceptance of site-cast tilt-up construction, a construction method in which concrete wall panels are cast on-site and tilted into place. Sauter may be contacted at noSpam("esauter", "tiltup.org"); email@example.com at tiltup.org or by calling 319-895-6911.