Tilt-up Main Street
Site-cast tilt-up concrete construction is more likely to be associated with big-box suburban warehouse stores than with boutiques on Main Street. A row of 60 storefronts that adorn the Mount Pleasant (S.C.) Towne Center, however, showcase the versatility of the concrete technology. Each of the shops in the new retail development was constructed with tilt-up, yet each has a unique architectural appearance, creating the feel of a traditional small-town business district instead of a modern shopping mall. While the stores look as if they are made of brick, plaster and other traditional materials, the entire 425,000-sq.-ft. project was constructed with tilt-up concrete.
Located across the harbor from Charleston, Mount Pleasant is a rural fishing village and summer retreat. When its population tripled in the 1980s, the town formed a commercial design-review board to preserve some of the vernacular architectural heritage of the Carolina coastal region. The board turned down bids from several developers to build conventional shopping centers and mandated that commercial projects had to reflect the historic character of the village.
To meet this mandate, Konover Property Trust, a Cary, N.C.-based retail developer, retained Richard L. Bowen & Associates of Cleveland as project architect and VanderPloeg & Associates, Boca Raton, Fla., as design architect. The team developed a scheme that maintained Mount Pleasant's street grid, allowing the warp and woof of the streets to weave the new development into the existing neighborhood's fabric. The plan also called for on-street parking and pedestrian amenities to fill the streets with shoppers.
Stores were clustered into city-block-sized structures. To make it look as if the buildings were constructed one at a time, the designers varied the massing, fenestration, roof lines, ornamentation, signage and finishes of each storefront to reflect the changing building styles popular throughout the region's history. Where veneer façades were used, the designers detailed them so that windows would be set back from the wall plane and appear to have actual sills and lintels. Deep recesses and projections and corbels were also employed to give the walls visual depth.
Complicating the design's historicism was the need to satisfy the demands of contemporary retail stores. For example, the pedestrian scale façades had to be mated to large clear span interiors.
Initially, tilt-up was specified only for part of the project. As the team gained confidence with it, however, it realized that the system would save time and costs in other areas. Tilt-up was substituted for drywall and masonry demising walls for the steel structures proposed for four buildings on the site and for the precast concrete proposed for a 16-screen movie theater. Eventually, tilt-up was used for all 17 buildings on the site and resulted in estimated cost savings of nearly half a million dollars.
Fast-track construction began without complete designs or tenant commitments. As with most retail projects, several tenants required space changes once construction was under way. For instance, Old Navy required a major expansion and a redesigned façade. To solve the problem, panels which had already been installed at the front of the store were moved to the rear expansion, enabling the modifications to be made without waste.
All concrete panels were produced on the job site, using the building's floor slabs as casting beds. Because the concrete work was performed while the panels were in a horizontal position, costs for scaffolding and formwork -and labor - were minimized.
To create the variety of finishes required, panels were painted, textured with form liners, clad with ceramic tile and coated with synthetic stuccos and exterior insulation and finish systems (EIFS). The thickness and profile of the EIFS insulation could be varied to create cornices and other ornamental features. Two techniques for installing thin brick veneers were used to replicate the look of traditional masonry buildings. In some instances, the nominal 1/2-in.-thick bricks were set like ceramic tile, adhered to walls with a thin-set mortar. In other cases, the brick was laid on the casting bed before concrete was poured. Plastic spacers were used to maintain the alignment of the thin bricks during the pour and to create lines between bricks.
According to Glenn Doncaster, president of Citadel Contractors Inc. of Raleigh, N.C., the project tilt-up contractor, the special shapes and ornamental features of the panels required more elaborate formwork than typical tilt-up buildings. Engineering the panels to resist hurricane winds - despite large open areas for store display windows - was another challenge.
Still, according to Dale Scott, vice president of general contractor Keene Construction Co., Maitland, Fla., the tilt-up system enabled the team to get buildings enclosed quickly, providing a head-start on interiors work.
Construction was completed 2½ months ahead of schedule, and the center has enjoyed high tenant occupancy rates. The acceptance of Mount Pleasant Towne Center by the citizens of Mount Pleasant, however, has been the most important attribute of the project. As design architect Derek VanderPloeg describes, 'Even when the stores are closed, people come here to stroll, walk their dogs and just hang out. The community has begun to think of this project as the new heart of their town.'