Whole Foods is known for its sustainable foods and loyal customer base. When the company was ready to build a new retail center in Lexington, Ky., the owner wanted the new building to have a rustic feel, as if it had always been part of the community.
“It is a look that would have been difficult to achieve using any material other than precast concrete,” says Steven Schweitzer vice president of operations for Gate Precast Company. The building site had an existing shell with "leftover armatures” from the building’s prior life. Gate was brought on-board to construct a building around it that looked like it “had some years on it and a story to tell,” he says.
The biggest challenge was delivering a structure with a worn appearance while delivering top-of-the-line energy conservation through insulation and new construction. The transitions of the panels and their materials had to coincide with the color of concrete that was selected and had to become seamless around the building. “Through the addition of new exterior skin materials and canopies, the structure was retrofitted for its new life as a grocery store,” Schweitzer says.
Barn wood and distressed brick
The use of formliners in the precasting process helped realize two of the building’s exterior material expressions—distressed, aged brick and salvaged barn wood.
Gate used a combination of three finishes to achieve the desired brick look. Two were used in the panels, and the third was applied after the panels were erected. Using pictures that the owner provided of the desired finish, Gate’s team tried several types of tumbled brick and multiple techniques in the forming process to find a solution that delivered the look and feel without exceeding the limited budget.
They ultimately settled on two concrete mixes, with the two brick colors randomly assigned in a 60/40 split. To achieve the limewash effect, they allowed the concrete slurry to come into the mold on the corners and edges and randomly cover parts of the brick, breaking up the traditional brick wall mold.
The exposed surfaces on everything but the brick were lightly sandblasted. The brick face was “as is” coming out of the mold.
“We were all doubting the unfinished mortar look because it seemed so sloppy,” Schweitzer says. “But once we saw the panels in place, it pulled the architect’s vision together and made the appearance so successful.”
To complement the brick, a hemlock wood liner was selected; this choice was a tribute to the wood-sided tobacco barns that were on the site prior to the project’s development, Schweitzer says. The panels were colored with gray pigment and finished with a light acid to emulate the rustic timber. Wood siding from the original barns was salvaged during site demolition and used elsewhere in the development as accents. “The implication is that the same wood was used to form the precast concrete panels, giving the exterior a similar texture, grain, and pattern,” he says.
To meet the energy code requirements, each panel is insulated with 2½ in. of polyisocyanurate insulation in the core. “This allowed a quick one-step solution for the shell and a delivery of a total insulated wall system, which left flexibility for the tenant to figure out what they wanted to do inside,” Schweitzer says.
To accommodate the weight of the 12 ft by 30 ft insulated panels, the erection crew initially braced the panels from the interior until load could be transitioned to the steel roof.
Once the panels were cast, erection took place over winter, which can be especially tricky in Kentucky, where the ground may be frozen one day and thawed the next. The variable conditions “turned the construction site into a mud pit,” Schweitzer says. Despite the weather, the erection was completed in 45 days, and everyone was pleased with the result.