When students stroll past the three-building Centergy complex adjacent to the Georgia Tech campus in midtown Atlanta, most don't realize that the traditional red-brick cladding that adorns the three structures is an imitation. Just five-eighths of an inch thick, the bricks are merely the skin of six-inch-thick precast concrete panels that enclose the two office buildings and parking garage.
Brick-faced precast was specified over traditional brick construction for the $68 million project for its cost efficiencies, speed of construction, and simplified logistics, says Richard Peebles, a VP with Hardin Construction Co., CM/GC for the Centergy project. Designed by Atlanta-based architect Smallwood, Reynolds, Stewart, Stewart & Associates, the complex consists of a six-story, 218,000-sf, single-tenant office building, a 14-story, 500,000-sf speculative office tower, and an eight-story parking garage for 1,175 cars.
"With traditional brick, it probably would have taken four to five months to enclose the buildings," says Peebles. Using brick-faced precast shaved more than a month off the exterior enclosure schedule, he says.
Precast also priced about $1 cheaper than brick construction ($26/sf vs. $27-28/sf) and eliminated the need for scaffolding, which can be "extremely expensive" for buildings the size of Centergy, says Peebles. "Plus, it makes for a much simpler envelope because you don't have to worry about whether the flashing is installed correctly, or if the mortar's falling into the cavity, or the waterproofing of the sheathing. There's not as much that can go wrong."
About 300 brick-faced precast concrete panels — some as long as 40 feet and weighing 15 tons — form the shell of the complex. They were shipped from Gate Precast Co.'s Ashland City, Tenn., fabrication plant to the job site, where a huge tower crane swung them into place and erectors welded them to connection plates embedded into the cast-in-place concrete structure.
About 300 brick-faced precast concrete panels form the shell of the three-building Centergy complex in Atlanta.
Peebles is quick to add that cost estimates on other recent projects have come out in favor of traditional brick and concrete block construction. He says the price of brick-faced precast — which runs $1-2 more per sf than standard precast concrete — generally depends on three factors: the size of the pieces (the bigger, the better); the number of pieces (the fewer, the better); and the degree of articulation and detail in the brick skin (the simpler, the better). Peebles says cement costs have to be figured in, too. For instance, smaller projects that require a higher level of detail may lend themselves better to traditional brick construction.
Nor does precast brick offer as much design flexibility as conventional brick. With regular brick, he says, you can have rows that protrude and others that are recessed, which you can't do with precast. Also, precast has joints, so the design team has to pay more attention to where the joints are located, says Peebles.
While it represents a small fraction of the overall brick and concrete block market, brick-faced precast concrete, first developed in the 1960s, has seen moderate growth over the last decade stemming from more competitive pricing and greater demand for fast construction methods.
Gate Precast has offered brick-clad precast for more than 20 years, but only recently has it sold the product on a regular basis. "In the past, we'd be lucky to get a project every four or five years," says Dean Gwin, president of sales and marketing for Gate's six architectural precast concrete manufacturing facilities. "Now we keep at least one project in production at all times."
Gwin says the biggest growth has come in the K-12 schools market, which demands fast construction and the traditional look of brick. To cater to this sector, Gate offers a load-bearing precast brick inlay system that acts as a complete wall system — including insulation, interior wall finishing, and even electrical conduit.
"This one panel takes the place of block, brick, vapor barrier, metal studs, insulation, conduit, and sheetrock," says Gwin. "It's installed much like tilt-up concrete — braced, then the steel structure is built inside."
A precast fabricator lays 5/8-inch-thick brick tiles into a mold. Form liner keeps the bricks in place and spaced apart to replicate the look of traditional mortar joints.
The precast wall consists of a 2-inch-thick layer of extruded polystyrene and polyisocyanurate insulation sandwiched between 3- and 5-inch-thick concrete panels; these are tied together with nonconductive, chemically resistant fiber composite connectors. Panels sizes are as large as 30 feet in height and 15 feet wide (supporting a two-story structure). They can be installed at the rate of about 2,500-3,500 sf a day, compared to 500-700 sf a day for typical brick and block systems, says Gwin.