Precast Concrete Panels
Precast concrete is a panelized system for poured concrete in which wall and floor sections are molded and cured in a factory setting, shipped to the jobsite, and craned into place to create the structural shell and bearing walls. Increasingly, precast panels incorporate an integral layer of rigid foam insulation to increase the thermal mass properties of the system.
Top: Crane costs can be prohibitive for a small-volume or custom builder, but better amortized across a larger project being built within a single phase. Bottom: Correct openings are critical in precast, requiring extensive engineering and planning before the panels are cast, as changes are costly to make.
Credit: Photos: www.constructionprogress.com
Panelization in general is already an accepted and increasingly common method of home building, especially to combat shortages in skilled labor via faster on-site assembly. Precast concrete panels have hung onto the coattails of the trend toward component wood framing and, to a lesser extent, SIPs. As of last year, precast reached an estimated 2.7% share of above-grade walls in single-family construction, equaling about 41,000 new homes, up from a zero share just a decade earlier by NAHB's count. Its use as a below-grade foundation system, meanwhile, is estimated to be about 8% of the residential market, with some geographic markets (those near manufacturing facilities) measuring significantly higher.
Like steel framing, precast cut its teeth in commercial, quickly becoming a faster way to build repetitive building sections in multi-story, multi-unit projects. The system translates across the International Building Code, enabling its use as a foundation and above-grade wall system in a residential setting.
As with any of the structural alternatives, precast concrete panels present some attractive benefits. Akin to their faster on-site assembly (by some industry estimates, they can save up to three weeks compared to wood framing), precast panels are an all-weather system. They provide an efficient thermal mass, increasingly supplemented by integral insulation, that significantly reduces–if not eliminates–the transfer of air and moisture through the structure.
That benefit not only reduces energy use and costs for homeowners, but often enables smaller and more efficient (and less expensive) HVAC equipment specifications as well. The system also delivers superior sound abatement and resistance to a variety of natural forces, such as high winds and fire.
All those benefits, however, have yet to produce a sweet spot in single-family housing, a segment that precast may never crack on a large scale. Custom builders like the system's performance aspects, but can't afford the one-time cost premiums for engineering, shipping, and crane-assisted assembly. Large-volume production builders, meanwhile, are generally too price-sensitive to consider anything out of their comfort zone of wood-based systems; on a per-foot materials basis only, precast might cost at least 20% more. "If your details are very complex or you're just building one home, the project is not a good candidate for precast," says Bock. "If you're only concerned about the bottom line, this is not the system for you."
Another hurdle to acceptance for any builder is the system's requirement for exceptionally detailed planning for all openings and mechanical runs; simply, once the panels are cast, those placements are set, literally, in stone. "There's no room for error. You have to be dead-on," says Mike Williams. It's a process he says requires weeks of planning, engineering, and confirming specs–time that most builders are loath to spend when other structural systems are so easy to manipulate in the field to fix mistakes. "But, once the panels are in place, it takes all the guesswork and time out of where to locate those things."
Low- and mid-rise multifamily housing, attached townhomes, and small-scale subdivisions of similarly styled single-family homes are likely to be where precast finds its niche. "If you are building 10 homes on the same block, it makes more sense," says Bock, a scenario that amortizes the cost of the panels and crane rental across multiple units while significantly shortening cycle time. "There's an economy of scale that can be achieved."
Distribution is arguably the biggest impediment to precast's achieving widespread popularity. More so than any other alternative system discussed in this series, the system's proliferation is tied to the proximity of the jobsite to a manufacturing plant, typically within a 300-mile radius. "We franchise our system to local manufacturers with exclusive distribution to control the brand against other building products," says Aaron Schoenberger, director of marketing for Superior Walls, a precast panel manufacturer that targets only foundation applications.
The company's current network of 21 franchised plants supplies builders east of a line extending from Minneapolis to Orlando, a geographic region in which basements are common. A new plant is an investment of up to $3 million, says Schoenberger.
Like SIPs, a direct relationship between a builder and the system's manufacturer is almost requisite given the planning that needs to take place before the panels are cast, a process that can take months instead of the minutes a framer might spend grabbing a few 2x4s on the way to the jobsite.
For dealers, even supporting the system with ancillary products is a sketchy proposition. Manufacturers typically supply a turnkey system, including anchors, industrial sealants, and connectors, limiting a dealer's role. Even sales efforts are usually self-contained at the manufacturer or franchisee, with a few independent reps scattered about, exclusively selling one system.
Any increasing use of precast concrete panels, as with any alternative structural system for housing it seems, will continue to be pulled along by builders rather than pushed through distribution. "The success of this system will be driven by innovative builders willing to pay for it and sell its benefits [to homeowners]," says Bock, a statement that could be applied to precast, structural steel framing, SIPs, and ICFs, at least in the near future.
–Rich Binsacca is a contributing editor for ProSales.