Non-Traditional Structural Materials Are Gaining Favor Among Forward-Thinking BuildersConsider the Alternatives

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So why hasn't steel taken off among home builders? Simply, the system requires framers to carry an entirely different set of tools. Hammers become screwguns, while utility knives and chalk lines are replaced in a framer's toolbelt with snips, vise grips, and felt markers. Usually, instead of a wood framer switching to steel (or being skilled enough to do both), builders switch to steel framers-if they can find them.

That fact, in turn, severely limits a builder's ability to use the material as a structural system in all but a few markets. "I've built all-steel houses, and both then and now there's no one doing it [as a specialty trade]," says Orlando custom builder Williams. For the small-scale, second-floor shell he built out of steel in 2006, Williams had to import a crew from another market and supplement it with a local commercial drywall crew to finish the job.

"The lack of lead framers who know steel framing is our biggest hindrance in single-family," admits SFA's Williams. Price is another, specifically as it relates to the installed cost of a steel frame by inexperienced crews or those in short supply able to leverage premium wages. "Worst case, steel is about 81 cents per square foot more than a wood-framed house," he says.

To combat those issues, the industry is evolving into panelization from the precut or uncut "sticks" that suppliers traditionally provide to a jobsite. An example: recently unveiled insulated steel-framed panels from Accelerated Building Technologies, a joint venture of Dietrich Metal Framing and NOVA Chemicals.

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.

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.

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.

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, a custom home builder in Orlando, Fla.