• Scalable performance. Precast construction allows for scalable performance. New energy codes and ASHRAE requirements demand varying thicknesses of continuous insulation. Precast concrete wall panels can be easily tailored to meet these requirements while avoiding many of the detailing difficulties of cavity and composite wall construction.

• Low life-cycle costs. A precast façade can be designed to match the intended life of a building with minimal maintenance, providing substantial long-term savings. Precast concrete panels present a durable, aesthetically pleasing exterior surface that is virtually airtight and watertight and does not require painting. Precast envelope systems also help minimize the total number of joints relative to other envelope systems. This helps the building remain in first class condition with minimal maintenance, ensuring its desirability to future tenants or owners.

• Risk reduction. Several attributes of precast concrete allow for reduced construction risk, reduced professional liability, lower construction complexity, and greater profitability. As a single unit, precast systems provide a single source capability for supplying the entire exterior wall system. When loadbearing precast structural floors, along with panels, are specified, the entire building structure and superstructure can be provided through one certified and reliable precast producer. The precaster is responsible for meeting design specifications, as well as for all manufacturing and constructability issues, minimizing the number of subcontractors and attendant coordination of trades. The precaster's staff of plant engineers is available to assist the design team on the project from the concrete mixture design to the optimum component size for production, shipping, and erecting purposes (see sidebar). In addition, material optimization and reduced need for detailing as described above, all work to enable the builder to do more with less, conserving resources, both material and human, and reducing construction spends.

Designers can exert more control over the final appearance of the structures because they can view finish and range samples as well as mockup panels prior to full-scale production. The architect and owner can visit the precast plant to monitor progress, ensuring that no surprises arise at the site. Plant production's high quality-control standards result in tighter tolerances, too, all of which leads to a smoother, faster fit during erection that speeds construction and minimizes the need for on-site adjustments.

Precast concrete is different from site produced concrete because it is made in a factory by highly trained and experienced personnel who apply stringent quality-control measures. In the factory environment, precasters are able to achieve consistency in temperature and moisture, and meet low water-cementitious ratios that are essentially not possible in field cast-in-place concrete. Precast concrete typically possesses strengths of 5,000 psi to 7,000 psi or more, with densities that minimize moisture and bulk water permeability.

Precasters as Design-Build Partners

Precast concrete components can provide a number of advantages to a project. These advantages can be best optimized if the design considers the material from the conceptual stages. Using precast concrete components to construct a design that was originally planned as a cast-in-place project, for instance, may require changes and adaptations to the precast concrete pieces to create the monolithic style the cast-in-place design provided. Those changes may not work to precast concrete’s efficiencies, creating an inefficient design that is more cumbersome and difficult to erect than one in which precast concrete was the material of choice from the start. At best, precasters should have the opportunity to value-engineer an existing design to make full use of the precast concrete’s efficiencies, including higher strength mixes conducive to creating long spans and eliminating columns. Precasters can consult on a project during the early design phase without having to be given a commitment to producing the components they help conceptualize. They can advise in such areas as mix durability and strength; panelization (sizes and layout); bay sizes; repetition possibilities for reducing form materials and cost; efficient shipping sizes and configuration; seismic needs for joints; finish options; connection issues such as prewelding; scheduling, including production timing and sequencing of cranes; and cost data, including helping to create a guaranteed maximum price. After the project is designed with the precast concrete components outlined, the job can be put out to bid among a variety of precasters, ensuring that low costs are maintained while still achieving maximum value from precast concrete’s capabilities.