A Construction Primer: Precast Vs. Site-Cast
Commercial construction is an intense and complicated topic. When the subject is building envelopes, the discussion can be as vast as it is deep with opinions. Obviously, there’s more than one way to build a building, but two styles often confused for one another are structural precast concrete panels and site-cast panels.
First, some quick definitions. “Tilt-up” describes an installation technique where a crane tilts finished panels into place. Although this process is used for both precast and site-cast panels, it’s important to understand the defining characteristics of the two styles. With precast construction, large concrete panels are cast in a climate-controlled manufacturing facility, transported to the jobsite via flat bed trucks, and then set in place. With site-cast construction, large panels are cast at the jobsite, usually on what will become the floor slab. To the untrained eye, the end product can be very similar, and in some cases, almost indistinguishable. The differences, however, are significant.
For starters, consider the number of aesthetic options and finishes that are available with precast. Precast offers building professionals and owners a robust palette of finish options, including aggregates, formliner imprints, thin brick, and three variations of sandblast. Because precast panels are manufactured in a controlled environment, a higher level of quality and consistency can be obtained. Curing rates, for instance, can vary greatly on a jobsite, but a climate-controlled environment maintains an ideal temperature.
Physical and structural differences exist as well. Take height, for instance. Fabcon Precast is now producing panels that are more than 73 feet tall. With site-cast panels, anything over 40 feet becomes tricky to engineer and increasingly cost-prohibitive. Thermal performance is another critical difference. Precast panels have an integrated insulation component with the ability to deliver R-values up to R-28.2. Adding insulation to a site-cast envelope is an added step in the process and requires a whole new set of subcontractors.
Additional advantages to the precast process begin early in the construction cycle. While the site-cast crew is waiting for the jobsite preparation to be completed, a precaster like Fabcon can begin producing panels and preparing them for delivery. Factors like weather and excavating crew availability can affect when the jobsite will be ready… and it’s never sooner than anticipated.
Both systems are relatively fast when it comes to setting panels, but while a precast crew of six workers can enclose 100,000 feet in less than 2 weeks, a site-cast crew of 20 (or more) can only erect them as fast as they can cast and cure the panels. The site-cast panels are manufactured in the open air and exposed to the violent swings of Mother Nature's fickle mood. Weather, once again, has the ability to push the schedule, the curing process and ultimately the final cost and quality of your building envelope. Even once site-cast crews have left the site, their legacy might linger; pouring the panels on the floor slab may have damaged it to an extent that serious repair or complete replacement is required.
With a site-cast project, you can count on more guys and more equipment being on the job site longer. That not only monopolizes access to the site, it exposes you and your organization to added risk and liability. To be fair, site-cast isn’t the worst way to build a building — it just has its limitations. For a more in-depth look at the advantages of structural precast, visit FABCONVERSUS.COM.
For 47 years Fabcon Precast has been a leading force in structural precast concrete construction. Superb thermal qualities, speedy construction and design flexibility make Fabcon Precast an ideal partner for the most aggressive timetables and the most modest of budgets. For more information, contact Fabcon Precast at 800-727-4444 or visit FabconPrecast.com.
Jim Houtman is Vice President, Sales & Marketing at Fabcon Precast. Jim oversees Fabcon Precast’s sales team and helps lead continued industry thought leadership efforts. Since 1981, Jim has worked to educate building professionals and shape perceptions surrounding structural precast construction.