If you’ve been following news coming out of Tindall in recent years, you will know that we offer a broad range of precast concrete systems and services to the construction industry. Calling on the technical expertise of our staff and our 60 years of experience, Tindall brings unique solutions to projects in building sectors such as industrial, residential, office, educational, correctional, data processing, and food processing. However, the one building type that seems most commonly associated with precast concrete construction is parking garages. Why is that?
Not long after the early 1950s arrival of precast, prestressed concrete in the United States, the new system made a very natural progression toward parking garages. These structures, with their continual exposure to the elements, demanded a highly durable material that could also withstand the rigors of vehicular traffic. Prior to the availability of precast, prestressed concrete systems, parking garage owners, designers, and builders were limited to the use of steel or cast-in-place (CIP) concrete for their parking projects. Both of these systems demanded significant amounts of work be carried out in the field, under whatever conditions Mother Nature had to offer at the time. These were solutions, but they left a number of boxes unchecked.
Enter precast, prestressed concrete.
The Advantages of Precast Parking Garages
Throughout the 1950s and 1960s, precast concrete manufacturing plants rapidly began appearing around the country. These facilities offered high-quality concrete products that could be produced on a daily basis under consistent manufacturing conditions. With many plants having concrete mixing capabilities on the premises, gone was the need to ship wet concrete from a ready-mix supplier to jobsite casting forms. Additionally, raw materials were stored and maintained at the factory, and quality control measures were carried out in a controlled environment by resident-trained staff. In the decades since its introduction, precast, prestressed concrete has come to be recognized as the preferred system for parking garages, with many thousands in service throughout the country.
With ongoing utilization and innovation, precast concrete parking structures have continued to expand the list of unique advantages they offer their users. Key among those is the distinct benefit it brings to the typical project delivery schedule. With the entirety of a project’s precast building frame being manufactured at an offsite factory, the project’s cast-in-place concrete foundation system can be under construction at the same time that precast members are being produced for the frame. These concurrent activities serve to compress and streamline project schedules, allowing the project to begin serving its function sooner.
The manufacturing methods that have been developed for precast, prestressed concrete also offer distinct advantages to parking garages. By making optimal use of standard members such as double tees, inverted tee beams, spandrels, and wall panels, precasters are able to refine their production methods and ensure consistent, high-quality products. Quality control measures are carried out by specialized personnel utilizing testing equipment within the facility. Many precast concrete producers achieve an even greater level of quality control by keeping their manufacturing operations under a roof or within an enclosed facility. Doing so, and in some cases introducing heat to the curing process, allows precasters to pour year-round in nearly all regions of the country.
The physical attributes of precast, prestressed concrete also lend themselves to the demands of parking structures. The often-mentioned practice of “prestressing” allows concrete beams to span greater distances with shallower depths than their non-prestressed counterparts. This enables designers of the parking garage to create large, open spaces for parking spots and drive aisles while also establishing longer lines of sight and enhanced security. Because prestressed steel reinforcement is most effective when positioned near the bottom of beams, its vulnerability to corrosion is minimized by its placement well below the weather-exposed driving surface. Early precast, prestressed concrete parking garages typically incorporated a CIP concrete topping, poured over the entire surface of the deck once the precast structure was erected. Around the beginning of the 1980s, a precast concrete parking structure system was developed that allowed the top surface of precast double tees to serve as the final driving surface, thus eliminating the need for a supplemental topping. By eliminating this field-applied layer of concrete, a highly durable precast concrete, poured with a high-strength, low water/cement ratio mix, serves as the exposed driving surface. This durable precast concrete driving surface and the elimination of major CIP concrete topping pours at jobsites have allowed the “pretopped” technique to gain prominence over the past 40+ years. As a result, it is now widely accepted as the standard approach to precast concrete parking structures throughout most of the country.
Streamlining Parking Garage Construction with Precast Concrete
As technologies advance, Tindall keeps a steady eye on materials and processes that might expand the list of advantages offered by precast, prestressed concrete. Because precast garages are comprised of connected modular members, the thermal restraint often associated with more monolithic systems can be minimized to reduce durability issues brought on by wide temperature swings. Additionally, connection details and materials are continually being enhanced to provide greater longevity and reduced maintenance. The use of stainless steel or hot dip galvanized connection hardware, ultra-dense, high-strength concrete mixes, corrosion-inhibiting admixtures, and optimized detailing of connections and reinforcement all lend themselves to providing a highly durable, long-life structure. And, given the non-combustible nature of concrete, code-prescribed fire resistance requirements are readily met without the need for special detailing or supplemental materials.
Precast concrete also offers a wide range of options for creating the desired appearance of a parking structure. With a variety of concrete colors, surface textures, integral brick, formliners, recesses, and reveals, Tindall’s design professionals can work with a project’s design team to meet the aesthetic expectations for any parking garage structure.
And finally, no discussion about precast, prestressed concrete parking structures would be complete without consideration being given to its cost versus that of other parking structure systems. As with any building system, there are multiple factors that determine how much a precast concrete garage will cost when completed. In general terms, precast concrete projects can be broken down into three major phases: fabrication, shipping, and erection. From a cost standpoint, fabrication is usually the largest of these three phases, entailing raw materials, significant factory labor, equipment, and the recurring expenses associated with operating a manufacturing facility. These types of expenses will be necessary whether members are poured on site or in a factory; however, the permanency of a factory allows the repetitive and efficient use of equipment and forms carried out by workers specialized in their use. Conversely, the likelihood of replicating this efficiency (and economy) with workers and equipment that have been mobilized to a jobsite is low.
Precision in Practice: Advancing Parking Garage Design with Tindall
By designing precast, prestressed parking garages with as many identical components as possible and using readily accessible materials, the manufacturing expense can be further optimized. This is where precasters convert “construction” into a true manufacturing environment with recurring materials, cyclic processes, and standardized members. The daily, streamlined factory production of building frame components negates the need for jobsite construction of the same members using commuting laborers and delivered raw materials. This pre-assembled, modular approach offers both economic and sustainability benefits.
The repetitive use of optimized member sizes also serves to reduce the number of pieces that must be hauled to a jobsite, picked up by a crane, and installed within the structure by an erection crew. Because the components of a precast concrete parking structure are typically large and heavy, precasters will keep a keen eye on the required shipping distance to a jobsite. Even if long hauls become cost-prohibitive for one precaster, the plenitude of precast manufacturers around the country will typically reveal another one located nearer to the jobsite. Tindall Building Systems currently boasts five locations with connecting regions, putting most projects between the Mid-Atlantic and South-Central United States in a feasible delivery range for at least one of our facilities.
When it comes time to assemble the fabricated pieces of a precast concrete parking garage, the schedule benefits become quickly evident. Utilizing a crew of only 8 to 12 workers, a crane, and assorted equipment, precast concrete erectors will install members as the precaster ships them to the jobsite. This keeps jobsite headcount and activity to a minimum, but not at the sacrifice of productivity. Of course, the time needed to erect a piece of precast concrete depends on the member type, the connections used to secure it in place, the location of the piece on the building, and the conditions under which the piece is being set. In general terms, though, an average of about a dozen pieces per day can be erected over the course of a project. In terms of constructed space, it’s not unusual for an erector to put in place 3,500 to 4,500 square feet of deck per day. Because the bays of these structures are typically erected to their full height before moving the crane and crew to the next bay, completed portions of a building can oftentimes be turned over to subsequent trades without hindering the erector’s ongoing process.
With over a thousand parking garages in its 60-year portfolio and a constant eye on the latest construction techniques and materials, the experts at each of Tindall Building Systems’ five locations can offer valuable insight during the development of any precast concrete parking garage. Reach out and see what Tindall can do for your next parking garage project.
