The concrete solution you choose will depend on design, schedule, and priorities. Here are advantages of each approach.
Parking garages may look alike, but as you know, the structure’s construction engineering can vary dramatically. At the beginning of the design phase, and sometimes even closer to the inception of the project, I’m often asked about the differences between parking garage concrete solutions and why they matter. It’s a great question, and one I love to answer.
There are two primary ways to construct a garage: with precast or cast-in-place concrete. Here’s what makes each approach unique and advantageous — and project examples that help explain the differences.
Precast, Pre-Stressed Concrete
What is is:
Precast, pre-stressed concrete are formed offsite and delivered during construction. Precast, pre-stressed concrete works best for projects that require an expedited construction schedule on tight sites that do not allow for stressing of post-tension tendons. Tendons are stressed alongside the building; if there are adjacent buildings or the structure under construction is underground, the tendons must be stressed before getting onsite.
• Faster construction schedule. The pieces are cast in a plant and shipped to the site for erection; form decisions have to be made early.
• Construction is not as affected by the weather, because the pieces are cast indoors rather than fighting the elements outside.
• Potential for a lower initial construction cost, because early design decisions limit any formwork needed in the field.
• Architectural design can be incorporated into the exterior panels.
We used this material on the $2.5 million parking garage at The Landings in Cincinnati, Ohio. The 57,000 sq ft, 2-story structure sits on a small site beside an $18 million, 184,700 sq ft office building. During our team’s discussions with the owner, we found that schedule and budget were key. At the time, precast, pre-stressed concrete had a significantly lower construction cost versus cast-in-place, post-tensioned concrete and the owner was happy with the faster construction completion.
Cast-in-Place, Post-Tensioned Concrete
What it is:
Cast-in-place concrete is poured into place onsite. Slabs and beams are poured together so fewer joints are produced reducing lifecycle costs. Joints require maintenance such as sealant that must be replaced regularly. Cast-in-place, post-tensioned concrete works best for projects where long-term durability and lifecycle costs are the priorities.
• Typically offers a more open layout, because the moment frames produced by the beams and columns cast together can resist the load without reliance on additional walls.
• Better distribution of light inside the parking structure. The beams are spaced every 20’-24’ rather than tee stems every 5’-6’ in a precast, pre-stressed concrete garage.
• Easier to customize the shape of the framing members and the overall building footprint thanks to the ability to alter the formwork onsite.
Schaefer used this material for a garage on an expanding Fortune 25 company’s Ohio headquarters. This 260,000 sq ft, cast-in-place parking structure consists of five levels and holds 800 vehicles. Added complexities included two pedestrian bridges branching off of the garage’s third level to adjacent buildings.
In discussions with the owner, our team understood that structure durability and minimal maintenance were the most important factors; all other attributes, including project schedule, fell below these. Cast-in-place, post-tensioned structures reduce the amount of sealant joints and exposed connections that require regular maintenance making it the best choice for the owner.
At Schaefer, we believe there is no one-size-fits-all solution for parking structure construction. We start the design process for every project at the same point – the beginning. It’s the best way to understand the unique needs of the final product and the best possible construction techniques required.
Nathan Walsman, one of Schaefer’s leading parking engineers, designed two award-winning parking structures. Parker Flats won the Juror’s Special Mention at the CORA Residential Design Awards and The Congress of Residential Architecture, and AIA Cincinnati recognized the project as “excellence in residential design.” Belle of Baton Rouge Parking Structure was honored by South Central Magazine with their Award of Excellence, Private Building. To see more parking examples, visit our Projects Page.