By Robert Whitmore, courtesy of PCI IW

Efficient and flexible, podium style design works for developers and contractors

The challenge for developers in today’s building environment is to make the best use of limited space while providing amenities that will attract tenants and buyers. The solution is often a tried-and-true design mode that marries a sturdy concrete base with a light wood-framed tower. Podium-style construction, in vogue since the 1960s, remains popular because of its inherent advantages in maximum use of space, structural efficiency and design flexibility.

A common podium configuration consists of one or more levels of a plank-beam-column parking structure below ground with the upper deck, often hollowcore, providing both fire separation and structural transfer. In addition to the parking structure below, podium configurations often include an additional story of precast at the ground level for mixed use space, with four or five stories of wood-framed construction above.

The International Building Code considers podium-style construction as two separate structures – one on top of the other. The horizontal separation between the lower concrete podium and the wood structure above enables podiums to meet IBC fire-resistance ratings (IBC Section 510.2) more easily.

For the contractor, podium building design solves a host of issues, according to Aaron Gundlach, senior project manager for Krupp General Contractors, based in Madison, WI.

“It gives us a solid surface to start our wall construction,” Gundlach said. “It cleans up a lot of load transfer details for the walls. And it gives us a nice clean separation for a UL fire-rated assembly. With metal decks and wood trusses, we get into way more complex systems to meet the necessary UL assemblies that separate the garage from the floors above.”

Krupp General Contractors frequently works with Mid-States Concrete on podium projects in Wisconsin. Based in South Beloit, IL, Mid-States also erects most of the beam-column-hollowcore structures it produces.

Brian Blum, Mid-States Concrete senior project manager, spent 15 years installing podiums before moving into project management 10 years ago, “So I’ve been doing podiums every week for 25 years,” he said. While the podium style has been common during that time, developers are looking at real estate costs, the availability of land in densely populated areas and weather factors in making podiums even more common now.

“In Chicago, real estate is expensive, and you don’t want to pay for a parking lot when you can put it under the building,” Blum said. “We see a lot of this in Wisconsin as well. With those Wisconsin winters, underground parking is definitely an amenity.”

Courtyard Included
BridgeWalk Apartments in downtown Waukesha, WI, meets many of those considerations. A $30 million complex along the Fox River, BridgeWalk includes 116 units with heated underground parking, along with a host of other features. Mid-States provided more than 43,000 square feet of hollowcore, beams, columns, precast wall panels and solid slabs for the podium under the apartment units. The U-shaped layout provides space for a courtyard green space atop the podium with dog walks and a grilling area. BridgeWalk does not include any retail, so the wood construction starts at ground level.

Tara Loomis, P.E., Mid-States Concrete senior structural engineer, said that BridgeWalk illustrates the versatility of podium construction and shows how engineers, architects and precast producers work together to solve issues.

“This is a large project that included podium elevation changes that needed to be customized in the plant during fabrication,” Loomis said. “We had to step our beams and step our planks down for the green space so they could get it built back up in those areas.

“The site also had a lot of water table issues, and they couldn’t drop the footings any farther, so the head height was really tight,” Loomis added. “We were able to adjust our beams and step our beams so that it all went correctly during the construction phase. It shows you the things we can do at the plant to get these elevation changes to work. All these things can be coordinated in the Revit (BIM) models, and the files are shared between the architect and the structural engineer to make sure all the steps are occurring at the right location.”

Mixed Use, Pedestrian Friendly
Mill District Apartments in West Verona, WI also features a U-shaped apartment structure with green space sitting atop the podium. Building AB is actually two L-shaped structures with green space and landscaping in between. Buildings C and D are also podium style. Krupp General Contractotrs is managing all four podium projects, with Mid-States providing the podiums. It is part of a mixed-use, pedestrian-friendly community hub that is a public-private partnership between the City of Verona and local real estate developers. Buildings AB and C are apartments, Building D includes a raised podium to include one story of retail at ground level with apartments above, for a total of 132 apartment units in the four buildings.

With an experienced team of erectors, podiums for projects like this can be set in a matter of a few days to a couple of weeks. Because the components are already fabricated and are shipped in from the precast plant, the scheduling is more certain. There’s no stripping of forms or waiting for concrete to cure. No weather delays. That kind of certainty creates an efficient construction schedule for contractors, according to Aaron Gundlach, senior project manager for Krupp.

“From a timing perspective, at least in our world, it is quicker than some other forms of deck,” Gundlach said. “It allows us to meet our schedules in a timely fashion. From a timing perspective, the precast podiums are very efficient – as efficient as anything else we would do.”

Total Precast
If a podium is loosely defined as a “platform,” then total precast structures could be considered along with the more common concrete base and wood tower configurations. Wright & Wagner Building C in Beloit, WI, illustrates that style. It is a slab-on-grade building with parking on the ground level and apartment units above. Built on the site of a former dairy, Wright & Wagner Lofts feature 54 units labeled as “industrial modern luxury.”

“This one is a little more unique because it's a total precast building,” Loomis said. “All the floors are precast. The first floor is beam-column-plank and wall panels. And then floors two through six are precast plank and precast ledger beams around the perimeter with Delta beams down the center.” Delta beams are steel beams manufactured to the depth of the plank to provide a flat ceiling. The building also features a cold-formed roof system.

Whatever final form a structure takes, podium-style construction is here to stay. Ideal for mixed-use buildings, apartments, hotels and multi-building campus developments, podiums use space wisely, provide amenities for residents and users and enable reliable, fast construction.

“It's a very efficient way to go at the end of the day,” Gundlach said. “It’s a good way to build these multi-story buildings and meet all the building design requirements, whether that be structural or area separations.  It allows us to build them fast and efficiently.”

Projects Featured

BRIDGEWALK APARTMENTS
Project Team
Architect: Striegel Agacki Studio
Contractor: Peridot Construction Management
Precaster: Mid-States Concrete
Erector: Mid-States Concrete

Building Details
Location: Waukesha, Wisconsin
43,062 square feet of Hollowcore
59 Beams
56 Columns
62 Wall Panels
3,173 square feet of Solid Slabs

MILL DISTRICT APARTMENTS
Project Team
Architect: Brownhouse Designs
Contractor: Krupp General Contractors
Precaster: Mid-States Concrete
Erector: Mid-States Concrete

Building Details
Location: Verona, Wisconsin
Building AB
26,116 square feet of Hollowcore
51 Beams
33 Columns
2,824 square feet of Solid Slabs

Building C
12,051 square feet of Hollowcore
16 Beams
12 Columns
278 square feet of Solid Slabs

Building D
17,848 square feet of Hollowcore
112 square feet of Solid Slabs

Wright & Wagner Building C
Project Team
Architect: JLA Architects
Contractor: Corporate Contractors Inc.
Precaster: Mid-States Concrete
Erector: Mid-States Concrete

Building Details
Location: Beloit, Wisconsin
74,048 square feet of Hollowcore
115 Beams
144 Columns
4 Balconies
61 Wall Panels
2,183 square feet of Solid Slabs