The Expo at the World Market Center project added 315,000 sq ft of exhibition and conference room space to the center’s 5 million sq ft of showroom facilities. As the latest phase of the World Market Center, the Expo challenged the design team to maximize the building footprint within the limited site area without compromising critical transportation functions in front of the proposed Expo Hall. The solution was to tuck a large portion of the Expo floor under the existing seven-story parking garage, thus giving the project an additional 30% of floor area. The first floor of the parking garage then served as the roof of the new area while still remaining accessible for vehicle parking above. To accomplish this, the entire first floor of the garage was waterproofed with traffic coatings and the expansion joint assemblies were changed out. Extensive planning and testing were done to ensure the resulting building envelope was 100% watertight. That involved multiple charrette meetings among the contractors, design team and consultants, and was accomplished after several revisions to shop drawings and multiple rounds of water testing.