The Preserve Buildings 4, Oak Island NC is approximately 90,000 sq. ft 4 story tall luxury condominium building part of approximately 400,000 sq. ft complex. The Architect of Record is Darryl Barker of Wilmington, NC. The structure features a combination of reinforced concrete frames and shear walls supporting two-way post-tensioned (PT) flat plates. Using 8” and 10” thick PT slabs allowed the Owner to achieve 5 floors and minimum 9’-0 ceiling height at each level all fitting within the maximum permitted building height. In addition using post-tensioning made possible to span 28 to 32 ft. while maintaining long term deflection and stresses within the code permitted limits. All stabs were designed in house including punching shear checks and detailing. The seismic site class was initially determined as “F” by the project Geotechnical Engineer, therefore the site had to be remediated with vibro-compaction stone columns and earthquake drains. The building is supported on combination of strip and spread footings. The project was completed in 2006.