Potomac Center North, 500 12th Street, SW

The renovation and expansion of the Class "A" Potomac Center building was delivered in two phases.  The second phase focused on the north portion.  Like the previous expansion completed on the south portion, the existing structure on the north portion was eight levels above grade (291,000 gsf) and three levels below grade (151,000 gsf).  Approximately 229,000 gsf of new space was added through the application of both vertical and horizontal expansions.

Similar to the south-side portion of the project, the horizontal expansion added reinforced concrete bays to floors two through eight.  The flat plate design of the expansion was similar to the original structure in order to allow for proper ceiling heights.  The building was also expanded vertically by adding three steel-framed levels above the original roof level, plus a new roof and penthouse, matching the earlier south portion modifications.  The new upper levels were designed of composite steel, using 12-inch deep beams and girders in 20-foot bays in order to minimize the dead load added to the existing columns and foundations.  The foundations were upgraded using mini-pile underpinning.  

The entire facade was replaced and the core re-worked to accommodate new mechanical, electrical, and plumbing (MEP) systems.  Structural security features were also added to meet tenant and GSA requirements.