E. Barrett Prettyman U.S. Courthouse New Annex & Renovation - Washington, DC

ReStl Designers served as the Structural Engineer of Record for the renovation and expansion of the historic E. Barrett Prettyman United States Courthouse, a nine-story, 475,000 sq. ft. facility located just blocks from the U.S. Capitol. Originally built in 1952 and eligible for the National Register of Historic Places, the building underwent strategic renovations to preserve its historic integrity while maintaining full court operations.

The project also included the design and construction of a new 250,000 sq. ft. Annex, designed by Michael Graves, featuring multi-level courtrooms, judge’s chambers, administrative offices, two levels of below-grade parking, and a central atrium that connects to the existing structure through a series of architecturally exposed steel bridges.

The Annex structural system consists of cast-in-place concrete with flat slabs, concrete pan joists, and custom-framed barrel vault roofs. Critical structural elements included blast-resistant design, progressive collapse mitigation, and carefully engineered connections that allowed the new structures to slide independently of the existing courthouse to avoid transferring lateral loads. ReStl also addressed complex foundation and settlement challenges using a combination of auger cast piles, spread footings, and mat foundations.