Kelley Drye & Warren LLP
Monumental Stair

Kelley Drye & Warren LLP’s new Washington, DC, office is a 65,308 sf, three-floor interior fit-out located at 670 Maine Avenue, overlooking the Southwest Waterfront. At its heart is a monumental stair connecting Levels 5 through 7 via a three-story opening. The opening’s location was driven by architectural layout rather than structural efficiency. It disrupted primary post-tensioning tendons and removed the backspan of a 15-foot slab-edge cantilever above an intricate façade with deflection limits far tighter than those required by code.

The opening was refined to preserve as many primary tendons as possible, followed by a sequenced process of shoring, tendon lock-off, cutting, and re-tensioning. Continuous slab-edge monitoring kept deflections within the façade’s limits throughout the process. The stair’s kinked stringers use shallow, heavy-wall HSS members designed to resist torsion, while bent-plate treads provide stiffness, allowing the stair to function as a self-supporting structure. Reworking the existing structure rather than adding new framing, along with using recycled-content steel and CarbonCure concrete, also advanced the project’s sustainability goals.