20 Massachusetts Avenue, NW | Washington, D.C.

With limited parcels available for new construction, the DC metropolitan area is experiencing a resurgence of adaptive reuse activity. To prepare the structure for additional floors, large atrium cutouts, and extending the building to the east, DPR reinforced the structure by:

• jacketing lower columns,
• adding shear walls,
• installing eleven 41-ft-deep micropiles below the garage’s slab-on-grade, and
• installing 80-ft deep micropiles on the east side.

Repurposing the existing structure saved 6,905 metric tons of CO2e, which is equal to emissions from 1,488 cars in one year, or the carbon sequestered by 114,175 saplings over 10 years.

Photo: Ron Blunt Photography

As a LEED Gold and WELL Silver certified property, 20 Mass was designed to integrate sustainable and tech forward components. The building had limited natural light due to its large floor plates. The team installed steel bracing and cut out large sections of floor plates to introduce two atriums—one 10-stories capped with a 2,400-sq.-ft. skylight and another rising four stories. This reduced the depth along all building sides, allowing for 60 additional guest rooms. The natural light highlights a 76-ft. by 15-ft. art installation featuring a map of Washington, D.C.

The buildings' sculptural glass top offers even more natural light with signature penthouse conference and lounge views. The atria slab cut outs and roof demolition generated 10,000 tons of concrete and other waste of which 75% was recycled. For other roof areas, a green roof featuring drought-resistant planting and an integrated stormwater management system reducing water consumption by 20% was planned.

Photo: Ron Blunt Photography

Located just one block from Union Station and four blocks from the US Capitol, 20 Mass is a key part of the Capitol Hill community, with an exterior that reflects the area's traditional architectural style. The complex curtainwall system features intricate details, including metal, glass, and terracotta panels, vertical fins, and shading.

During inspection, inconsistencies in the building floor plates resulted in a fanning effect. The team adjusted the curtainwall panels during production, and the column grid's fanning affected only eight of the more than 2,000 panels. Extensive testing of the concrete slab, floor levelness, and slab edge, along with mockups and performance testing of the curtainwall system, ensured the installation would be seamless and the building would serve the community for years to come.

Photo: Ron Blunt Photography

After demolition, a site survey and laser scan revealed inconsistencies in the concrete slabs, with variations of up to +/- two inches. DPR’s field technology group (FTG), virtual design and construction (VDC), and self-perform (SPW) teams overlaid a heatmap on the plans, enabling a cut and fill analysis to address the 1/8-inch tolerances required for the SurePods – prefabricated bathroom pods. SPW evaluated over 600 options to transition the SurePod and door frames into each room, considering materials, tolerances, and ADA requirements.

Photo: John Baer, Building Images Photography

It was discovered that the building’s north column grid rotated slightly, causing the columns to fan out as they progressed upward, with variations of up to +/- five inches. No longer providing a consistent stacking option, this required the guest room layouts to be adjusted, including the path for the installation of the SurePods. Instead of four layouts for the guest rooms there were now 40. Crucial to ensure the functionality of the guest rooms, modifications were made to each layout, removing wall setbacks and adjusting placement of furniture, factoring in hotel operations, including how rooms would be cleaned and maintained after occupancy.

Photo: Ron Blunt Photography

FTG and VDC used laser scanning, model-based coordination, virtual mock-ups, and visual planning to inform decisions and minimize time consuming and expensive changes in the field. A fully coordinated model resolved 2,900 issues.

Virtual mock-ups focused on the skylight, hotel rooms, curtainwall, and atrium, allowing quick design adaptations. The team evaluated the SurePod alignment, access panels for maintenance, fixtures, millwork, lighting, etc. For the curtainwall they looked for scope gaps and sequencing.

Physical and performance mock-ups were built. Three model rooms were constructed—one early in preconstruction, then two later confirming detailing. Models provided insight into design intent, constructability, and finish levels and addressed any existing conditions concerns.

Photo: Ron Blunt Photography

Prefabricated facade panels were crucial in enhancing worker and neighborhood safety, especially given tight site constraints, limited laydown areas, shared alleyways, and proximity to a historic building. Traditional construction would have significantly impacted the use and safety of a well-traveled pedestrian alleyway in the neighborhood. To address safety and to preserve the architectural vision, DPR’s self-perform work team (SPW) recommended prefabricating the panels within the footprint of the building onsite.

The virtual design and construction (VDC) team modeled the construction sequence to visually understand the efficiencies of prefabrication, provide a virtual mock-up of each panel, and demonstrate the sequence for safe installation. This approach eliminated the need for extensive alley and building protection, ensuring the safety of the alleyway and other work being conducted.

Photo: John Baer, Building Images Photography

The unitized curtainwall was prefabricated and delivered just-in-time for installation. Visits to fabrication plants ensured the curtainwall components captured the design concept of a pronounced base, middle, and top. The curtainwall was strategically articulated and recessed along different floors and facades, incorporating unitized terra cotta, deep aluminum fins, and vision and spandrel glass. To ensure quality, an 18-step performance testing process was initiated, with each step needing to pass formally before proceeding.

The project pioneered the use of SurePods in DC, streamlining construction and minimizing waste. 20 Mass was the first development in DC to use SurePod fabrication, significantly improving build quality. Factory-built custom bathroom pods, complete with Italian tile, vanities, and glass showers, were manufactured in parallel with the hotel’s construction phase. Twenty pods per day were lifted and set in place, reducing the schedule by 10%.

The fabrication of 206 pods took 42,700 hours. Each bathroom was connected to the MEP systems, completing the installation process. Rigging occurred on three sides of the building and through the 10-story atrium to coordinate with curtainwall installation sequencing.

Photo: John Baer, Building Images Photography