SGH acquired this project as part of our acquisition of Keast & Hood’s Washington, DC, office. Keast & Hood was responsible for the project through early construction administration and SGH completed construction administration. At all times, Matthew J. Daw, former employee of Keast & Hood and current employee of SGH, was the principal in charge of the project.

Highlights of our design of the vertical expansion include the following:

• Limiting the height of the new penthouse to satisfy zoning requirements

• Locating new structural steel at the same level as the building’s existing wood-framed roof to meet height restrictions and maintain a watertight building

• Supporting the framing on existing mass masonry perimeter walls between windows and using concrete bearing pads to distribute the load to meet the existing brick masonry’s allowable compressive strength

• Detailing horizontal tie rods to resist lateral thrusts from the sloped mansard roof and fit within the depth of the existing fourth floor structure

• Threading new steel behind the existing structure through isolated openings in the existing roof to limit impacts to the mansard roof framing and avoid making access points in the brick masonry walls

Despite challenges, including a congested urban environment, height restrictions, and schedule limitations, the team completed the project prior to the museum’s 2018 Summer Housewarming Celebration.