Renovated Sherman Building. Photo: Keast & Hood
Structural distress caused by the Aug. 23, 2011, Mid-Atlantic earthquake forced the closure of the landmark Sherman Building at the Armed Forces Retirement Home in Washington, D.C., for the first time during its centenary history. It is now back to full force, thanks to a careful restoration, serving as a model for other similar projects.
Gable end masonry damage. Photo: Armed Forces Retirement Home
Constructed in three phases between 1852 and 1891 at the sprawling 272-acre federal campus used as a retirement community for U.S. military veterans, this impressive structure served as dormitory, dining hall, library, billiard hall, post office, barber shop, and canteen since opening in 1857. Today, the building is the centerpiece of the U.S. Soldiers’ and Airmen’s Home National Historic Landmark.
Steel structure inserted to strengthen tower. Photo: PRESERVE/scapes
Designed by Lt. Col. Barton Alexander and built by Gilbert Cameron from 1852-1857, the Sherman Building was originally a two-story masonry structure with a modest tower. Between 1868 and 1871, Architect of the Capitol Edward Clark designed a third floor addition with a Second Empire style mansard roof and added a tower clock. The building’s final phase of construction occurred from 1887-1891. Architect William M. Poindexter and Co. replaced the mansard roof with distinctive ornamental parapets and turrets in the Richardsonian Romanesque style. This phase included construction of the north wing and extension of the clock tower to its final height of 130 feet.
Post-earthquake parapet damage (left) and repaired parapets (right). Photos: Armed Forces Retirement Home and PRESERVE/scapes
The 5.8-magnitude earthquake of 2011 had an epicenter near Mineral, Va., causing damage throughout the Mid-Atlantic region. The Sherman Building was significantly affected, with hazardous conditions created by fallen stones and structural distress. After 160 years of continuous use, the Sherman Building was vacated for the first time in its history.
A two-year earthquake recovery project both restored the Sherman Building’s iconic structure and serves as a model for how a dedicated team can transform devastation into opportunity for preservation, innovation, education, and stewardship.
Working for the U.S. Department of the Treasury, Bureau of the Public Debt and the Armed Forces Retirement Home, a design-build team led by The Christman Company (general contractor) included Keast & Hood (structural engineer), Quinn Evans Architects (architect), and PRESERVE/scapes (preservation consultant). The team worked collaboratively to repair earthquake damage and remediate structural conditions.
Recovery in detail
Stone masonry unit placement. Photo: PRESERVE/scapes
At the start of the project in July 2012, the full extent of damage to the Sherman Building was not known. Visible conditions included hundreds of fallen and removed stones, gaping holes in the roof, collapsed retaining walls, and destroyed interior finishes. But substantial cracking and displacement of masonry were symptoms of extensive structural damage.
For a project defined by unforeseen conditions and historic significance, the team implemented an approach that allowed for the fluid development of designs and methods tailored to the building’s unique historic construction and fabric. Every member of the multi-disciplinary team, from consultants to contractors, worked closely in the field, fostering a collaborative spirit and collective vision for recovery. Through this concerted effort, the team maintained a fast-track schedule and stayed within budget, despite project complexities. The Armed Forces Retirement Home moved back into the building within six months of the start of the design-build process, and all work was completed in just over a year.
A major component of the Sherman Building project was substantial masonry reconstruction to repair structural damage and to provide concealed reinforcements for sensitive seismic retrofit and long-term preservation. Much of this effort focused on the building’s iconic clock tower; more than 500 stones (20 courses) were reconstructed around a new steel frame carefully designed to be hidden within the tower’s open belfry.
Renovated Sherman Building clock tower. Photo: Keast & Hood
The original clock tower was elaborately and beautifully constructed out of mostly single-wythe stone masonry, which had weathered well but performed very poorly in the earthquake. On the project critical path, a steel-braced frame was selected to reinforce and add stiffness to the exposed bell level of the tower without adding significant weight and triggering further reinforcing or foundation upgrades below. The columns, beams, and braces of the frame were carefully located and later painted to avoid visibility from exterior views of the tower.
Limited interior stainless steel reinforcing and masonry backup were added to provide load transfer and strengthen weak points in the reconstructed stone masonry. The tower roof was constructed to match the existing form while providing capacity to brace the tower parapets and transfer diaphragm forces.
In total, 3,037 stones in the building’s parapets, chimneys, and retaining walls were accurately reconstructed, reusing 98 percent of the original pieces of hand-carved marble in their original locations.
In addition to masonry reconstruction and embedded reinforcement, the recovery project required anchorage of exterior masonry walls to floor diaphragms, heavy-timber truss and roof repairs, and restoration of finishes and features, including more than 1,500 linear feet of cast iron railing.
To accomplish these tasks, the team implemented innovative methods that serve as models for future preservation projects. A comprehensive point cloud survey and iPads were critical to in-field documentation and assessment. The survey ensured that the design for structural remediation was tailored to the unique geometry and conditions of the tower. Digital surveys and custom graphic tools, such as course maps and inventory elevations, resulted in improved efficiency and 100 percent accuracy for the complex reconstruction.
One of the more exciting unforeseen conditions was a time capsule found during deconstruction of the tower. The time capsule artifacts, left by the original masons in 1890, were conserved and returned to the tower during a December 2012 topping-out ceremony. The discovery of the time capsule and artifacts, including original mason’s markings and tools, fostered immense pride in the team’s efforts to restore the legacy of the original tradesmen.
The team’s efforts reached beyond the building itself. The project created opportunities to engage the community and provide exposure to a historic landmark that is not open to the public. In addition to writing articles to keep veteran residents engaged in the recovery, programs were conducted with community groups, and presentations and tours were hosted for professional organizations.
Working with the nonprofit Live It Learn It, the team orchestrated an interactive educational program for local elementary school students. The program explained the historic significance of the Sherman Building; gave students the opportunity to play the role of engineer, architect, or builder to create a replica of the tower; and introduced students to careers they might one day pursue.
Spirit of stewardship
In August 2013, the Armed Forces Retirement Home hosted a public open house to celebrate the project’s completion and created a permanent lobby display to educate staff, residents, and visitors about the building’s history and recovery. The rebirth of this landmark has renewed a spirit of stewardship and preservation, one that will surely have a lasting effect on the building and the surrounding historic campus.
Craig D. Swift, S.E., LEED AP, is an associate with Keast & Hood structural engineers in Washington, D.C.
Carrie Barton is owner of PRESERVE/scapes, a historic preservation consulting firm located in Washington, D.C.