One of the hottest buzzwords in architecture and construction today is "adaptive reuse" –
the process of adapting buildings that have outlived their original purposes into different types of structures, all while maintaining the building's historical character. Adaptive reuse is helping lead the revitalization of city centers across the country, as abandoned warehouses, factories and other historic buildings are being converted into residential and commercial space. In the city of Silver Spring, Maryland, just blocks from the District of Columbia line, the Gramax Building, a 15-story, 130,000-square-foot former office building, recently underwent such a change as part of the city's aggressive downtown revitalization plan.
Constructed of conventionally reinforced slabs and columns with a masonry shell, the Gramax Heliport Building, as it was formerly known, was built in 1964 and was originally the home of the National Oceanographic and Atmospheric Administration (NOAA). Upon NOAA's move to a larger facility in 1985, the Gramax Building sat vacant. After almost two decades of non-use, the building had fallen into disrepair and was somewhat of an eyesore on the southern Silver Spring horizon. However, as part of the Silver Spring revitalization plan, the building was slated to be converted into a high-rise apartment building for moderate-income residents. The renovated building would have 180 new apartments, and the ground levels would contain retail space and a fitness center, as well as an area for art exhibitions and a parking garage. Beyond its new offerings and amenities, the Gramax Building has been touted as the catalyst for the rest of the Silver Spring Revitalization efforts, as it was the first high-profile building on its block to be renovated.
Existing Conditions
Before repairs could begin, the cause of the deterioration had to be determined. The brick masonry façade had experienced deterioration as water penetrated the brick veneer and then underwent many freeze-thaw cycles. The upper and lower parapet walls also had deteriorated due to water entering through missing or damaged coping stones and undergoing freeze-thaw cycles. In addition, the masonry façade lacked adequate shelf angles and vertical expansion joints, and the floor slabs in the parking garage had severely deteriorated when standing water penetrated existing cracks and corroded the rebar. Finally, because of the change in use of the building, some structural upgrades were necessary, such as adding grade beams to support a new trash chute and adding strip footings to support several new CMU walls in the basement.
The owner and general contractor employed a specialty restoration contractor to perform the exterior masonry repairs, as well as extensive concrete repairs within the parking garage. Before work began, the structural engineer of record performed a visual survey of the masonry and a visual and sounding survey of the concrete to determine the scope of the necessary repairs. Upon completion of the survey and development of the initial schedule, it became apparent that the masonry façade restoration was critical to the project and a particularly important aspect of the overall renovation.
Repair Program
The initial survey determined that both the upper and second floor parapet walls were structurally deficient and needed to be completely removed and rebuilt. As part of the revised design, the new parapet walls were doweled into the existing slab and grouted at the bottom block course for added stability. This part of the façade restoration was completed first so the roofing contractor could follow with installation of the new roof. Upon completion of the new roof, swing stages were erected to allow access to the building façade for the remainder of the restoration.
A significant part of this restoration was the relocation of new windows. Many of the existing window openings were partially or completely filled with new masonry, and several new openings were cut on each floor to align the windows with the new floor plan. New steel lintels were placed atop all new openings. In addition, all observed cracked bricks were removed and replaced with new bricks, and all deteriorated mortar joints were repointed.
Inadequate expansion joints and a lack of horizontal relief angles in the original construction had led to some large bulges in several locations on the brick veneer. To prevent this problem from occurring in the future, new shelf angles were laid at every other floor, and new vertical expansion joints were cut in several locations. In order to install the new shelf angles, several brick courses were removed at the slab level of each odd-numbered floor, and the brick above was shored. New steel angles were then bolted to each slab and flashed, and new brick was laid. A soft joint was placed at the bottom of each new angle to permit vertical movement of the brick veneer. In addition, helical masonry ties were installed throughout the entire façade to stabilize the existing brick veneer. Vertical expansion joints were placed around the perimeter at a maximum spacing of 40 feet to allow for differential horizontal movement of the façade. The bulged brick was one of the last major repairs to be performed on the façade.
The brick bulge repairs were somewhat unique on this project due to the extent of some of the repairs. Different types of shoring were employed to maintain the structural integrity of the adjacent areas while the large bulges were removed and replaced. First, the bricks around the outside perimeter of the bulge were pinned extensively using helical masonry ties. Next, wales made of two-by-fours and threaded steel rod were installed around the perimeter of the opening to further stabilize the surrounding brick. Finally, the bulged brick was removed, and new brick was laid in its place.
Concurrent to the exterior façade restoration, the concrete repairs in the building's parking garage began. The initial survey revealed that more than 9,000 square feet – almost 40 percent of the elevated garage slabs -- needed to be either fully or partially replaced. During the concrete repairs, phasing and shoring were pertinent issues. Because of the extensive amount of full depth repairs required and the fact that the plumbing subcontractor was placing numerous trenches in the basement, intricate shoring plans were necessary to ensure that the building's structural integrity was not compromised during repairs.
The individual phases had to be large enough for the work to be performed efficiently, thus maintaining the overall project schedule, but not so large as to prevent other trades from working concurrently in adjacent areas of the garage. Conventional concrete repair methods were used for the garage repairs. Deteriorated rebar was sandblasted clean, and any rebar in the partial-depth repair areas that had lost more than 20 percent of its cross-section was replaced. In full-depth repair areas, the existing rebar was totally replaced other than the length required to achieve a full splice. Concrete pumps and buggies were used to place high-strength 6,000-psi concrete for the patches. Once repairs were finished, all garage areas were coated using an epoxy floor coating system.
Upon completion of the repairs to the elevated slabs in the parking garage, structural upgrades in the basement were performed. First, the areas for the new strip footings and new grade beams were laid out, and the slab-on-grade was removed by conventional jackhammers and remote-controlled demolition machines. The subgrade was then excavated to the appropriate depth, and rebar cages were installed. Finally, finished grades were established, and concrete was placed using motorized buggies. The completion of these new foundation elements allowed construction to continue on other items, such as the trash chute and new CMU walls.
The final significant step in the façade restoration, and arguably the most visible part of the overall project, was the coating of the entire exterior façade. The owner chose a color scheme and pattern, and two coats of a breathable, acrylic coating were applied to the building's exterior. In addition to enhancing the aesthetics of the existing building, this coating helps to conceal areas of new masonry in-fills, resulting in a more uniform appearance on the building façade. Even more important, the coating serves as a moisture barrier that will help to prevent future moisture-related deterioration of the masonry façade.
Project Success
The coordination of the various parties involved, including the general contractor, restoration subcontractor, structural engineer, architect, and numerous other subcontractors, presented one of the biggest challenges on this project. Many tasks required working over, around or below other trades. For example, in several instances, masonry façade repairs were halted to allow the demolition of new openings to proceed overhead. Significant coordination also was necessary between the restoration and window subcontractors to ensure that the sizes and locations of the window openings were in compliance with very exacting tolerances. All of the tasks on the masonry façade were coordinated while maintaining a tight project schedule and the strictest of safety standards, allowing the project to be completed ahead of schedule and within budget constraints.
The finished building is a highly visible and attractive structure credited as a leader in the Silver Spring Revitalization effort. As with so many other adaptive reuse projects around the country, the new apartment building will undoubtedly provide a significant economic and cultural boost to the surrounding neighborhood and continue to push the revitalization effort further toward the District of Columbia line.
About the Author
Matt Frye is a project manager in the Baltimore Branch of Structural Preservation Systems.