On the later additions, Quinn Evans Architects specified Hope Steel’s Landmark Series replacement windows, which closely matched the original Hope’s Steel Jamestown Series profiles and sightlines while adding thermally broken windows with insulated glass units. This overall approach was approved by the local reviewing agencies.
Masonry repairs are another area where architects often rely on specific products that are compatible with historic masonry. At the National Academy of Sciences, the Dover marble used on the 1924 section of the building is no longer quarried, so Dutchman patching, in which small areas of deterioration are replaced with new, carefully shaped masonry to precisely fit the removed masonry, with the same stone was not an option to achieve an acceptable match aesthetically. For this reason, the Jahn system, distributed by Cathedral Stone Products, was specified. Areas requiring a patch repair were filled using Jahn M120 repair mortar, a vapor-permeable mortar that is compatible with marble. Prior to installation, the subcontractor color-matched the mortar to be identical to the weathered appearance of the adjacent stone. Larger cracks in the masonry were grouted with Jahn M40 repair grout using injection ports. The cracks then were filled at the surface with the repair mortar.
Another historic project where materials were carefully selected and specified for their appropriateness is Eastern Market, also in Washington. Located on Capitol Hill, Eastern Market is a thriving center of economic and social activity. The market’s original South Hall was designed by Adolf Cluss, one of Washington’s most influential architects, and constructed in 1871. The market was expanded in 1906 by architect Snowden Ashford, creating the Center Hall and North Hall.
In 2005, Quinn Evans Architects began designing a comprehensive rehabilitation for this city-owned landmark, which had last been restored in the 1970s. On April 30, 2007, before construction work began, the market was devastated by fire, requiring additional and substantial restoration of the building. Quinn Evans Architects designed the restoration, which included a new roof, masonry repairs, new building systems, introduction of air conditioning and automatic fire-suppression systems.
The 1970s restoration had replaced the original galvanized cornice with a stainless-steel cornice, matching the historic profiles. Working from the 1970s drawings and elements remaining after the fire, Quinn Evans Architects specified Revere Copper’s TCS II, a zinc-tin-coated stainless steel as the new material for the cornice. One of the advantages of the zinc-tin coating is its ability to take paint, which allowed for a more accurate “sand finish,” intended to mimic the appearance of stone, to be applied. The TCS II product also was used for the decorative chimneys and acroteria elements on the roof that were restored based on historic photos.