The Architect of the Capitol (AOC) is responsible for the preservation and maintenance of the stone exterior of the U.S. Capitol as well as the exteriors of all of the other buildings on Capitol Hill. As the buildings have aged, the challenge of caring for their ornate stone facades has only increased.
"Each of the buildings on Capitol Hill was carefully designed and built, and we need to make sure we preserve and maintain what others created for future generations," says Mary Oehrlein, AOC historic preservation officer.
The hands-on work caring for the stone found across Capitol Hill falls to AOC masons. These masons perform decorative brick, granite, marble and stone work including repairing stone and brick joints by cutting, raking, cleaning, and repointing with mortar and caulking compound. They also take care to mix color tone mortar to match the aging condition of work.
In addition, they re-construct falling or damaged marble cornices, cutting and replacing metal hangers, remounting, leveling and pointing up joints. They remove, repair and re-set marble moldings around doorways and are responsible for demolition and replacement of marble panels requiring metal hangers and plastic adhesive to re-set, in addition to finding durable matching stone.
On the Job
Entrusted with the care of the buildings and the safety of all occupants and visitors, the AOC has proactively worked to identify fissures and defects in the stone by conducting stone surveys and removing any stones that appear weak.
One of the challenges of caring for stone is keeping up with its maintenance. Various techniques are used to preserve stone, such as repointing, a procedure that involves removing the deteriorating mortar surrounding the stone piece and replacing it with new mortar.
The crew that makes up the AOC's Construction Division Stone Mason Shop is a roving group, working on projects throughout Capitol Hill, going wherever the need is greatest.
An AOC stonemason repairs the Olmsted Terrace.
One of the many projects they have tackled is the preservation of the low Olmsted boundary walls that ring much of Capitol Square. Completed in the 1870s by famed Capitol landscape architect Frederick Law Olmsted, the 5,500 linear feet walls made of granite and gneiss stone were in desperate need of repair. For a number of years, teams of stonemasons have worked to cut out the old mortar, reset the pieces and repoint the joints with new mortar.
"It’s a lot of work to make sure all of the joints line up," says Russell Jones, a stonemason at the AOC for the past 21 years. Aside from hard work, the project also required ingenuity and creative solutions. To duplicate the historic look of beading in the mortar, Jones created a custom-made tool to ensure all of the mortar appears uniform.
The complex nature of their work requires that the stonemasons seek assistance from other AOC shops. If they need a specialized piece of equipment or labor assistance, the shops are always willing to help, making the stonemasons' projects true team efforts.