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U.S. Capitol Dome Restoration Project

The Dome of the U.S. Capitol Building, one of America’s great symbols of freedom, is currently undergoing a multi-year restoration.

The Dome of the U.S. Capitol Building, one of America's great symbols of freedom, is currently undergoing a multi-year restoration.

This project is a critical step for stopping the current level of deterioration in the Dome's cast iron as well as ensuring the protection of the interior of the Dome and Rotunda. The restoration project includes removal of old paint, repairs to the cast iron and stone, and repainting.

History

The United States Capitol Dome, symbol of American democracy and world-renowned architectural icon, was constructed of cast iron more than 150 years ago.

The U.S. Capitol was built atop Jenkins' Hill, now often referred to as “Capitol Hill” in 1793. Since then many additional buildings have been constructed around this site to serve Congress and the Supreme Court.

In accordance with the "Residence Act" passed by Congress in 1790, President Washington in 1791 selected the area that is now the District of Columbia to serve as the nation’s capital. French engineer Pierre Charles L'Enfant was charged with planning the new city of Washington. He located the U.S. Capitol Building at the elevated east end of the National Mall, on the brow of what was then called Jenkins' Hill. The site was, in L'Enfant's words, "a pedestal waiting for a monument." As the country grew so did Capitol Hill, with the construction of buildings housing the Congress, Supreme Court, Library of Congress and Botanic

The construction of the U.S. Capitol Building began in 1793, and for over a century it was the only building created for the use of the nation's legislature.

In fact, the Capitol initially housed not only the Congress but also the Library of Congress, the Supreme Court, the district courts and other offices. In the following decades the nation grew dramatically, and as a result, so did the Congress. The Capitol Building and its grounds were enlarged accordingly, and by 1892 the building had reached essentially its present size and appearance (with the exception of the east front extension [1958-1962] and courtyard infill areas [1991-1993]).

Importance

The United States Capitol Building is located in Washington, D.C., at the eastern end of the National Mall on a plateau 88 feet above the level of the Potomac River, commanding a westward view across the U.S. Capitol Reflecting Pool to the Washington Monument 1.4 miles away and the Lincoln Memorial 2.2 miles away.

At the U.S. Capitol Building the Senate and the House of Representatives come together to discuss, debate and deliberate national policy; develop consensus; and craft the country's laws. As the nation has grown so has the U.S. Capitol Building: today it covers well over 1.5 million square feet, has over 600 rooms, and miles of corridors. It is crowned by a magnificent white dome that overlooks the city of Washington and has become a widely recognized icon of the American people and government. The U.S. Capitol's design was selected by President George Washington in 1793 and construction began shortly thereafter.

Function

The U.S. Capitol Building is among the most architecturally impressive and symbolically important buildings in the world. It has housed the meeting chambers of the Senate and the House of Representatives for over two centuries. Begun in 1793, the U.S. Capitol has been built, burnt, rebuilt, extended and restored; today, it stands as a monument not only to its builders but also to the American people and their government.

As the focal point of the government's Legislative Branch, the U.S. Capitol Building is the centerpiece of the Capitol Campus, which includes the six principal Congressional office buildings and three Library of Congress buildings constructed on Capitol Hill in the 19th and 20th centuries.

In addition to its active use by Congress, the U.S. Capitol is a museum of American art and history. Each year, it is visited by an estimated 3-5 million people from around the world.

Deterioration

The Dome has not undergone a complete restoration since 1959-1960 and due to age and weather is now plagued by more than 1,000 cracks and deficiencies.

The Architect of the Capitol recently began a multi-year project to repair these deficiencies, restoring the Dome to its original, inspiring splendor and ensuring it can safely serve future generations of visitors and employees as the roof of the Capitol.

"As stewards of the Capitol for the Congress and the American people, we must conduct this critical work to save the Dome," said Architect of the Capitol Stephen T. Ayers, FAIA, LEED AP. "From a distance the Dome looks magnificent, thanks to the hard-work of our employees. On closer look, under the paint, age and weather have taken its toll and the AOC needs to make repairs to preserve the Dome."

Following a full and open competitive bidding process, a contractor was selected to perform the Dome Restoration Project. The AOC will supervise the project to ensure it remains on time and on budget. The project was awarded in November 2013 and preparation work began in January 2014.

Restoration

As scaffolding installation is completed on the Capitol Dome, the restoration work begins.

This repair work includes lead paint removal, application of primer coat, cast iron repairs, new castings, epoxy filling of pits and voids in the cast iron surfaces, window repairs and replacement, installation of fall protection and bird deterrent systems, application of intermediate and final paint coat, and finally scaffold removal. These tasks will occur from the bottom up – from the Peristyle to the Statue of Freedom. The final painting will be formed from top down along with

Four Major Steps in Restoration Repairs

1. Lead paint abatement and removal, ornamentation removal
The Dome is covered in multiple layers of paint that must be removed and remediated. This is conducted through special equipment that removes the paint via large tubes and sends it into special contained trucks located on the lower West Front. Ornaments and other loose pieces are also being removed during this time to be restored or recast at a foundry.

2. Prime cast iron
Cast iron "flash rusts" in four to eight hours once paint has been removed. Flash rusting is rapid corrosion that occurs instantly once metals are exposed to corrosive environments. Priming serves as a corrosion inhibitor by preventing oxygen interaction on the surface.

3. Lock and stitch, Dutchman repairs, ornamentation restoration
Each of the more than 1,000 cracks in the cast iron must undergo a mechanical technique called "lock and stitch." This is time-consuming work that must be done by hand. Each crack is drilled and special pins and a locking mechanism is installed. As the pins are tightened the cast iron plates are pulled together, or stitched, and then the screws are cut off and smoothed down. Additionally, "Dutchman" repairs will be made where large pieces are replaced with similarly shaped parts. Any recast ornamentation will also be reattached to the Dome.

4. Repainting
Following completion of repairs, repainting will occur. In total 1,215 gallons of paint will be used to repaint the Dome. This includes three layers, which uses 405 gallons each. The final topcoat color is "Dome White."

3. Lock and stitch, Dutchman repairs, ornamentation restoration
Each of the more than 1,000 cracks in the cast iron must undergo a mechanical technique called "lock and stitch." This is time-consuming work that must be done by hand. Each crack is drilled and special pins and a locking mechanism is installed. As the pins are tightened the cast iron plates are pulled together, or stitched, and then the screws are cut off and smoothed down. Additionally, "Dutchman" repairs will be made where large pieces are replaced with similarly shaped parts. Any recast ornamentation will also be reattached to the Dome.

4. Repainting
Following completion of repairs, repainting will occur. In total 1,215 gallons of paint will be used to repaint the Dome. This includes three layers, which uses 405 gallons each. The final topcoat color is "Dome White."

Progress

History of the
Capitol Dome