Continuous Care of the U.S. Capitol Roof

The roof is the first line of defense against the elements for any building. And the copper roof of the U.S. Capitol — comprising about 200,000 square feet — is particularly vital because of the priceless art, decorative ceilings and the business of democracy housed beneath it.

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The copper has aged to a beautiful green patina over time; while it looks beautiful from afar, the roof needs constant attention and upkeep. That's where the Architect of the Capitol's (AOC) Capitol Building Sheet Metal Shop comes in, providing intensive labor and careful craftsmanship.

Much of the roof looks similar to the untrained eye, but each section was replaced at different times, the oldest section now dates back to the 1940s. A soldering date on each section marks the time when it was installed. The team recently replaced a section on the Senate side, between the cupola and East Front extension, which was installed in 1963.

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Copper roofing thins over time, and when holes are found, they are patched until the section is replaced.

Copper has been used as a roofing material for centuries because it is watertight and durable. Acid rain and the freeze-thaw cycle each winter wear at the copper. When the copper becomes too thin, tiny holes can form and let water in. There are nearly 100,000 small copper panels covering the roof. As part of the Capitol Sheet Metal Shop's ongoing preventive maintenance, the crew regularly walks the roof to clear drains and to look for broken solder joints, cracks and holes that need repair.

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Brian Jerdon bends a copper wall flashing.

The roofing copper comes in large sheets, some as big as 3 feet wide by 10 feet long. First, the sheets must be sheared down to the correct size. Then a stripe of solder is applied before the sheet is bent into shape, and finally cleats lock in the edges. This prep work is performed in the shop. Getting the copper up to the roof is its own challenge. The team has to be careful of their surroundings once on the roof, as there are different substrate surfaces and slopes to cross.

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Brian Jerdon installs a waterproof membrane before the copper wall flashing is placed at the base of the Senate cupola.

Before the copper flashing can be installed, a water-proof membrane is applied to protect the underlying roof from moisture, water and ice. This layer is tacky, self-adhesive and seals around any nail penetrations. The membrane is then covered in both felt and rosin paper before it is covered in copper.

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Kevin Golden soldering while Jason Stone and Darren Barnett install flat seam copper roof panels.

The roofing process has essentially remained the same as when the copper roof was installed in the 1940s, though some of the waterproofing materials and soldering tools have improved over time. The old way of soldering used copper irons heated with a charcoal pot. Now soldering torches with gas-burning nozzles continuously heat a copper iron, which is cleaner, safer and reduces the chance of starting a fire. "It's still just as labor intensive now as it was when the roof first went on," says Capitol Sheet Metal Shop Supervisor Bryan Glotfelty.

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Jason Stone, Brian Jerdon and Kevin Golden install flat seam copper roof panels.

The tent provides shade for both the workers and the copper. Copper holds heat, making it hot to the touch in the summer sun. The joints of the flat seam copper roof panels are soldered to ensure that the roof remains watertight. Well-soldered seams require a lot of skill. Fortunately, the Capitol Sheet Metal Shop has extensive experience with copper roofing. Of the 10 people in the shop, four are concentrated on the roof project.

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Kevin Golden and Jason Stone cover the newly placed copper with plastic sheeting at the end of their shift.

The shiny copper turns into warm brown pretty quickly in the rain. However, it can take 20 to 25 years for the natural weathering process to turn the warm brown tone into the distinctive green patina. The thought of rain midproject keeps Glotfelty up at night, "You're always worried about rain — once the old copper has been removed, the roof has to be covered with the waterproofing membrane and plastic and weighed down."

The U.S. Capitol's copper roof provides durability and longevity, with warmth and beauty, protecting everything inside the building. And it offers the Capitol Sheet Metal Shop a chance to shine and showcase their proficiency.

Like most beloved national treasures from the Golden Gate Bridge to the Statue of Liberty, the U.S. Capitol Building roof requires continuous care. Once a section has been replaced, it is regularly inspected as part of the shop's preventive maintenance.

When this section is complete, the crew will identify their work by soldering in the date to help a future Sheet Metal Shop team know when the work was done. And then they'll get started on the next section of roof.

Hidden History

You never know what surprise you may find just below the surface on any given project. When removing an existing section of copper roof at the northeast base of the cupola, the Capitol Sheet Metal Shop received an unexpected message from the past.

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The team discovered a handwritten note with the names of the workers who installed this section of the roof on September 29, 1963. The note was discovered lying under-neath a piece of copper on a sloped section of the roof.

Since the letter was hidden away for more than 50 years, the damage it sustained was minimal. It's a great testament to the expertise and superior craftsmanship of the workers. And finding it was a delight to those who are continuing the meticulous mission of maintaining the U.S. Capitol’s distinctive copper roof.