Doing up the dome
After almost 150 years, it’s about time this lady got some work done.
AWORLD-famous symbol of democracy will be under cover soon, as workers start a two-year, US$60mil (RM199.4mil) renovation of the US Capitol dome in Washington DC.
Curved rows of scaffolds, like Saturn’s rings, will encircle it in the coming months, enabling contractors to strip multiple layers of paint and repair more than 1,000 cracks and broken pieces. The dome will remain illuminated at night and partly visible through the scaffolding and paintcapturing cloths. But the Washington icon – and portions of the Rotunda’s painted ceiling that lies below – will be significantly obscured for many months.
The project is beginning just as the nearby Washington Monument sheds scaffolding that was used to repair damage from a 2011 earthquake.
Half-completed when US President Abraham Lincoln stood beneath it to summon “the better angels of our nature” in 1861 (when the American Civil War began), the Capitol dome has since towered over Washington, which limits building heights to under 40m. Time, however, has let water seep through hundreds of cracks. The water attacks cast iron, which “continues to rust and rust and rust”, says Stephen T. Ayers, Architect of the Capitol.
This first major renovation in more than 50 years should add decades of structural integrity to the dome, which Ayers calls perhaps “the most recognisable symbol across the globe”. The undertaking will heal inner wounds, he says, without changing the way the dome looks from the ground.
Much of the work will be done at night and on weekends. And it won’t be as flashy as the 1993 helicopter removal and return of the 5m Statue of Freedom from the dome’s top.
The Capitol’s crowning piece is actually two domes, one nested under the other like Russian dolls, and separated by a web of cast iron braces hidden from view. From the ground it looks like a massive structure that would be too heavy for the building to support if it were indeed made of the solid stone it appears to be.
Instead, it is cast iron painted to look like masonry. The lighter material and open space between the inner and outer domes create a physically sustainable structure. But it’s by no means puny.
The dome’s iron and masonry weigh 6.4 million kilos, says Kevin Hildebrand of the Capitol architect’s office. He recently led reporters up narrow, spiralling stairs that reach the Rotunda’s top and then give access to the in-between world of girders separating the two domes. Ultimately, the steps lead outdoors, to a panoramic walkway beneath the 12-columned lantern, or tholos, topped by the Statue of Freedom.
After a 1990 rainstorm left puddles on the Rotunda’s stone floor, workers found that bird nests had clogged gutters atop the Capitol, helping water penetrate outer walls and streak interior surfaces. Then they found bigger problems. Hundreds of cracks and pinholes in the cast iron exterior added to the seepage.
Pans now capture the water. Congress finally agreed to spend US$60mil (RM199.4mil) for a better, more lasting solution. “It is the symbol of our country,” Hildebrand says. “It is an icon that has to be preserved.”
The 150-year-old cast iron is lowquality by today’s standards, he says, adding, “it’s an archaic material.” A dome today probably would be built with glass and steel, he says. But Capitol workers must deal with relatively brittle iron that doesn’t respond well to welding.
First they must remove, capture and safely dispose of several layers of lead-based paint. When they reach bare iron, they must quickly prime and paint it section
by section, Hildebrand rust”