Marking history with Indiana limestone
The National Constitution Center was established by the Constitution Heritage Act of 1988, which was passed by Congress and signed at the time by President Ronald Reagan. The Act created the Center as an organization and first established building the facility as an important national goal. On September 14, 1998, the architectural firm of Pei Cobb Freed & Partners and the exhibit design firm Ralph Appelbaum Associates -- both of New York -- were commissioned for the project, which is the first museum devoted to honoring and explaining the U.S. Constitution. The design of the 285,000-square-foot building was conceived by Henry N. Cobb with partner Ian Bader, along with exhibit designer Ralph Appelbaum.
And while the building’s design was applauded by architectural critics, it does veer away from the traditional red brick found in the majority of neighboring structures. But the soft tones of Indiana limestone, which are broken up by 8-inch-high bands of light gray-colored Chelmsford granite -- create an unobtrusive design that meshes well with the surrounding environment. Introducing the granite bands into the design of the exterior facade helps to provide a less formal look -- reducing the scale of the structure and emphasizing its horizontality.
Complementing the stonework is a two-story glass entrance, which is called the “front porch” by Cobb. As Cobb told The New York Times, “It couldn’t be too official. It’s not a government building. Nor could it be extremely monumental, since it is neither a museum nor a shrine. It had to be more relaxed.”
In total, 10,000 cubic feet -- 33 semi-flat truck loads or 3,600 pieces -- of Select Buff limestone from Indiana Limestone Co.’s PM&B quarry in Bedford, IN, was used for the exterior. The average panel size measured 4 feet, 8 inches x 3 feet, 4 inches.
“We use a great deal of the material,” said Project Architect Craig Dumas of Pei Cobb Freed & Partners. “We’re very familiar with it. One of the big advantages is that it can be a consistent stone with a warmth to it, and it’s relatively inexpensive. We used a higher grade to get the consistency, and buff for the warmth.
“We complemented that warmth with alternating 8-inch-high horizontal bands of Chelmsford granite,” the architect continued, adding that this material was supplied by Fletcher Granite Co. Inc. of N. Chelmsford, MA. “We looked at other granites, but knew that we wanted to use granite because we wanted to use [the same material] for the paving and base as well. We needed a harder stone.”
The architect went on to explain that the original stone treatment for the National Constitution Center varied slightly from what actually was constructed. “We initially went to Indiana limestone, but we wanted to have ribbed vertical on the surface of the stone -- to give texture,” said Dumas. “There was quite a lot of detailing that went into that. Shortly before the drawings went out to bid, we had a full-size mockup on site, with corner detailing and such, so we could make sure everyone was happy with the full scale. In the end, the owner didn’t like the ribbed texture, because it looked too much like pre-cast concrete. The owner thought it eliminated the natural veining and coloring of the natural stone -- it ended up being too consistent. We actually ran around in circles looking for other stones with more character, but that maintained the same likeness in color and warmth.” But in the end, the decision came back to use Indiana limestone. “In the end, we and the owner were satisfied that it had enough lively character.”
The quarry where the Select Buff limestone was produced has been in continuous operation for over 120 years, according to Chief Executive Officer Rick Johnson of the Indiana Limestone Co. “The stone is a favorite,” he said. “A lot of it has history from back in the 1800s -- it’s kind of a standard. Other monumental buildings have been done out of here, including the Empire State Building, the Pentagon and a lot of courthouses as well as 17 state capitol buildings. Using Indiana limestone fits this monumental building. It’s a big important national building. It really has a contemporary look, but it’s also traditional.”
The exterior pieces were fabricated at the company’s facility in Bedford. It required about three months or 4,000 man-hours to complete, according to George James, general manager. “We run anywhere from 6 to 20 different jobs at a time,” he said. “This project was integrated into that load.”
James spoke complimentary of the integration of the limestone with the granite. “It really does give a flavor and richness in color as well as depth,” he said. “When you step back, you really get a feel of the versatility and durability of the limestone accented with the granite.”
One particularly striking element of the exterior stonework is where a few lines of the Constitution, beginning with “We the People of the United States,” was etched into one of the main facades. “We actually carved in the outline of the preamble of the Constitution and at the jobsite stainless steel was inserted,” explained Sales Manager Duffe Elkins. “It’s a distinctive feature of the building.”
The exterior stonework, including the granite pavers, was installed by Lepore/Mark Contractors Joint Venture of Conshohocken, PA. Turner Construction of Philadelphia was the general contractor for the job.
Interior stone panelsAs is the case with many projects, budget was a concern for the owner and architects. As a result, an alternate solution had to replace initial plans for the interior design of the two-story lobby. “Originally, we designed the walls to be solid stone,” said Project Architect Craig Dumas. “Unfortunately, when the drawings went out to bid, it was a ‘hot time’ on the market, so we had to cut costs. The general contractor offered savings by using lightweight stone panels.”
The lightweight stone was fabricated from the same Select Buff limestone and Chelmsford granite that was employed for the exterior. Indiana Limestone Co. and Fletcher Granite supplied slabs to Stone Panels Inc. of Coppell, TX, who in turn produced the Ultra-Lite Stone wall panels, which weighed only 3 1⁄2 pounds per square foot.
“Ultra-Lite Panels are an alternative to solid heavy stone,” said Craig Carroll of Stone Panels Inc. “Solid rough sawn slabs of limestone were sandwiched between two 3⁄4-inch-thick pieces of aircraft quality aluminum honeycomb by adhesion, using a proprietary high-strength, fiber-reinforced epoxy. After curing, the slabs were cut through their center thickness by a diamond tip saw, resulting in 1⁄4-inch stone thickness.”
This patented manufacturing process offers substantial impact resistance and flexural strength, according to Carroll. The fiberglass skins directly behind the stone provide an impermeable waterproof barrier, which eliminates the necessity for a secondary water barrier.
Approximately 20,000 square feet of Ultra-Lite limestone was installed as interior wall panels. It included various angled corners, plus both convex and concave curved panels, which were installed over steel stud framing by Dale Construction Co. of Glenside, PA, said Carroll.
Dale Construction also installed approximately 9,000 square feet of Ultra-Lite limestone panels on the upper exterior walls over the atrium.
“This was somewhat new for us,” said Dumas. “We had done limited applications like this before.” To ease some of the design team’s reservations, the architects visited a number of installations that had employed Ultra-Lite Stone panels. “In the end, it was a pretty efficient system,” said the architect.
Although expense was an issue, the budget did permit for solid granite to be used for the fronts of ticket and information desks inside the museum. Additionally, granite was employed for a number of benches, which recognized donors, a grand stair, and slabs of the material were used as borders for the terrazzo floor. All of the dimension stone installation was completed by Lepore/Mark Contractors Joint Venture.
Groundbreaking for the National Constitution Center was held on September 17, 2000 -- 213 years to the day the U.S. Constitution was signed. President Bill Clinton presided over the official ceremonies, which included the naturalization of 75 new American citizens and the announcement of a $10 million gift from the Annenberg Foundation. According to Dumas, construction lasted about 27 months, although there was a hiatus of about six months between bid and the start of construction.
When the museum opened on the Fourth of July of this year, national, state and local dignitaries came to celebrate, as well as more than 22,000 visitors from across the country. An approximate 1 million visitors are expected annually.
Upon seeing the results, all those involved have expressed delight with the project. “We were quite sure what we wanted to do,” said Dumas. “It was a bit of an adventure getting the owner on board.”
End boxArchitects: Pei Cobb Freed & Partners, New York, NY; Ralph Appelbaum Associates, New York, NY (exhibit design)
National Constitution Center, Philadelphia, PA
General Contractor: Turner Construction, Philadelphia, PA
Stone Quarriers: Indiana Limestone Co., Bedford, IN (limestone); Fletcher Granite Co., N. Chelmsford, MA (granite)
Stone Fabricators: Indiana Limestone Co., Bedford, IN (exterior limestone); Stone Panels Inc., Coppell, TX (Ultra-Lite Stone wall panels); Granit Bussiere, Quebec, Canada (granite)
Stone Installers: Lepore/Mark Contractors Joint Venture, Conshohocken, PA (exterior stonework/interior dimension stone); Dale Construction Co., Glenside, PA (Ultra-Lite Stone wall panels)