The Natural Choice

From the time of the pyramids to the present day, architects the world over have chosen natural stone as a staple product in construction. Natural stone offers a certain image that no competitor can quite match, which is one reason it tends to show up on award-winning buildings. As a testament to this fact, several of the 2005 MCAA's International Excellence in Masonry Award winners employed natural stone for its lasting beauty.

For example, the first-place winner in the Industrial/Commercial category was the TPC Craig Ranch building in McKinney, Texas.

The TPC Craig Ranch design by Three Architecture, Inc. of Dallas uses the natural stone as the main design element; all other materials - slate roof tiles, stucco color and other elements - were selected after the stone. Robert "Rob" Barnes III, Executive Vice President of Estimating/Marketing with Dee Brown, Inc. in Garland, Texas, says that the design centered on three Oklahoma sandstone products.

"The owner, David Craig, selected the materials by traveling throughout Oklahoma, searching quarries to find the right mix," Barnes recalls. "The TPC - Tournament Players Club - had a say in the selection as well. After building the initial mockup, the materials were selected. Even so, the final blend and mixture of these three materials wasn't done until after we began installation."

Barnes notes that, other than maintaining the correct mixture of the materials, installation issues were few and far between.

"There was little challenge for us in procuring the material since Craig had pre-selected the quarries," Barnes says.

On the jobsite, the owner continued to be involved, discussing the project with the field foreman and making adjustments on how he wanted the stone laid. Barnes says, "He had our guys essentially lay the rock so that the face would move in and out more prominently."

Judges of the MCAA International Excellence Awards rightly cited the "overall craftsmanship to construct a project of this caliber" as a clear reason to award first place to the ranch project.

Barnes adds, "The battered columns and stone archway, outdoor full masonry fireplace and featured walls on the interior portion of the clubhouse were some of the elements that made this project special."

Higher Education

The mason contractor on this envelope-pushing project was Forrest & Associate, Inc. of Des Moines, Iowa. Dick Felice, President and CEO of Forrest & Associate, says the College chose Anamosa limestone, a dolomitic limestone, deposited approximately 420 million years ago across the Midwest during the geological Silurian Period of the Mesozoic Era.

"Anamosa limestone has a uniform texture, uniform banding, uniform color, durability and distinct delicate veining making it an ideal stone for building," remarks Felice. "The stone is locally quarried and is a traditional local building material, factors that entered into the decision as well."

But even though the stone was locally quarried, there were still challenges. "Providing the stone in the sequence and the quantity needed in a timely manner to allow the project to maintain the construction schedule was a concern," Felice comments.

Like the previous project, William Rawn Associates, Architects Inc. of Boston also used the natural stone as the main design element of the Grinnell College Residence.

"All of the exterior of the project is glass and stone, with stone being the vast majority of the exterior skin," Felice explains. "The color range of the stone is very narrow, which creates a singular visual impact."

Welcome to Baltimore

Unlike other typical building stones, however, there wasn't a great deal of precedence for using bluestone as building cladding. Typically, bluestone is used as an exterior paver for surrounding pools or placed on terraces. In most cases, the installation uses the common random sizes of natural shapes with a wide range of color. In this case, the architects were looking for large, rectangular panels with a very subtle color range. Locating the right quarry that could produce bluestone with these requirements and in the quantities necessary proved to be a significant challenge.

Another challenge arose during the joint work. The original intent was to use a colored mortar in the joints to match the understated tone of the stone. Using several mock-up panels, the architects observed that the bluestone had such a porous quality that it wicked the colored mortar into the perimeter of the panel.

"We set panels out for weather checks and monitored the 'aging' process," Harvey explains. "Our solution was to use a colored sealant that would additionally allow for movement with the stone. The final installation also contained a water sealant."

In the end, despite the challenges, bluestone proved to be an excellent choice for the Baltimore Visitor Center. With the site located on the West Shore of Baltimore's famous Inner Harbor, the stone's very subtle reflective quality enhances the building's appearance by creating a dramatic effect where the stone plays off its waterfront setting. The color range also works well with the main structure's palette of peppered granite, black slate, brushed aluminum, steel and glass.

Get Real
Why do leading architects and builders specify natural stone when so many alternate materials are available?

Perhaps the best answer comes from George James, General Manager of Cut Stone, of Indiana Limestone Company of Oolitic, Ind. - a city aptly named the "Limestone Capital of the World." In his view, natural stone is a natural choice simply because it's real.

"No one has been able to replicate true, natural stone," says James. "The nice thing about the real stuff is that every piece is unique unto itself. That's the way it was made, in our case, 350 million years ago when it was laid down in the shallow sea bed in what is now Indiana."

Another reason - especially for institutional buildings - deals with longevity. Government buildings, universities and most other institutional facilities are expected to last a long time. Architects for these structures want materials that will last equally long, with minimal maintenance.

"The perfect example of that is the courthouse, something that everyone expects to be there for over a hundred years," explains James. "We traditionally clad those buildings in limestone."

Another example is the Pentagon in Arlington, Va., where Indiana limestone was specified as the exterior cladding. When it was rebuilt after the attack on September 11, 2001 - which was, incidentally, on the 60th anniversary of the Pentagon's first day of original construction - Indiana limestone was found that perfectly matched the original.

Although it has been used for building since pre-historic times, stone still presents some challenges to the mason. According to James, every type of natural stone has its own set of specific requirements and challenges.

"Masons need to truly understand the material being put up," he explains. "For example, Indiana limestone, although it has virtually unlimited life as a cladding material, has corners that are susceptible to being chipped out if they're not handled properly."

However, once the limestone has been properly installed in the building, there is no reason that it shouldn't last hundreds of years.

"The bottom line is for masons to know what the particulars are on any given stone rather than one thing for all natural stones," James says.