Natural stone creates iconic public spaces

by sadia_badhon | February 28, 2020 10:41 am

by Jason Kron

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Worldwide, cities are growing. Today’s megalopolis’ must not only provide its citizens with basics such as housing and transportation, but also with attractive public places for leisure time and city identification. Outdoor spaces transcending function and offering beauty and serenity in the bustling city landscape often become iconic. For thousands of years, natural stone has provided one of the best materials for creating outdoor spaces in cities.

Stone meets sustainability goals

For gathering places such as parks with fountains, memorial sites, and urban plazas, natural stone offers numerous benefits. It is a timeless, classic building material offering beautiful aesthetics and modern applications. Natural stone has one of the lowest embodied carbon levels among building materials.

Further, owners and designers can now specify sustainably certified natural stone options. Natural stone quarriers and fabricators with the “Certified Genuine Stone” label comply with the American National Standards Institute/National Stone Council (ANSI/NSC) 373, Sustainable Production of Natural Dimension Stone. The third-party verified ANSI/NSC 373 defines environmental, ecological, socially responsible, and human-health metrics for extracting and manufacturing natural dimension stone.

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Projects seeking green building certifications can choose certified natural stone to achieve their design goals. ANSI/NSC 373 aligns with materials and resource credits for U.S. Green Building Council’s (USGBC’s) Leadership in Energy and Environmental Design (LEED) v4 and the materials petal of International Living Future Institute’s (ILFI’s) Living Building Challenge (LBC).

Standing the test of time

Capable of withstanding the elements of weather and human interaction, natural stone performs well in urban hardscapes. A low-maintenance natural stone requiring minimal upkeep (e.g. granite) is a suitable material for public memorials. The Martin Luther King, Jr. National Memorial in Washington, D.C., Victory Memorial Drive in Minneapolis, and the East Tennessee Veterans Memorial in Knoxville, Tennessee, are beautiful civic tributes constructed with granite.

Structures built with natural stone more than 50 years ago remain standing today as a testament to the material’s resilience. One noteworthy example is the Air Force Academy Cadet Area in Colorado Springs (Denver), which was completed in 1958 and covers about a fifth of a square mile in the heart of the academy’s campus. It features concrete retaining walls finished with gray granite slabs.

As is noted in the National Historic Landmark Nomination[3], the retaining walls “accentuate the height of the plateau…[and] rather than blend the retaining walls into the colors of the earth, SOM [the project architect] chose to create an almost temple-like appearance. Architectural Forum declared that the architects ‘shaped the slopes as powerfully as the Babylonians, the Incas, and the Greeks once did.’”

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A similarly enduring icon is the “Word of Life” mural on the Hesburgh Library at the University of Notre Dame, Indiana. Completed in 1964, the mural is composed of approximately 6700 individual pieces of granite, in more than 140 colors. An article in the university’s journal, the Notre Dame News[5], emphasizes the durability of the granite and quotes Rev. Theodore M. Hesburgh, CSC, president emeritus of Notre Dame as saying, “The climate here is abominable at times and no one could say that it would last. The amazing thing is that it has lasted this long, and it has kept the richness of its color.”

The Franklin Delano Roosevelt Memorial on the National Mall in Washington, D.C., is another important symbol of civic pride featuring granite. For this project, sourcing American stone was a particularly important requirement. The memorial consists of 4-m (12-ft) high walls of rugged, split granite appearing as though they have just emerged from the quarry. The walls encompass four outdoor ‘rooms,’ signifying the four terms of Roosevelt’s presidency. Dedication of the memorial in 1997 marked the culmination of a 20-year effort.

In addition to providing a long-lasting building material, natural stone helps project teams create interesting frameworks for open and enticing spaces. With natural stone, design teams can:

• create a sense of place;
• provide a tactile experience for the public; and
• express the cultural and natural environment.

Sense of place

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The Denver Union Station is the nucleus of the city’s multi-modal transportation system, including commuter trains, light rails, and buses. Originally constructed in 1881, the landmark was recently renovated and reopened to the public in 2014. Surrounding the exterior of the project is a series of public spaces designed to connect the site and create gathering areas and event locations for denizens of Denver.

To create a sense of place, the project design team incorporated popup fountains where children splash and play in summer months. The fountain is computer-programmed to create numerous effects, and uplighting adds nighttime beauty. In winter, the inactive fountain leaves an unhindered hardscape area.

While sunshine, restaurants, and moveable chairs and tables characterize the south plaza, the quieter north plaza features raised perennial beds, abundant shade, and granite benches for seating.

Granite was a primary building material for the plaza, selected not only for its beauty, but also for its surface hardness and durability. According to the owner, the team achieved its goal of making the union station the most attractive public space in Denver.

Front door to the city

In many cities, natural stone can transform unused or underutilized spaces into vibrant public areas. Such was the case with the Dilworth Park project in Philadelphia, a revitalization of the city’s aging center square, formerly known as Dilworth Plaza. The design team transformed an inaccessible, multilevel plaza into a vibrant, open civic space. Situated above Philadelphia’s main transportation hub, the park also serves as a gateway to the city’s public transit.

Dilworth Park’s new design is a fusion of modern and historic, and granite plays a key role. According to the design team, granite was selected for its ability to provide a contemporary look while complementing the historic surroundings. Further, the design team noted the importance of using stone for projects because of its low embodied energy.

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Stone was a suitable choice for the new plaza’s surface, but designers were challenged with determining the best way to channel stormwater. The stonework had to maintain sufficient tolerance to achieve the required drainage characteristics. Exceptional fabrication with computer numerical control (CNC) technology achieved the precisely shaped stones meeting the specifications needed for drainage (See “CNC Technology Brings New Era of Stone Fabrication”).

CNC technology also allows producers to create shapes and designs in stone that were not possible even a few years ago. For example, curved stone walls can be more precisely cut, aligned, and joined together. Electronic files provide cutting details allowing even for the construction of sculpture and other art installations. Not only does the level of accuracy available when using CNC permit greater freedom of design, but also the ability to control the design concept from development through fabrication results in better project outcomes and quality control. The marriage of cutting-edge technology with the traditional material of stone allows for new paths of creativity, while the resulting designs maintain a time-honored, classic feel.

Cultural and natural environment

In St. Louis, Missouri, Citygarden provides an excellent example of urban revitalization as new generations develop an appreciation for downtown living and amenities. Designed to provide a vibrant and serene urban oasis, and funded by the Gateway Foundation, Citygarden sits at the heart of the Gateway Mall just a few blocks west of the famous Gateway Arch and Mississippi River. The redesign developed Citygarden from a two-square-block space that was underused for decades and often sat idle as an open lawn.

CNC TECHNOLOGY BRINGS NEW ERA OF STONE FABRICATION

Computer numerical control (CNC) technology has made its mark on stone design and fabrication, providing numerous benefits to those who take advantage of its capabilities. With computers controlling the machines, stone fabricators produce intricate, inspiring creations with exact precision once thought impossible or too costly to achieve. As a result, architects and designers are expanding their creative limits and experiencing many benefits including: increased freedom of design; control of the design concept from development through fabrication; quality control; and accuracy of stone shaping and the final fit and finish. Despite CNC’s benefits, many design professionals hold misperceptions about the process. Chief among the misconceptions is CNC is only used for granite slabs. It is often difficult to imagine a computer-controlled machine handling a large block of stone and producing the result of a finely trained sculptor with a chisel in hand. Quite the opposite, CNC machines can accept both slabs and cubic stones of all sizes with ease, depending on the type of machine type. Another misperception is the CNC process is not budget friendly. Although CNC technology is advanced, it is not cost-prohibitive. Historically, large profiled stone components and cubic free-form shapes were labor intensive to produce. Today’s designs, in most cases, begin as a digital project in one of the many computer-aided design (CAD) or digital design tool software packages. Using this ‘master model’ format, the fabricator realizes lower costs since much of the drafting work required for the old manual method is eliminated. Further, CNC achieves a very fine tolerance, reducing the need for multiple or follow-up processes. Fabrication and lead time are reduced, and custom designs are easier on the budget.

The foundation and City of St. Louis wanted the garden to embody a timeless quality evoking the city’s history and spirit. The selection of natural stone for this project was instrumental in obtaining that quality. The foundation wanted to ensure the park would not be dated and would remain durable for decades to come. As such, the selection of granite, limestone, and bluestone provided the durability to withstand harsh environmental elements and heavy use, while also creating a dramatic and aesthetically pleasing visual effect. The foundation liked the use of limestone native to the area for sustainability purposes and its ability to help knit the garden to its regional geology. The granite color selections complement the glass pavilion café in the northeast quadrant of the garden. Totally, the project encompasses 3345 m² (36,000 sf) of granite in paved areas.

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Citygarden is structured as three precincts delineated by two walls. The northern precinct represents the high upland ground and the river bluffs. The middle represents the low ground or floodplain. The southern band represents the cultivated river terraces. While all the territories are interrelated and interconnected, each precinct possesses distinct characteristics. The first wall, granite-capped and offering seating, snakes through the park’s southern portion. The arcing second wall measures 168 m (550 ft) long and is constructed of Missouri limestone.

While providing park space, Citygarden also serves as a sculpture garden including 24 modern and contemporary works. Other features include a massive ‘spray plaza’ and a split-level pool whose two parts are joined by a waterfall. The project has won the Urban Land Institute Amanda Burden Urban Open Space Award. The award is designed “to recognize an outstanding example of a well-used public open space that has spurred regeneration and the transformation of the surrounding community.”

During the opening ceremony for the park, Mayor Francis Slay said, “With one stroke, Citygarden has made downtown so much more attractive as a place to do business, and as a place to live, too.”

Durability and performance

The city of Cincinnati, Ohio, has used stone so abundantly in its public spaces and city landmarks that a paper highlighting this use of stone[9] was published in celebration of Earth Science Week 2000. The paper, formatted as a walking tour celebrating stone as a natural resource, highlighted the extensive use of granite, including in the city center’s Fountain Square where Bavarian igneous rock composes the fountain itself. Both polished and unpolished granite elements  are used for paving, benches, stairs, railings, and a performance stage.

More recent developments in Cincinnati have continued to rely on stone as a durable, aesthetic building material. A transformation of the city’s riverfront began in 2008 when a piece of once-dormant land was envisioned to become the region’s new gateway. The project was a response to redevelopment of a 1960 interstate expressway that had consumed a huge swath of riverfront acreage and severed access between the city’s downtown and riverfront.

Construction on the riverfront started with the 18-ha (45-acre) Smale Riverfront Park and adjacent 7-ha (18-acre) development known as the Banks. The park design accommodated the area’s inevitable flooding as well as provided durability in the face of aggressive winter de-icing. Designers selected materials that would minimize ongoing maintenance and also provide a long-term cost advantage, with initial incrementally higher prices being offset by lower repair costs later. Granite was chosen for a grand stairway and bicycle ramp not only because of its resistance to salt and flood damage, but also for its color and texture that would enhance the park’s visual appeal.

Conclusion

The creation of a public space is an important task leaving a lasting imprint on a city’s legacy. Perhaps, the noted landscape architect Carol R. Johnson sums it up best: “A great event is not made out of any of these details: it is just a layer of enrichment in a whole experience.”

[10]Since 1999, Jason Kron has specialized in the natural stone industry. In his current role as director of sales at Coldspring, Kron works with the architectural and design communities to meet their natural stone needs and with cemeteries for product and development needs. He can be reached via e-mail at jkron@coldspringusa.com[11].

Source URL: https://www.constructionspecifier.com/natural-stone-creates-iconic-public-spaces/

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