Terrazzo Renewal
TECHNICAL CONSIDERATIONS FOR TERRAZZO FLOORING
A. Epoxy vs. Cement-Based Terrazzo Systems
Today, epoxy terrazzo accounts for approximately 95 percent of current interior installations, replacing the traditional cementitious terrazzo, which, with a sand cushion, is unsuitable for retrofit due to its thickness. The monolithic and bonded cement-based systems are thinner options. First used with terrazzo in the 1960s, epoxy is relatively thin, lightweight, extremely durable, and sustainable and offers the quickest pour-to-grind installation time and unlimited design options.
Epoxy terrazzo is a nominal 1⁄4- or 3/8-inch-thick resin matrix veneer placed on a prepared, flat concrete slab. It can be specified with glass, synthetic, to provide brilliant colors or chemical resistance, marble, or other natural stone aggregates. Recognized as the best general interior-use thin-set system, it offers unlimited custom matrix colors, color control, resiliency, flexibility for patterns, chemical resistance, and tensile-compressive strengths not found in cement-based systems.
Epoxy terrazzo is likewise lightweight (approximately 4 PSF for 3⁄8-inch thickness) versus 1/2 inch for the traditional cement-based monolithic system or three inches for the sand-cushion system. Epoxy is somewhat flexible, making it ideal for multistory use. It is commonly applied with a flexible membrane to absorb horizontal concrete cracking or control joint movement.
B. Rustic Terrazzo for Exterior Paving
Rustic terrazzo offers custom options for exterior paving. A cement system typically specified for on-grade outdoor applications, it is commonly used for floor and wall surfaces of swimming pools, walkways, patios, steps, and plazas. The textured, nonslip finish is resistant to extreme weather conditions. It is installed as a half-inch topping bonded to concrete.
Rustic Terrazzo:
- Design-versatile and adaptable to any architectural style, from classic traditional or artistically complex designs.
- The unpolished, non-slip surface showcases the texture and colors of each stone.
- It can depict almost any logo, figure, or pattern for branded or themed spaces.
- It provides more design and patterning options than an exposed aggregate concrete finish and has a more refined, consistent aesthetic.
MAUMUS CENTER: HISTORIC SCHOOL REINVENTED POST-KATRINA WITH MULTIPLE TERRAZZO SYSTEMS
Photo courtesy of David Laudadio
Maumus Center’s terrazzo systems, including a Milky Way Galaxy in epoxy and a sun calendar in rustic terrazzo, redefine the space.
Initially built in 1929 as the first public high school in Arabi, Louisiana, the Maumus Center building had evolved through various reincarnations, including a Red Cross shelter. In 2005, after continually serving the community, generation after generation, the New Orleans suburb’s treasured landmark was decimated by Hurricane Katrina.
Due to regulations, serving as a school was no longer an option, so the St. Bernard Parish school board settled instead on creating a science learning center with a planetarium and interactive museum to serve the entire district. In 2015, the major conversion of the historic building was completed, prolonging its lifespan while improving its functionality.
The Maumus Center project encompassed a whole gamut of terrazzo systems, providing the durability and design flexibility needed, said architect Emily Palumbo of Waggonner & Ball. That choice “allowed us to respect and complement the type of building it was,” she explained.
The design responded to existing materials while creating highly distinctive features in the center. The sun, moon, and stars are built right into the floors at the new center. Spreading wide in the lobby is a sparkling representation of the Milky Way Galaxy in epoxy terrazzo. An outdoor learning area is equipped with a functional sun calendar set in rustic terrazzo that accurately indicates time and date with a beam of sunlight through an oculus in the roof onto brass markers embedded in the floor.
This 15,800-square-foot installation in 18 colors is a captivating demonstration of the potential of terrazzo and a model of skilled craftsmanship. Various appropriately placed and scaled elements come together in a design that successfully blends simplicity with high impact.
The American Institute of Architects honored New Orleans architects Waggonner & Ball with a Merit Award for Adaptive Reuse for the project. Furthermore, the project earned an Honor Award from the National Terrazzo & Mosaic Association for the terrazzo contractor, Terrazzo Masters of Metairie, Louisiana.
Illustration courtesy of National Terrazzo & Mosaic Association
Epoxy terrazzo, with a thin ¼-inch or 3/8-inch resin veneer, offers vibrant colors and chemical resistance with various aggregate options.
Illustration courtesy of National Terrazzo & Mosaic Association
Rustic cement terrazzo, with its non-slip, textured surface, is ideal for exterior use, offering versatile design options and weather resistance.
COOK COUNTY HOSPITAL: 100-YEAR-OLD CEMENT TERRAZZO TILE RESTORED, MATCHED WITH POURED EPOXY
Photo courtesy of Fotografix Viken Djarferian
In Chicago's Cook County Hospital, original cement terrazzo tiles were restored, and epoxy terrazzo was poured with joints cut to replicate tiles.
Restoration began in 2018 to bring the Cook County Hospital back to life. The Chicago landmark was completed in 1916 as a 3,000-bed hospital. The building eventually fell into deterioration, officially closing in 2002. It sat vacant until 2018, when developers converted the structure into a 210-room Hyatt Hotel, with medical office space, restaurants, and other amenities, including a museum to honor the hospital’s legacy. “During our first walk-through, we were overwhelmed with the condition of the building, not to mention the damages to the floor and base,” said Steve Menconi of Menconi Terrazzo of Bensenville, IL. To celebrate and leverage the old-world beauty that remained, the old cement terrazzo tiles were restored to their original brilliance, with classic terrazzo details elegantly preserved. The terrazzo tile installations on eight floors, each with its own set of colors and design dynamics, were painstakingly replicated with 15 hand-selected colors. Notably, no divider strips were used in the original installation or the restoration. Where extensive repairs were required, epoxy terrazzo was poured in place to match the original design. After the floor was ground and grouted, the contractor cut simulated grout joints with a thin diamond saw blade to replicate the precast terrazzo tiles.
The classic terrazzo design details, including the accent borders lining the hallways, were elegantly preserved. Some 15,000 square feet of flooring and 4,500 linear feet of new cove base were installed with the specified matte finish. “This elegant lady, who had clearly been headed for a date with a wrecking ball, slowly came to a glorious rebirth under an extensive restoration and has become the jewel of Chicago’s west side,” remarked Mr. Menconi. The transformation of the Cook County Hospital was part of the Harrison Square community development plan to bring revitalized residential, retail, medical, and office spaces to the area. Designed by Chicago firms Skidmore, Owings & Merrill and Koo Architecture, the LEED-certified redevelopment project won the 2020 Landmark Illinois Richard H. Driehaus Foundation Preservation Award for Adaptive Use, and the terrazzo installation won an Honor Award from the National Terrazzo & Mosaic Association the same year.
C. Substrate Preparation
As a poured-in-place material, terrazzo requires a flat substrate to achieve a smooth finish and a durable bond. Proper substrate preparation is vital for a terrazzo floor’s performance, longevity, and appearance. NTMA specifications require that subfloors meet a tolerance of 1/4 inch in a ten-foot span to ensure a flat finish.
Architects and general contractors can ensure a successful installation by working with an NTMA terrazzo contractor, prioritizing flatness over levelness, choosing suitable fill materials, and following best practices. A blend of epoxy and sand is commonly used as fill under an epoxy installation. Many self-leveling products are not compatible with terrazzo; their tensile strength is inadequate for the task. For example, gypsum-based floor materials can lack structural strength and disintegrate with the vibration from grinding terrazzo. Adhering to NTMA guidelines and maintaining clear communication among all parties will result in durable and beautiful terrazzo floors.
Architects and general contractors need to:
- Understand the specific requirements for substrate preparation.
- Be aware of the cost implications and potential issues of different fill materials.
- Collaborate closely with terrazzo contractors to determine critical flatness areas and where levelness can be compromised to save money without risking system malfunction.
- Ensure all parties agree on the substrate preparation method and material choices.
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