Terrazzo’s Comeback–It’s Not Just for Floors

Emerging from its Art Deco and mid-century popularity, new and exciting terrazzo designs have burst onto the scene
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Sponsored by National Terrazzo & Mosaic Association
By Barbara Horwitz-Bennett
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The monolithic Venetian terrazzo serves as the focal point of all interior finishes, and was selected as the common denominator to coordinate the aesthetic of this classically simple, multi-use space. The larger Venetian aggregate and handcrafted, heavy-top divider strip beautifully complement the scale and elegance of the site. The aggregates and divider strips were poured-in-place and required a high level or craftsmanship to install the tread and risers, and grind the large chips on the edge of the ramps to achieve the perfect flatness of vertical surfaces and consistent aggregate density on all surfaces.

“With the larger aggregate, the terrazzo had to be poured thicker than usual, and there was difficulty working the large aggregate into the mix at the stairs and ramp. The installation and grinding were both more tedious than with epoxy terrazzo,” reports Maraldo. In order to maintain a high chip density and consistency, the crew tried to incorporate as much aggregate into the mix as possible, while seeding any areas that appeared to lack the required density. To match the ramp and its wall with the floor, this involved constantly checking to ensure that the proper tolerances were being maintained. The Bank of America Tower also bears the distinction of being the first LEED v4 Platinum Core & Shell certified project in the U.S.

Another Houston project earned the 2022 Job of the Year award from the National Terrazzo & Mosaic Association – the city’s Museum of Fine Arts, featuring extensive sand-cushion Venetian terrazzo flooring, staircases, raised seating, coves, and a plinth.Paying homage to the still beautiful and functioning green terrazzo floor installed by the contractor’s grandfather some 65 years ago, the project incorporates a transitional lobby space replicating the original terrazzo.

Photo courtesy of Jaime Leigh Sonnier-Casa de Camera

At Houston’s Museum of Fine Arts, terrazzo is significantly featured in flooring, staircases, raised seating, coves, and a plinth.

In the Kinder Building, which houses international collections of modern and contemporary art, more than 48,000 square feet of sand-cushion Venetian terrazzo with larger (sizes 4-7) chips were installed.

Complementing the gallery’s stairways and glass, Steven Holl Architects specified a blue-gray color for the terrazzo. Since a level, flat floor was critical for the art display, and to accommodate air vents located on the floor flush with the terrazzo, a high level of craftsmanship was required. All the zinc divider strips were formed by hand onsite and the craftsman delivered consistent color throughout all the spaces.

From the museum’s lower level, a cementitious terrazzo raised seating platform anchors the 61 steps leading to the intermediate level and the main floor with a rear cove, requiring precise installation. The staircase’s three landings were poured in place. The coved base was precast, installed with a zinc toe strip, and polished top with a 1/8-inch bevel. The next poured-in-place suspended staircase was designed with 41 steps of varying lengths and widths, set on a plinth, and serves as an architectural element for the space.

A tunnel connecting the Kinder Building to another part of the complex incorporates 4,000 square feet of white sand-cushion terrazzo where smaller size-1 and size-2 chips were installed.

Terrazzo also played a key role in the expansion and upgrade of the Denver Art Museum, most notably the creation of a seamless, elliptical staircase. In celebrating the 50th anniversary of the museum’s Martin Building, Fentress Architects modeled the new staircase after famous Italian architect Gio Ponti’s original poured-in-place cement terrazzo staircases. Now functioning as the visual and logistical center of the complex, the epoxy thin-set terrazzo was designed as a two-story central spiraling balustrade which unfurls like a ribbon. Appearing as a monolithic whole, the treads and risers are precast terrazzo; the landings are poured-in-place to eliminate joints; and the guard walls are poured-in-place, hand-ground, and polished. During construction, terrazzo artisans mocked up the section of the stair with the tightest curve to demonstrate the handwork and allow for refinements to the design. Each precast tread was templated prior to the installation of the walls, and the guardrails were installed to align perfectly with a 2-inch stainless-steel reveal.

Photo courtesy of David Laudadio

At the Denver Art Museum, an upgrade and expansion of the Martin Building incorporated a spilling terrazzo staircase modeled after the famous Italian architect Gio Ponti’s original poured-in-place cement terrazzo staircases in the building.

The original 50-year-old staircases in the Martin Building were also fully restored through regrinding, grouting, patching, and polishing to like-new condition. In addition, terrazzo was installed in each of the building’s seven lobby floors, and numerous terrazzo window sills were created along with a top-set base.

Another heavily trafficked area benefitting from terrazzo’s durability is Chicago’s Midway International Airport, which recently added three new bridges. Architect Muller & Muller specified 95,000 square feet of terrazzo flooring and 20 4-foot-tall, wrapped columns, with an integrated cover base perfectly clad to the wood and steel structures.

Photo courtesy of FotoGrafix

Three new bridges at Chicago’s Midway International Airport feature expanses of terrazzo flooring, columns, and cove bases.

“Terrazzo column bases meet a high design standard while still being a cost-effective solution for high-trafficked areas, specifically in an airport where column bases in queuing areas are continuously subject to abuse from luggage, carts, and even vehicles,” explains Ed Frankowski, AIA, LEED AP, Muller & Muller, Chicago. Sharing some details on the installation’s predominant challenge, Menconi Terrazzo’s Menconi says the column was carved out of a random piece of stone, yet his team was tasked with creating a solid stone look. “We also had to create a surface that is flush with the rest of the column, and provide the same dimensions at all areas.” The team’s hard work paid off, as the polished floors flow seamlessly into the coves at the columns.

Showcasing Vertical Terrazzo In Schools

When Eureka High School in Eureka, Mo., added a new STEM addition, the design included a patterned epoxy terrazzo floor with short walls, a 20-foot-long tread and risers, and a handicapped-accessible ramp. The classic terrazzo was crafted in four muted tones with glass and marble aggregate and aluminum divider strips, and showcases the Wildcat mascot in school colors.

Photo courtesy of Viken Djaferian; FotoGrafix

A patterned epoxy terrazzo floor with short walls, 20-foot-long tread and risers, and a handicapped-accessible ramp lend durability and aesthetics to Eureka High School’s new STEM addition in Eureka, Mo.

Relating how Missouri Terrazzo installed the terrazzo, Rickman explains that the ramp, short walls, tread, and risers where formed with concrete along with the concrete floor pour. “We infilled all the areas with a sand and cement mixture to make sure when the terrazzo was installed it would be perfectly straight and flat.” The infill typically ran from 1/16 inch to ¼ inch, depending on the existing concrete, and the terrazzo in these areas was normally 3/8-inch thick. In addition, a cove was installed at the base of the step and riser. “After the terrazzo installation, the crew made sure to grind, grout, polish, and seal the terrazzo while maintaining the flatness of the install. The ramp, stairs, and stringers were also carefully installed and ground to be as flat as possible. The nosings are ground off with a nosing tool to give it a nice round appearance,” states Rickman.

Missouri Terrazzo was also involved with the renovation and expansion of Ladue Horton Watkins High School in Ladue. Mo., where the main lobby area is amphitheater-style seating with benches of poured-in-place terrazzo, inlaid maple seats, and precast terrazzo steps. Terrazzo, in a four-color design, continues throughout the new addition in the art room, commons area, hallways, and cafeteria with a 4-inch precast wall base. “This was a very interesting project as the bench seating was poured-in-place terrazzo, while the stairs were precast terrazzo,” relates Rickman.

Photo courtesy of FotoGrafix

At Ladue Horton Watkins High School in Ladue. Mo., amphitheater-style seating with benches of poured-in-place terrazzo, inlaid maple seats, and precast terrazzo steps are featured in a new renovation and expansion.

Another challenge was making sure the benches and stairs met at the desired height and locations. With the precast terrazzo, caulk joints were needed between the pieces, and the joints had to be mimicked in the poured-in-place style to make sure the design met the architect’s requirements for aesthetics. “The most common thickness of the epoxy terrazzo is 3/8 inch, but as a result, the bench seating was left with a 2-inch gap to meet the existing floor. This area was then infilled with an epoxy and sand mixture to make certain that when the terrazzo was installed, it would meet all of the needed heights elevations,” explains Rickman.

In addition, wooden seats were placed within the terrazzo. “Wood grounds were used to mimic the wood seats so the terrazzo could be poured, rough ground, grouted, polished, and sealed to the exact height of the wood. Every aspect of the terrazzo had to be perfect to match adjacent design choices,” he explains.


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Originally published in Architectural Record
Originally published in June 2022