VENETIAN TERRAZZO

Similar to Palladiana, Venetian terrazzo is crafted using premium materials such as marble, granite, and other natural stone. “Venetian terrazzo offers a unique combination of luxury and finesse. Experienced artisans utilize their specialized skill set to craft intricate patterns and designs that are unique to each piece, a process that has been perfected through generations of practice,” said Biswas.

Offering some historical perspective, Hedges explained that craftsmen from Italy’s northeast Friuli region would gather various colored pebbles from nearby rivers and incorporate them into the first “battuto” (meaning “beaten down”) mixes. These finishes came to be highly sought after in Venice, France, and eventually all of Europe and the U.S. “Terrazzo became known as one of the most elite and desired trades in the construction industry due to the meticulous skill and unparalleled quality of their ‘battuto venezia.’ Venetian aggregates, which are larger in diameter than the standard size, offer a refreshing take on an antique style of flooring that works well in today’s interiors, be it ec-lectic, minimalist, rustic, or contemporary,” relates Hedges. “Venetian terrazzo can offer a more monolithic appearance to a floor with fewer joints and seams than stone or tile, and can also produce complex patterns,” adds Michiels. “You can get pretty specific with colors, and use the aggregate to create a subtle effect or one that is more expressive.”

The slab may need to be recessed to allow for the larger Venetian aggregate. Typically, with aggregates between 3/8-inch and 7/8-inch in diameter, the terrazzo must be poured at 5/8-inch or more to accommodate the larger stone. It’s added to an epoxy or cement mix and troweled on the prepared substrate. It’s also possible to sprinkle the aggregate on the troweled mix and then roll out. Once the mix cures, it is ground and polished.

EPOXY VS. SAND-CUSHION CEMENT

As the matrix for Palladiana or Venetian terrazzo, sand-cushion cement is the traditional choice while epoxy is a popular alternative offering a number of benefits. Both matrixes are typically devoid of VOCs and are often GREENGUARD certified, and offer a high level of compressive tensile and flexural strength. “Epoxy is a powerful adhesive that provides an impenetrable bond between the substrate and terrazzo mixture, generating a lasting and secure surface. Furthermore, it is impervious to stains, chemicals, and water, rendering it a great option for highly trafficked spaces,” explains Biswas.

Epoxy’s physical properties are at least six times greater than cement terrazzo, which gives it better crack resistance. In addition, it is available in more colors and installs faster. Another advantage of epoxy is that it has no shrinkage therefore the demand for divider strips is less than a cement system. Because epoxy terrazzo requires much less depth, it is ideal for applications where the floor finish weight or depth is restricted, particularly in a renovation where a thinner floor finish may have been previously accommodated. It is also possible to apply the epoxy directly to an existing concrete slab in many cases.

The thicker cement system offers the advantages of greater tolerance for an imperfect slab. “The cementitious and layered system is about 3 inches thick in total. It is more forgiving of uneven, imperfect floors because of the thick underbed below what is still a relatively thin layer of terrazzo,” relates Michiels. “I actually think it has a great aesthetic quality as well as the cementitious matrix has a warmth and authenticity to it that is quite nice.”

While a designer might be aware of the pluses and minuses of epoxy vs. cement for a given application, additional intricacies may arise that only an experienced terrazzo contractor would be able to uncover. “The advantages or disadvantages to both cement and epoxy terrazzo will make one system good for a project. However, this changes with the details and design of each project, which is why it is so important to bring in an NTMA contractor early in the design process,” advises Menconi. For example, if sand-cushion terrazzo is used with a thicker assembly, this greater depth must be accommodated by the structure, meaning that slabs must be lowered or otherwise depressed, requiring more planning and coordination during the design phase.

Additionally, sand-cushion terrazzo is isolated from the concrete slab by a plastic membrane to aid in the suppression of cracking. Because cement is a breathable material, it can be installed in areas where a vapor drive is suspected, such as a slab-on-grade. The plastic membrane can be installed over areas where cracking in the concrete is a concern, says NTMA Technical Director Gary French.

Divider strips must be placed at a much greater frequency in sand-cushion than in epoxy, typically every 4 feet in each direction to control shrinkage in the finish panels. However, the thinner epoxy system means that less consideration of its depth and weight is required.

An epoxy system is suitable for retrofit application on existing slab on grade where the presence or integrity of a vapor barrier below the slab is suspect, with a moisture control system, he explains. Because epoxy is sensitive to vapor drive, a moisture control system typically must be applied.

A good example of both sand-cushion terrazzo and epoxy terrazzo, selected in response to differing design and technical requirements, can be seen in Cooper Robertson’s renovation and expansion of the Museum at Gateway Arch National Park in St. Louis. For this 2019 NTMA Honor Award project, sand-cushion terrazzo was used for the new public exhibition spaces on the expansion’s lowest level and to replace a terrazzo installation in the existing museum, which was possible because a sufficient depth was available in the floor. “Sand-cushion terrazzo was primarily chosen for this application due to its capacity to accommodate larger aggregate, which was selected to match the grand scale of the public spaces it was installed in,” explains Barwick.

In addition to the concrete installations, Missouri Terrazzo installed epoxy terrazzo at elevated slabs at smaller-scaled spaces within the building on account of its thinner, lightweight assembly. “Epoxy terrazzo’s high strength and color range were particularly capitalized upon in the installation of an expansive map of North America that traced the path of westward expansion in the U.S. This permanent installation was comprised entirely of epoxy terrazzo in varying colors to represent land masses, rivers, lakes, trails, and landmarks,” Barwick adds.