How Terrazzo Flooring Functions

How often do you stop to consider the floors beneath your feet? I don't think I had ever heard the term "terrazzo" used for a floor until I visited the "Fabulous" Fox Theatre in Atlanta, Georgia. Built in 1929, the Fox features a Moorish-inspired design and showcases stunning terrazzo flooring.

The word "terrazzo" comes from the Italian term for "terrace," but it also refers to both a material and a method for crafting floors, walls, countertops, benches, and more. Terrazzo can range from simple to highly detailed. At first glance, it might be mistaken for a mosaic, though there's a key difference: mosaic pieces are typically cubic (known as tesserae) and custom-cut for their purpose, whereas terrazzo features chips in varying shapes and sizes, set into a bed of dyed concrete, and then polished to a gleaming finish. These chips can be made of glass, marble, granite, stone, or even mirrored materials. While terrazzo can sometimes be a solid color, it can also incorporate a variety of hues. Whether functional or decorative, terrazzo can be as intricate and beautiful as a mosaic.

Similar floors have been discovered in Western Asia, dating back thousands of years. However, it was in the 15th century that Italian mosaic artisans are credited with creating terrazzo. Legend has it that they took leftover fragments from their projects and used them to decorate their own floors. Terrazzo is known for its remarkable durability, ease of maintenance, and resistance to absorbing bacteria or water. This makes it a popular choice for high-traffic environments such as airports, office buildings, and hospitals. Terrazzo is also growing in popularity for residential use, with some varieties being considered "green" because they can be made with recycled glass or other materials, and they do not release harmful toxins.

Personally, I'd love to have terrazzo flooring in my home. But which variety would I choose? There are three main types of terrazzo flooring, starting with the classic, traditional version, also known as cementitious terrazzo.

Traditional Terrazzo

This type of terrazzo is essentially what the Venetians used centuries ago, albeit with some updates. It was cost-effective for them because it repurposed leftover materials, clay, and even goat's milk as a sealant. Naturally, it demanded many hours of labor, as workers manually polished what was initially a rough surface into something smooth and comfortable for walking. This labor-intensive process is part of what makes traditional terrazzo so costly today—the need for skilled labor and the time it takes to complete.

Traditional terrazzo (also known as cementitious terrazzo) is quite heavy and requires a thick cement base to begin with. There are different variations, but the National Terrazzo & Mosaic Association claims that sand-cushion is the best. On top of the cement slab, a moisture barrier membrane is laid, followed by a layer of sand. Metal or plastic dividers are added to create color variations in the terrazzo and allow space for the cement to expand and contract, preventing cracking. Then comes the terrazzo 'topping'—a blend of cement and aggregates like marble, granite, and others. In total, it creates a floor about three inches thick and weighing roughly 25 pounds per square foot. The cement also takes a long time to cure, or dry.

So, why choose such a heavy material? It’s versatile enough to be installed both indoors and outdoors and typically remains level once in place. The material breathes, helping to reduce concerns about moisture, which is particularly useful when installing outdoors or in a basement. It can handle large chips, although it has limitations in the types of aggregate used—things like glass aren’t suitable because it’s non-porous and can’t bond with the concrete. Additionally, color options are limited, as the cement is dyed, and this kind of terrazzo works best with simpler designs like squares due to how the cement cures.

If traditional terrazzo seems too cumbersome and complex for your tastes, next, we’ll explore a more middle-ground option among terrazzo types.

Polyacrylate Terrazzo

This version of terrazzo offers several advantages over the traditional kind. The chips aren't simply embedded in thick cement; they are set in a mixture that combines cement and latex. The latex reinforces the concrete, enabling the terrazzo topping to be applied as thin as three-eighths of an inch. Instead of floating over the cement sub-floor on a sand cushion, it's directly bonded to the concrete layer beneath. Polyacrylate terrazzo systems cure much faster than their traditional counterparts—sometimes being installed in a single day—especially because they are usually attached to an existing concrete slab.

Thanks to the fast curing time, polyacrylate terrazzo requires less labor and fewer materials, making it more affordable. If you’re considering terrazzo for your home, it could be a great choice if you already have a level slab. Leveling is crucial, as polyacrylate terrazzo can’t be installed on uneven floors. The concrete slab must have joints placed at specific intervals (depending on the floor size), and dividers must be used over these joints. Additional dividers can create more color variation, but only dividers placed over joints will help prevent cracking. This is because the terrazzo topping layer is so thin—about four and a half pounds per square foot.

Polyacrylate terrazzo is breathable, so it can be installed outdoors too. Unlike cement-based terrazzo, certain polyacrylate formulations allow the inclusion of glass and mirrored chips—recycled glass, too. The aggregate can vary in size, and polyacrylate can be dyed to match virtually any color, even in more vibrant shades than traditional terrazzo. It’s commonly used on walls and other surfaces due to its thinness and quick curing. If I could, I’d choose polyacrylate terrazzo for my home. Plus, it doesn’t require any harsh-smelling solvents like some epoxy terrazzo types. But those also have their own benefits. Keep reading to see why it's the most popular terrazzo choice today.

Epoxy Terrazzo

If traditional cementitious terrazzo is perfect for basements and outdoor spaces, and polyacrylate terrazzo offers a broad range of colors, what’s the deal with the third option? Once upon a time, traditional terrazzo was the only game in town. But in the 1970s, epoxy, or resin-based, terrazzo came onto the scene and transformed the terrazzo flooring industry, making it far more affordable. According to the National Terrazzo & Mosaic Association, epoxy now commands over 70 percent of the terrazzo market. It’s the most versatile, durable, and resistant to scratches, fading, cracking, or staining.

Epoxy terrazzo flooring can be as thin as a quarter inch and can be applied over a prepared concrete slab or even plywood sub-flooring, depending on the thickness required. It’s used in multi-story buildings because of its light weight—only about three to four pounds per square foot. Epoxy terrazzo comes in any color you desire and is perfect for creating intricate, multi-colored designs. It can be installed with very few dividers, especially when laid over plywood. Plus, it’s impervious to moisture, meaning it won’t support mold, mildew, or bacteria growth.

While its non-breathable nature makes epoxy terrazzo ideal for sanitary settings, it also means that moisture can get trapped between the concrete slab and the terrazzo topping. Some contractors install a vapor barrier to combat this, but it can cause the topping to loosen over time. Epoxy terrazzo also isn’t suitable for outdoor installation—its lack of breathability and the fact that epoxy can fade in sunlight make it impractical for exterior use. Another drawback is the solvent used during installation and cleanup with some epoxy terrazzo types. Solvent-free versions exist, but they are the only ones that can be used in places with shared ventilation systems, such as hospitals. Otherwise, the fumes are too overpowering.

As you can see, each terrazzo type has its strengths and weaknesses, depending on your needs. They tend to be more expensive than many other flooring options. Next, we’ll dive into the detailed process of installing terrazzo.

Terrazzo Installation: The Foundation

Whichever type of terrazzo you decide on, the installation process will be more involved than laying carpet or hardwood. While some flooring options lend themselves to weekend DIY projects, terrazzo is not one of them. Unless you happen to be a professional mason. If you want terrazzo in an existing building, you’ll need to hire contractors who specialize in this type of flooring. Each contractor has their own method, and though we’ve covered the three main terrazzo types, there are many variations, with each contractor having their own preferences. Let’s imagine you’re ready for terrazzo installation.

First, your contractor will evaluate the condition of your current sub-flooring. If you’re opting for traditional terrazzo, a thick concrete base is necessary, which might require excavating beneath your house to accommodate the sand layer beneath the cement base and ensure it aligns with your current floor level. This can be time-consuming and costly, but if you're installing it outdoors, it may not be as challenging. If you have a concrete slab already and are getting polyacrylate or epoxy terrazzo, your contractor will just need to verify it is sound and level. They’ll also locate any existing joints in the concrete. In some cases, epoxy terrazzo can be installed on plywood sub-flooring—something many of us have in our homes.

Let’s go with the concrete slab scenario. The workers will clean it, repair any damage, and prepare it for the specific terrazzo installation you’ve chosen. This preparation process is called creating the CSP (concrete surface profile). A thicker terrazzo type, like the traditional variety, requires a rougher surface, while thinner systems like epoxy can be laid on a relatively smooth base. In some cases, a special membrane may be applied over the cement to help prevent cracking, or in the case of epoxy terrazzo, to serve as a moisture barrier.

For traditional terrazzo, the process starts with a sand layer, followed by cement, and then the design is added on top. In contrast, with polyacrylate and epoxy terrazzo, the design is applied directly onto the surface. Planning is key here and the approach varies based on the terrazzo type. Some contractors even print out the design on paper and position it, full-size, on the floor. How intricate would you like your design to be? To separate color transitions, dividing strips are used, which can be made from materials like plastic, copper, zinc, or brass. These strips not only create the separation but can also form part of the design itself and come in varying thicknesses. For highly detailed patterns, designs may be pre-laid on wire mesh panels, or templates might be cut using water jets, while other parts are shaped on-site. Contractors will solder joints and attach the strips using glue or other methods. The final step is nearly here...

Terrazzo Installation: The Decorative Phase

And now for the fun part! The cement, cement matrix, or epoxy is prepared on-site, with colors mixed directly into the blend. Then, the aggregate—whether glass, marble, or granite chips—is added. If you're using a variety of colors, each one requires a separate mix. Epoxy hardens quickly, meaning it’s applied in smaller sections. The mixture is then evenly spread between the divider strips with trowels, or poured if the aggregate is finer. Afterward, the curing process begins, which could take anywhere from a few hours to several days, depending on the type of terrazzo.

Once the terrazzo has cured, you may be surprised at how rough and rustic it appears. In fact, it may resemble lumpy concrete. While this look may suit some outdoor spaces, most people prefer a more refined finish inside their homes or offices. That's where grinding comes into play. A large grinding machine, equipped with diamond or carborundum (silicon carbide) discs, smooths out the surface and reveals the beautiful chips. Small air pockets that formed during the application are filled in with grout. Finally, a sealer is applied to protect the terrazzo from staining or moisture damage.

The final step is polishing and waxing—this is when terrazzo truly shines. Now, was that initial cost worth it? You may wonder. According to a cost estimator from the National Terrazzo and Mosaic Association, the price in my area ranges between $10 and $16 per square foot. However, terrazzo offers what professionals call a 'superior life cycle cost benefit.' While the upfront cost can be steep, you won’t have to replace or repair it for at least 40 years, unlike other flooring options like carpet or tile. So go ahead and enjoy it, or, if you're like me, simply appreciate its beauty and durability with every step you take across it.