What is Terrazzo?
- Terrazzo is a trending building material today, seen in places like airports, schools, hospitals, hotels and even in people’s home.
- We define terrazzo as a composite material, either poured in place or prefabricated for precast terrazzo, which is then used for flooring base, stair treads, walls, and countertops.
Components of Terrazzo:
|AGGREGATE + MATRIX|
Which is combined in either a cement or epoxy matrix as the as the binder.
Purpose of Divider Strips:
When installing terrazzo metal divider strips are also used. Divider strips are used to:
- Divide sections of floor
- Make color transitions
- Design detailed logos and decorative pieces
- Allow for movement and crack mitigation.
Aluminum is the most common used to divide strips. However, zinc, brass or plastic are considered as well.
2.0 History of Terrazzo:
Terrazzo can be found at historical landmarks around the world. Some locations include the Hollywood walk of fame. Terrazzo origins is given to the Italians. Terrazzo is an Italian word meaning “Terrace”
In the 15th century Phoenicians used scrapped marble fragments from high-end projects and place them in clay mortar for their own terraces. Archeologists have even found evidence of terrazzo and ancient ruins in Turkey dated back well over 10,000 years ago.
Terrazzo is similar to the technique “Seminato” where workers would toss large marble chips into wet cement to be ground and polished. Terrazzo began making its way to America around 20th century. The 1920s saw the rise of terrazzo in America, craftsmen were recycled aggregate to create Italian style terrazzo floors for lobbies of hotels and apartments. It was during this time electric grinders were invented which is also contributed to the growth of terrazzo, these machines created a finer finish with greater speed and accuracy. Over time terrazzo began to evolve.
Epoxy Terrazzo was introduced by the 1970s, offering an alternative to traditional terrazzo systems, and is widely used today.
Ways epoxy resins improved terrazzo installations:
- Quicker cure time than cement terrazzo systems
- Less susceptible to cracking
- Greater design flexibility and expanded color options
- Stronger and more durable at 1/4” and 3/8” thicknesses
(Even though it’s a thinner its generally stronger and more durable and less prone to cracking than cementitious systems as well. They can last up to 75 years on average. With epoxy terrazzo there is also a greater design opportunity in terms of color selections and aggregates used. There is endless amount of epoxy colors and these colors remain permanent throughout the materials life cycle. In addition to traditional choices in aggregates such as marble and granite, epoxy also made weight for use of post-consumer recycled glass, mirror, plastics, porcelain and concrete.
Terrazzo is relevant once again today for its sustainable features with low amounts of volatile organic compounds and is a good source of recycled content. As a result, terrazzo has to become an excellent choice for architects.
- Sustainable building material – recycled content and regional sourced materials help architects with LEED (Leadership in Energy and Environmental Design) credits.
- Diverse ways to use terrazzo
- Terrazzo Systems
- Cement terrazzo
- Epoxy terrazzo
Common cement systems include
- Sand Cushion
Main feature of Monolithic Terrazzo:
- 1/2″ Terrazzo topping = 1.27cm
- 5-7 lbs
- Applied directly over concrete subfloor
Monolithic terrazzo is a system where a half-inch terrazzo toping is bonded directly to a new or existing slab. Panels are then poured withing the directly bonded metal L angled divider strips.
Main features of Sand Cushion Terrazzo:
- Wire Mesh
- 5” (6 cm) to 3” (7cm) including 0.5” (1cm) terrazzo toping
- 25-30 lbs.
- Isolation membrane or sand dusting
Sand Cushion terrazzo is a system where terrazzo is poured over a wire reinforced two and a half inches to three-inch mud bed of sand and cement mixture while the mud bed is still soft, standard metal divider strips are partially embedded in the mud bed wherever there is to be a joint or a color change.
Underneath the mud bed is an isolation sheet on top of a 1/16-inch sand dustion creating a floating flow which allows for horizontal movement in the building thus practically eliminating the possibility for cracking.
Main features of Rustic Terrazzo:
- Recommended for exterior application
- Bonded or monolithic
- Slip resistant textured finish
Thin- set terrazzo systems include:
- Epoxy Terrazzo
- Polyacrylate terrazzo
Main features of Polyacrylate Terrazzo:
- Cement system
- Thin-set at 3/8” = 0.9525cm
- Allows for vapor transmissions
Polyacrylate is a cement modified acrylic creating higher compressive strength and higher impact resistance to cement it also allows for vapor transmissions.
Main features of Epoxy Terrazzo:
- Two components:
Part A resin & Part B hardener
- Thin set ¼” (0.6cm) or 3/8” (1cm
- 3-4 lbs
- Vapor barrier required
Epoxy terrazzo system is similar to a monolithic terrazzo system but installed at a minimum of 1cm thickness. Set epoxy is a two-component resin which bonds directly to the concrete slab. A moisture mitigation system of or crack suppression membrane may be required. A vapor barrier is required below the slab for all slab on grade applications, this system is installed at 0.6cm to 1cm finish.
Differences between Cement and Epoxy Terrazzo
- Color is a main advantage for epoxy terrazzo
- Cement terrazzo is best suited for Pastel and darker colors
- Easier to patch an epoxy terrazzo floor, as colors can be easily matched. Unlike a cement.
Aggregate options available for epoxy Terrazzo:
Other characteristics of epoxy terrazzo includes:
- Lighter weight
- High compressive and tensile strength
- Faster installation
- Impermeable finish (No water or gases passes through)
- Less susceptible to cracking during lifecycle
There are a few challenges for epoxy Terrazzo:
- Epoxy terrazzo does not react well with heat and ultraviolet rays, therefore, is a primarily an indoor application. For exterior application, its recommended to use a rustic system.
- Terrazzo toppings may not be vapor permeable, therefore, a moisture mitigation system is recommended to preventing moisture from passing through the terrazzo’s surface.
Methods of installing epoxy and cement terrazzo are quite different
- One of the first steps of an epoxy terrazzo installation is checking for moisture levels. Moisture level must be in tolerance, and moisture mitigation systems may be required.
- Next step is surface preparation. Installers will create a strong bond between the substrate and the terrazzo.
During the surface preparation stage, installers will check the crack details and floor level tolerance. Flexible epoxy can fill in cracks as shown, which help assist in prevention of substrate cracks transmitting to the terrazzo floor during the entire floor lifecycle.
- Installers start placing divider strips in designated locations to form the design layout. Divider strips indicate change in color or can create complex patterns.
- Once the layout is finished, installers can begin mixing components for either epoxy or concrete terrazzo.
Mix Ratio 2:1 of marble aggregates and either grey or white cement. Iron oxide added for color.
- Installers use hand trowel to spread the terrazzo evenly across the surface at the desired thickness.
- Aggregate is seeded across the floor and rolled across in alternating directions, this allows the aggregate to become embedded into the terrazzo while moving excess cement water to the top to be removed from the floor. This process is repeated several times with different graded roller and allowed to cure for SEVERAL DAYS.
Note: Cement terrazzo installation will take several days to cure. Once fully cured, installers can begin grinding.
Installing Epoxy terrazzo is different than cement terrazzo.
- Faster Installation
- Different mix ratio
- Less labor intensive
Mix Ratio 5:1 meaning 5 gallons of a part A resin base color and 1 gallon of a part B hardener. Both the part A and part B are mixed together with filler powder and a minimum of 180 pounds aggregates added to the mix. This batch is then poured over the surface and areas that specify a color. Installers continue to spread the batch evenly across the space at the required height using a hand towel or power trowel.
Note: 1gal = 3.785kg wt, 1 pound = 0.453kg.
Epoxy terrazzo can cure typically in 24 hours (Cement terrazzo takes typically 4 to 5 times longer to cure the epoxy terrazzo)
- Grinding for both cementitious terrazzo and epoxy terrazzo relatively are the same procedure with exception for the initial rough grinding. Rough grinding is different for both systems.
Epoxy – Dry, leaving dust to be vacuumed
Cement – Wet, leaving behind slurry
Grinding concludes when the divider strips and aggregates are exposed on to the floor. After this stage, its time for grouting.
- Prior to grouting:
- Installers will clean the terrazzo floor with clean water and an auto scrubber.
- Allow the floor to completely dry.
Grouting is the process of covering any pinholes or void left over after the grinding process. Installers will apply a small amount of epoxy matching the floor color covering up these pinholes.
- The procedure for polishing is performed similar to the grinding stages. However, polishing is done wet for both systems. Once completed, the terrazzo floor is left to be completely dry which is then to be applied with a minimum of two coats of sealer.