Epoxy Vs. Cementitious Terrazzo
Venetian craftsman of the 15th century created terrazzo flooring using odd-sized marble chips left over from the construction of terraces. Today terrazzo flooring is composed of a mix of aggregates, such as marble, granite, quartz, recycled glass or plastics, embedded in cement or epoxy. It is used in institutions like hospitals and schools and in commercial buildings. Its exterior applications include walkways and patios.
Considerations in choosing a terrazzo system include whether the flooring is for interior or exterior use, or both; whether the system needs to be breathable; whether there are time constraints on installation; and what kinds of aggregates and colors you desire.
The matrix types for terrazzo flooring are Portland cement, polyacrylate and epoxy. Polyacrylate terrazzo is a polymer-modified cement matrix three-eighth inches thick. Epoxy terrazzo, also known as thin-set terrazzo, is a 1/4-inch or 3/8-inch thickness of resin terrazzo.
The sand cushion system, for interior use, is the best cement-based system, according to the National Terrazzo and Mosaic Association, Inc. website. A sand layer or isolation membrane separates terrazzo from substrate with this system. The polyacrylate system is 3/8-inch thick and good for use in areas where moisture vapor transmission do not allow the use of non-breathable floors, such as epoxy terrazzo. It can be used for interior or exterior applications. Epoxy terrazzo resists many chemical spills, making it ideal for labs or hospitals. It is not, however, recommended for exterior use.
Contractors use bonded cement systems where interior or exterior conditions require filling 1 1/4 inch to 1 3/4 inch recessed depth, plus the 1/2 terrazzo topping, according to the National Terrazzo and Mosaic Association website. Another cement system, the monolithic system, is economical and quickly installed for when time and budget are of the essence. However, the system depends on the concrete quality for flatness and crack prevention.
Sand cushion and epoxy systems are both for ground level or multi-story interior use. Sand cushion terrazzo is breathable; it can accommodate substrate defects; and it can accommodate the largest aggregate chip size. However, it requires a minimum two-inch depression for installation and a lengthy cure time. Epoxy terrazzo can be used over a concrete or wood substrate; it has greater design flexibility; and its color range is unlimited and the colors vibrant. However, its thinness means that the substrate must have a high flatness tolerance and its non-breathability means that slab on grade applications require a moisture barrier at additional cost. The epoxy binder is more expensive than the cement binder, but epoxy terrazzo enjoys the cost advantages in installation and maintenance, according to the Master Terrazzo Technologies website.