Cement vs epoxy terrazzo: what your floor is made of

Terrazzo is two materials: a matrix that binds and an aggregate that shows. The NTMA’s restoration specification puts it in one line: terrazzo floors “are either a cement or epoxy matrix (binder) with a variety of aggregates.” In a Hillsborough County house built between the mid-1950s and 1970, the answer is nearly always the same, a Portland cement matrix with marble chips, and knowing that decides how the floor is ground, patched and sealed.

There are no brand names on a terrazzo floor. The things that matter are the system, the matrix and the chips. This page explains each in plain terms.

The systems, by thickness

The NTMA’s systems reference guide defines the common ones. Two are the ones you might find in a Tampa house; the rest are mostly commercial.

Monolithic is the one that matters most here. The NTMA describes it as a cement matrix system that bonds directly to the concrete slab and is “dependent on quality of the concrete slab for flatness and crack prevention,” with a half-inch nominal topping. That is why house terrazzo cracks where the slab cracks, and why cracks often show beside a strip that sits over a slab joint. See cracks along divider strips.

Cement matrix

Portland cement, white or gray, often pigmented. The NTMA notes that “cement, both white and gray, may not be uniform in color,” which is part of why two rooms of the same 1960 house can read slightly differently. The cement is the porous part of the floor. The NTMA’s care guide says the Portland cement binder is the part of a cement terrazzo floor that benefits most from a sealer. It is also the part that soaks up pet urine and rust, and the part acids attack.

On a restoration, grinding opens fine pinholes in a cement matrix. They are filled with a grout matched to the matrix before the fine passes; the NTMA’s restoration specification has the grout cure at least 12 hours. That step is the difference between a floor that polishes to a clean, even surface and one that looks speckled with tiny holes.

Epoxy matrix

Resin instead of cement. The NTMA’s care guide describes the epoxy binder as fundamentally non-porous, so a sealer mainly protects the aggregate and the look of the surface. Epoxy allows bright, even colors and glass, mirror or other aggregates, and the NTMA’s systems guide credits it with the greatest tensile, compressive and flexural strength of any system. It is not what you expect to find in a 1950s or 1960s Tampa house. If you have bright, glassy terrazzo in a house, it is either a later installation or a commercial-style job.

The chips

The NTMA grades terrazzo aggregate by number. A #0 chip passes a 1/8 inch screen, a #1 passes 1/4 inch, a #2 passes 3/8 inch, and so on up. Cement toppings customarily use No. 1 and No. 2 chips. In practice:

• Small-chip floors close up quickly under the resin-bond grits and patch easily.
• Larger-chip floors take more passes to bring chip and matrix to the same polish, which pushes a job toward the top of the $5 to $9 per square foot range.
• Color comes from the marble itself, and matching it for a patch depends on finding chips of the same stone. The NTMA warns that matching existing aggregates may not be exact because they are mined products that may alter over time.

A short history of the cement floor

The NTMA’s own history traces terrazzo in the United States to 1890, when Italian craftsmen laid it in the Vanderbilt residence on Fifth Avenue in New York. Two inventions of the 1920s made it a mainstream floor: the electric grinder, invented in 1924, and the availability of brass divider strips, which made patterns practical. By the time Florida’s postwar building boom arrived, cement terrazzo ground on site was an established way to finish a slab, which is how it ended up in so many concrete block houses. The newer thin-set and epoxy systems came later and are less labor-intensive, the NTMA notes, which is part of why they took over in commercial work.

How the type changes the price

These match our pricing page.

Telling yours apart

Send a close photo of the floor with a coin beside it and one of a divider strip. From those we can usually tell cement from epoxy, the chip size, and whether the strips are brass or zinc. The divider strips page explains the metals, and the restoration page covers the whole job.