Epoxy Aggregate Systems
for Decorative Toppings

Epoxy-aggregate. A simple descriptive phrase for a category of decorative toppings that is anything but simple. As floor systems go, they offer a variety of aesthetically appealing and durable surfaces that are hard to beat. If you’ve not worked with these products before, this mini-tour may pique your interest.

Generally, epoxy-aggregate systems fall into two broad categories: porous and nonporous — also called “open” and “closed” systems. The porous systems use epoxy-pebble mortar. The nonporous systems include terrazzo systems, troweled epoxy mortars and broadcast epoxy systems.

As with any decorative topping installation, substrate preparation is the most important step. The substrate should be thoroughly prepared according to specific system directions provided by the manufacturer. Also, expansion joints must be honored and active cracks repaired.

Epoxy-pebble systems
Contractors agree porous epoxy-pebble systems are the least complicated and have many benefits, including hiding puddles and hiding imperfections in the substrate. The variety of pebble sizes and colors available makes these systems aesthetically pleasing, and it is fairly easy to incorporate borders and designs.

Epoxy-pebble systems are most often used for outdoor applications, such as driveways, pool decks, patios and walkways, but are good for indoors, too. Smaller pebble sizes of 1⁄8 to 1⁄4-inch are easier on bare feet. Larger pebble sizes increase the porosity and texture of the surface.

Typically, the epoxy is mixed in a mixer, and then the pebble aggregate is added and mixed until it is well coated and evenly distributed. The mortar is then transferred to the substrate. David McKinnon, vice president of sales for Seamco Labs Inc. in Tampa, Fla., explains the importance of troweling right away: “The excess epoxy runs through the rock into the concrete slab. If you [leave the aggregate in a pile], the epoxy drains through at the pile” and you won’t have good adhesion elsewhere when the material is eventually spread.

McKinnon says you can trowel these systems as thin as 1⁄4-inch to as thick as two to three inches to level a surface, but “the rule of thumb is to install the topping three stones thick to get the proper hiding power and run through on the slab.”

Paul Koury, president of Life Deck Specialty Coatings in San Diego, reports these systems have “quick turn-around — with very little downtime.” To aid troweling, he recommends installers continually wipe their trowel with a solvent to avoid buildup.

The No. 1 negative of these systems is the ambering and degradation of the epoxy in ultraviolet light. Regular maintenance is a must!

Boyan Radovanovic, president of Aggregate Protective Coatings Inc. in Torrance, Calif., explains, “If you don’t maintain it, you’ll have problems. The pebbles delaminate and completely fail from one another.”

How often you reseal depends on the amount of UV exposure, but typically the decorative system should be recoated every 12 to 15 months if it’s in the sun, less frequently if it’s in the shade or indoors.

Terrazzo systems
“Epoxy-terrazzo is the most popular hard-surface flooring today … in commercial settings. It has the lowest life-cycle cost of any hard surface material,” exclaims Robert Cain, president of Key Resin Co. in Cincinnati. You see it frequently in airports, arenas, sports complexes, train stations, universities, schools and hospitals.

Lifetime floors, you might call them. “They are expensive, but extremely long lasting,” Radovanovic says. The expense comes in because “they are labor intensive and require significant downtime in an area.”

The aggregate most frequently used in terrazzo systems is marble, reports Tom Murphy, vice president of marketing for Sherwin-Williams Co.’s General Polymers in Cincinnati. Because the surface of the mortar is always ground to expose the inside of the aggregate, the size of the aggregate is important in achieving certain surface appearances.

The installation process is lengthy. After preparing the substrate and applying a primer, zinc, aluminum or brass strips are placed in the desired pattern. What you have is kind of a paint-by-numbers grid. “You mix [and apply] one color at a time in panels that are not touching. You don’t want color bleed-over from panel to panel,” Murphy explains.

The rough grind is next, exposing the marble and the strips. Air pockets opened in this process are grouted with the same color epoxy used in the mortar mix. Then the surface is polished to take off the excess grout and smooth out other inconsistencies. Murphy points out, “The art in terrazzo installation is in the grinding — that’s what people see.”

Finally, a penetrating sealer closes up the stones and brings out the color.
Basic maintenance is to remove dirt with a dry mop. Terrazzo naturally develops a dull patina, but where a shiny look is desirable, regular application of an acrylic sealer and buffing may be required.