Construction Methods for Terrazzo Floors

History of Terrazzo

• Terrazzo was discovered in the 15th century by artisans who crafted mosaic tiles. They swept chips from the cut marble tiles onto their terraces as they worked. They eventually set the chips into clay base and began to polish the terrace surface with hand stones to bring out its beauty. Over the centuries, the method of creating terrazzo has been perfected and today professional installers can create stunning designs using precise, time-tested techniques.

Preparing the Slab

• To prepare for the terrazzo workmen cut the concrete slab into a grid to control the expanding and contracting concrete and prevent cracking. Next, they thoroughly clean the slab to prevent any mold or algae from growing on it. They set zinc dividers into the grid-lines and set 2 by 4s around the slab's outside perimeter as a temporary barrier. The last step in preparing the slab is to apply a thin coat of epoxy.

Pouring the Floor

• The terrazzo mixture is dumped from wheelbarrows onto the prepared slab and spread with rakes and shovels. Workers then compress the mixture with a large roller. To ensure the wet terrazzo is fully compacted, workers use floats and trowel the entire surface by hand. They then spread more chips of marble, glass or whatever aggregate they are using over the surface. The surface is smoothed a final time with the roller and allowed to cure over the next two days.

Polishing

• After the terrazzo has cured for two days, workers drag a 500-lb. grinder across the lumpy surface to begin the polishing process. The grinder has 12, 4-inch diameter diamond-grit stones. After several passes the grinder stones are replaced with a finer grit to increase the shine. Once the floor is polished, a thin layer of colored cement is spread over the surface to fill any remaining air bubbles. When the colored cement is set, workers go over the surface a final time with a grinder. At this point, the terrazzo is gleaming and has reached its finished state.