ICS Magazine

Maintaining Terrazzo Flooring

January 13, 2009

Recently I received a call from an individual concerned about her terrazzo lobby. She said that no matter how much they stripped the floor, it retained a blotchy appearance. She was concerned she may have damaged the floor and would not be able to fix it.

On arrival I noticed the floor was in the process of being stripped, and some of the areas did look blotchy. One of the obvious reasons was that not all of the floor finish had been removed in some areas, but there was also an underlying blotchiness that could not be attributed to remaining floor finish.

Terrazzo is a durable floor used in heavy-traffic environments as well as an artistic medium. Terrazzo is a combination of various sized crushed marble or granite chips mixed in a cementitious or resinous binder. The proportions consist of 70 percent marble or granite and 30 percent binder. Traditional terrazzo is generally poured on site in an aluminum or brass framework and then ground, honed or polished using diamond abrasives. In many cases – such as this one – terrazzo is maintained using acrylic polymer floor finishes in the same manner as vinyl composition tile.

Just because terrazzo is durable does not mean it does not succumb to the damaging effects of erosion. The abrasive action of moisture, soil and foot traffic can cause traffic patterns in polished terrazzo. Terrazzo maintained with floor finishes allows the floor finish to erode first before impacting the terrazzo itself. Walk-off matting should be used at all entrances to buildings that have terrazzo to reduce this erosive effect; they will help to capture most or some of the gritty material at the door.

It is a given that not all soil will be stopped or eliminated; some will undoubtedly enter the building and be redistributed throughout the facility. Daily or routine sweeping, dust mopping or vacuuming will reduce the dry particulate soil that gets past the walk-off mats. Soda, fruit juice and coffee spills should be removed as soon as possible to avoid staining natural or untreated terrazzo. Some stains that permeate into the cementitious binder may be removed using a poultice, a combination of cleaning solution and talc used to draw out stains.

Most light, moderate and heavy organic soils can be removed using one of the wet-mopping service procedures. Although a thorough wet mopping should be performed daily in heavy-traffic environments, less frequency is acceptable for areas with light or moderate traffic conditions. Use neutral cleaner (a pH of 7 is absolute neutral) diluted to the manufacturer’s recommendations. Hazing and streaking may occur on highly polished terrazzo due to soiled mops or poor mopping techniques. When cleaning chemicals are applied to the floor, it causes the soil to be suspended in the solution. As the solution dries it carries the soil with it; the last areas to dry will have the most soil residue. A final damp mop of the floor to remove the excess solution will help to reduce this problem.

Periodic scrubbing of the floor will be sufficient to remove embedded or ground-in soil that accumulates on polished terrazzo. For those floors with floor finish applied to them, the scrubbing procedures will remove heavy, embedded and in some cases encapsulated soils in preparation for applications of new floor finish. All-purpose cleaner may be substituted for neutral cleaner to remove these difficult soils. Always use cleaning chemicals in accordance with manufacturer’s recommended dilution ratios, and rinse thoroughly to remove potential alkali residue. When scrubbing a terrazzo floor, use a wet vacuum to remove the contaminated cleaning solution.

Coating maintenance may incorporate the use of high-speed or ultra-high-speed buffing machines to elevate the gloss levels. When these systems are in place, use the appropriate conditioner or restorer chemical designed for the floor-maintenance program.

The restorative procedure will be either diamond-abrasives-and-powder-polish for terrazzo without acrylic polymer floor finishes, or the strip-and-refinish service procedure for terrazo with acrylic polymer floor finishes (as is the case with our case study floor). The definition of a strip is to remove all pre-existing coats of seals and/or finishes, detail edges, corners and baseboards, and then reapply multiple coats of floor finish. High-speed or ultra-high-speed buffing may be performed for those systems after the floor seal/finish has dried.

During the stripping process, one of the objectives is to remove all pre-existing coats of floor seal and/or finish. Before reapplying the floor finish it is essential to inspect the floor to ensure that the floor finish has been removed. If all of the seals and finishes have not been removed, it may result in a blotchy appearance, which brings us back to my customer’s floor.

My customer stripped the floor again and removed all seal and finishes, yet the floor remained blotchy. The answer to this dilemma was in the terrazzo placement. Although terrazzo is 70 percent marble or granite chips in 30 percent cementitious or resinous binder, it is not always distributed evenly. This floor had variations of white chips in a dark-gray cementitious binder.

When looking at the entire floor it looked even, but when you looked at certain areas, they were indeed blotchy. In some places, concentrations of white chips were grouped together and some areas had concentrations of gray binder exposed, giving the floor an uneven, blotchy appearance.

Unfortunately, there is nothing that can be done to make it look better; it was just the way the chips happened to fall (pun definitely intended). At least now my client could explain the blotchiness to her customer.