Pinholes in Terrazzo Flooring


The Groutless® Solution to Pinholes in Terrazzo Flooring


For as long as terrazzo has been installed, pinholes have always been a common characteristic of the flooring. To remedy this a “grouting” process is performed which is to fill all the voids and pinholes in terrazzo flooring. It is a labor-intensive, painstaking but necessary and important process to produce the desired finish. Pinholes have always been a point of contention between contractors and architects as to what level is acceptable in the industry.


Today with epoxy terrazzo being the most commonly specified terrazzo system this issue has only intensified. Concord Terrazzo Company will discuss in detail what pinholes are and our revolutionizing new system in dramatically reducing the number of pinholes initially and throughout the life cycle of an epoxy terrazzo floor.


What are Pinholes?

Pinholes are small air pockets that form during the mixing and application of the terrazzo components. When terrazzo is ground to reveal the aggregates, the pinholes begin to appear. These voids are hard to see from a distance, but their presence exists on the terrazzo floor. Over time, pinholes can affect the shine of a terrazzo floor and can accumulate dirt and grime. For years terrazzo contractors address pinholes by grouting the terrazzo floor.

Pinholes in Terrazzo Flooring

Example of pinholes in a terrazzo floor. Air pockets form tiny circles which installers will grout over

What is Grouting?

Grouting is a stage right after the terrazzo installer has finished grinding the terrazzo floor exposing all the strips and aggregate to give the surface its smooth texture. During the grouting stage, and an installer will grout the terrazzo floor to fill all pinholes and voids found in the floor. For epoxy terrazzo, installers will mix a small portion of the epoxy and apply it to the floor’s surface working the epoxy back and forth with a trowel filling the pinholes. After the grout has been tightly troweled a dusting of filler powder is applied and worked over the floor by various methods to assist the filling of the pinholes. This step is then repeated for each color in the terrazzo design.


Furthermore, after the completion of a project, if the architect finds the floor finish to be objectionable due to the level of pinholes, the item is placed on the project’s punch list. The resolution is typically very time-consuming and causes great expense for the terrazzo contractor to resolve.


Even after the acceptance of the new floor. New pinholes may appear during the floor’s lifecycle commonly caused by regular floor maintenance. Often the terrazzo contractor is not brought back to fix the issue due to its cost and time requirements.


According to the National Terrazzo and Mosaic Association, pinholes are the nature of the terrazzo product. Pinholes do not indicate a loss of performance or a lack of integrity. In fact, when pinholes appear to a minor extent in areas of a terrazzo floor, they would be considered normal by industry standards. With regular maintenance, recommended sealers will typically fill and close the majority of tiny pinholes.


Even though these are the industry standards set forth by the NTMA the definition of “minor” is very subjective with architects and is the cause of much debate.

Grouting Terrazzo

Installers grouting terrazzo using our original TERRAZZCO EZPour Epoxy 158 formula, which we updated to Groutless® in 2019.

A Groutless® Solution

At Concord Terrazzo Company, we’re constantly exploring innovative ways to improve all of our terrazzo products to benefit the environment and the people who interact with our terrazzo floors. In addressing the issue of pinholes in epoxy terrazzo floors, we developed a revolutionary new formula called TERRAZZCO® Groutless® EZPour Epoxy 158. TERRAZZCO® Groutless® EZPour Epoxy 158 is a pigmented, 100% solid (VOC free), two-part epoxy resin system formulated to cure with dramatically fewer pinholes thus reducing the amount of labor required in the grouting phase of any terrazzo project. This factor leads to lower labor costs and reduces the installation time. In addition to dramatically fewer pinholes during the installation process, the terrazzo floor is also less likely to develop new pinholes commonly caused by regular floor maintenance during the life span of the floor.


At the time of development, various terrazzo contractors conducted test trials for Concord Terrazzo Company using the new Groutless® formula. The results were highly conclusive. Not only did Groutless® EZPour Epoxy 158 dramatically reduce the number of pinholes but in over 50% of the installations, no grouting was required.


Navicent Health Children’s Hospital – Terrazzo Floor using Groutless®

Grouting can be a daunting task for many terrazzo installers and an exasperation with architects. Groutless® benefits installers by reducing bodily stress over the course of their careers while helping terrazzo contractors and architects reduce labor and material costs while helping to expedite project completion times and increasing the overall satisfaction of a terrazzo’s finish for years to come.


If you are interested in eliminating the issue of pinholes from a terrazzo project while maintaining the highest level of quality, request or specify TERRAZZCO® Groutless® EZPour Epoxy 158 and see for yourself how our new Groutless® is an industry game-changer. For inquiries please email us at