Sustainable, Cost-Effective Renovations Using Terrazzo

Minimize demolition and optimize durability
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Sponsored by National Terrazzo & Mosaic Association (NTMA)
By Peter J. Arsenault, FAIA, NCARB, LEED-AP

Specifying Terrazzo Installations

When specifying terrazzo, it is advisable to review the information available from NTMA, which publishes industry standards and model specifications that can be customized for specific construction or renovation projects. In a standard, three-part specification format following the CSI or MasterFormat system, it is found in Division 9: Finishes under Section 09 66 23. Some of the relevant items to address are highlighted as follows.

Part 1: General

The scope of the specified work and related work as well as any definitions should be called out. It is advisable to specify a preinstallation meeting and request submittals based on the project needs, including the request for LEED documentation for credits being pursued. Quality assurance can be addressed by calling for Contractor and Associate membership in NTMA, which represents a commitment to meeting NTMA standards and protocols. Project conditions and product storage should all be addressed in typical fashion.

Part 2: Products

All of the different performance and material criteria for each of the components of a terrazzo system need to be called out. This includes the bonding matrix, primer (if required), aggregates, divider strips, and abrasive strips (for stairs if needed). If any precast terrazzo is part of the project, the types, sizes, makeups, colors, patterns, and finishes will all need to be specified. The setting materials for precast terrazzo will also need to be called out. There may be some miscellaneous accessories needed for either poured-in-place or precast terrazzo, including sealers, moisture-mitigation products, or a crack-suppression/isolation membrane. Each should be called out as required.

The details of each mix of terrazzo that is being used in the project will need to be clearly identified in the specifications and coordinated with locations as shown on the drawings. NTMA has published standard color plates and mix colors from which selections can be made. If custom colors are required, they are readily possible, but they need to be identified and specified according to the resin color and chip (aggregate) mix, showing the size, grade, and percentage of the total mix that each chip provides.

Walnut Grove Elementary School located in Bargersville, Indiana, incorporated seven bright, cheerful colors that were each specified to enhance the creative and way-finding aspects of the design.

Part 3: Execution

As with any site-installed product, the installation requires multiple steps that need to be clearly articulated in the specification in order to achieve the best results, including:

  • Examination and preparation: The importance of this step should always be stressed. In addition to the architect, the installer and general contractor or construction manager should review and examine the substrate for conditions that may affect the installation or the overall performance. This can include a determination that the slab does not vary more than 14 inch from a true plan in a 10-foot span. It may also require the use of independent testing agencies to verify moisture content in the slab. Any issues will need to be corrected, likely by the general contractor, if they are found to be out of compliance with the stated requirements.
  • Installation: For poured-in-place installations, the divider strips are installed, and the terrazzo is placed, finished, and polished as specified. For precast terrazzo, the surface is prepared, and the terrazzo is installed using the specified bonding agent.
  • Protection: Once installed and finished, the surface should be able to withstand use by remaining construction personnel on the project. However, the general contractor should be instructed to cover and protect the surface as appropriate to the job-site conditions.
  • Cleaning: Upon completion, the terrazzo should be cleaned of any construction or miscellaneous dirt, debris, etc. following the directions from NTMA on cleaning and maintenance.

When specified and installed correctly, the floor system will provide the desired look and long-term performance characteristics that are intended.

Conclusion

Terrazzo has been shown to provide architects, interior designers, construction professionals, and building owners/managers with an appealing, long-lasting solution for floors and other interior building surfaces. It offers exceptional design versatility with numerous options and complete customization possibilities. Its performance is well-known and documented for durability, ease of maintenance, and resistance to many conditions due to its nonporous nature. As a sustainable system, it can contribute to LEED and other green building certifications. Overall, it has been used for more than 100 years in the United States and continues to be a popular, enduring, affordable choice in both new construction and renovation.

 

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Originally published in Architectural Record
Originally published in June 2021

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