Portland Cement-Based Plaster and Stucco Specifications

Today, stucco is valued for masonry, as the plaster allows for complex aesthetic details in buildings and structures. A contemporary marvel, stucco actually dates back to ancient times. In fact, the peculiar word “stucco” derives from 1590s Italian, and it may even have deeper Proto-Germanic roots.

Many ancient and historical examples of stucco have persisted until today—a structural accomplishment considering that these relics precede modern innovations. Stucco faced a monumental change in 1824, with the discovery of cement.

For stucco and plaster, the ancient Greeks and Romans utilized a volcanic ash mixture. Today, while plaster comes in various types, portland cement has been responsible for granting substantial strength to the plasters that contain it.

It is, however, important to recognize the difference between stucco and plaster. While some may classify stucco or plaster as utilizing separate binding materials (e.g. gypsum or cement), this may not be wholly accurate. Instead, in English, plaster broadly is thought of being used entirely for interior use and stucco for exterior applications. Both consist of a binder, aggregates, and water.

Standards for Plaster and Stucco Containing Portland Cement

Standard practices and specifications for the materials in or in contact with plaster and stucco, as well as those for their application, can help assure the strength and reliability that is inherent with the inclusion of portland cement.

For example, ASTM C926-20: Standard Specification for Application of Portland Cement-Based Plaster covers guidelines for the application of full thickness portland cement-based plaster or stucco for exterior and interior work. It does not define a unit of work or assign responsibility for contractual purposes.

There are numerous other ASTM International standards for portland cement-based plaster and stucco. These include:

ASTM C1328/C1328M-19: Standard Specification for Plastic (Stucco) Cement

ASTM C1764-12(2018): Standard Test Methods for Non Metallic Plaster Bases (Lath) Used with Portland Cement Based Plaster in Vertical Wall Applications

ASTM C1788-14(2019): Standard Specification for Non Metallic Plaster Bases (Lath) Used with Portland Cement Based Plaster in Vertical Wall Applications

ASTM C1787-14(2019): Standard Specification for Installation of Non Metallic Plaster Bases (Lath) Used with Portland Cement Based Plaster in Vertical Wall Applications

ASTM C1063-17b: Standard Specification for Installation of Lathing and Furring to Receive Interior and Exterior Portland Cement-Based Plaster

ASTM C1861-18: Standard Specification for Lathing and Furring Accessories, and Fasteners, for Interior and Exterior Portland Cement-Based Plaster

ASTM C897-15: Standard Specification for Aggregate for Job-Mixed Portland Cement-Based Plasters