ASTM C926-21 PDF Download

The ASTM C926-21 standard outlines the requirements for applying full thickness Portland cement-based plaster for both exterior (stucco) and interior work. The standard provides tables for proportioning various plaster mixes and determining the appropriate plaster thickness.

The materials used in the application include cement (such as Portland cement or blended hydraulic cement), Type S hydrated lime, aggregates (like perlite and sand), water, admixtures, and fibers. The specification also addresses the preparation of solid bases, such as masonry or concrete, through sandblasting, wire brushing, acid etching, chipping, or a combination of these methods.

Other topics covered in the standard include curing techniques to resist cracking, materials protection and storage, environmental conditions, and the application of plaster, finish-coat, and fog-coat. These application processes can be done by hand or machine, up to the specified nominal thickness, on both metal and solid plaster bases.

Please note that this specification provides technical requirements for the application of plaster and does not define a unit of work or assign responsibility for contractual purposes. The standard references additional annexes for general information and design considerations and includes notes and footnotes that offer explanatory material. For specific fire resistance construction details, the standard recommends obtaining information from reports of fire-resistance tests, engineering evaluations, or recognized fire testing laboratories.