ASTM C926-22 PDF Download

The ASTM C926-22 standard outlines the requirements for applying full-thickness Portland cement-based plaster for both exterior (stucco) and interior work. The standard provides guidance on the proportions of various plaster mixes and the thickness of the plaster.

The materials used in this specification include Portland cement, air-entraining Portland cement, masonry cement, blended hydraulic cement, air-entraining blended hydraulic cement, plastic cement, Type S hydrated lime, aggregates such as perlite and sand for base and job-mixed finish coats, water, admixtures, and fibers.

The standard also addresses the preparation of surfaces, such as masonry, stone, cast-in-place or precast concrete, by methods such as sandblasting, wire brushing, acid etching, chipping, or a combination of these techniques. It includes details on curing to resist cracking, materials protection and storage, environmental conditions, and application of plaster, finish-coat, and fog-coat. These applications can be done either manually or by machine, up to the specified nominal thickness on metal and solid plaster bases.

The scope of the standard clarifies that it defines the technical requirements for the application of full-thickness Portland cement-based plaster but does not define a unit of work or assign responsibility for contractual purposes, which is determined by the contracts made between contracting entities. The standard references additional information in Annex A1 and Annex A2, which provide general information and design considerations, respectively. The notes and footnotes in the specification are for explanatory purposes and are not considered requirements of the standard. Specific construction details to achieve the required fire resistance should be obtained from reports of fire-resistance tests, engineering evaluations, or listings from recognized fire testing laboratories.