Chapter 25 — GYPSUM PANEL PRODUCTS AND PLASTER
Section 2513 — EXPOSED AGGREGATE PLASTER
2025 California Building Code (Title 24, Part 2) · 2025 edition · ingested 2026-07-07 · California
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2513.1 General. ¶
2513.1 General. Exposed natural or integrally colored aggregate is permitted to be partially embedded in a natural or colored bedding coat of cement plaster or gypsum plaster, subject to the provisions of this section.
2513.2 Aggregate. ¶
2513.2 Aggregate. The aggregate shall be applied manually or mechanically and shall consist of marble chips, pebbles or similar durable, moderately hard (three or more on the Mohs hardness scale), nonreactive materials.
2513.3 Bedding coat proportions. ¶
2513.3 Bedding coat proportions. The bedding coat for interior or exterior surfaces shall be composed of one part Portland cement and one part Type S lime; or one part blended cement and one part Type S lime; or masonry cement; or plastic cement and not more than three parts of graded white or natural sand by volume. The bedding coat for interior surfaces shall be composed of 100 pounds (45.4 kg) of neat gypsum plaster and not more than 200 pounds (90.8 kg) of graded white sand. A factory-prepared bedding coat for interior or exterior use is permitted. The bedding coat for exterior surfaces…
2513.4 Application. ¶
2513.4 Application. The bedding coat is permitted to be applied directly over the first (scratch) coat of plaster, provided that the ultimate overall thickness is not less than [7] / 8 inch (22 mm), including lath. Over concrete or masonry surfaces, the overall thickness shall be not less than [1] / 2 inch (12.7 mm).
2513.5 Bases. ¶
2513.5 Bases. Exposed aggregate plaster is permitted to be applied over concrete, masonry, cement plaster base coats or gypsum plaster base coats installed in accordance with Section 2511 or 2512.
2513.6 Preparation of masonry and concrete. ¶
2513.6 Preparation of masonry and concrete. Masonry and concrete surfaces shall be prepared in accordance with the provisions of Section 2510.7.
2513.7 Curing of base coats. ¶
2513.7 Curing of base coats. Cement plaster base coats shall be cured in accordance with ASTM C926. Cement plaster bedding coats shall retain sufficient moisture for hydration (hardening) for 24 hours minimum or, where necessary, shall be kept damp for 24 hours by light water spraying.