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Chapter 25 — GYPSUM PANEL PRODUCTS AND PLASTER

Section 2513 — EXPOSED AGGREGATE PLASTER

2025 California Building Code (Title 24, Part 2) · 2025 edition · updated 2026-07-29 · California

Italicized text is a California amendment to the model code, as printed in the official publication.

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.

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.

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 shall have a minimum compressive strength of 1,000 pounds per square inch (6895 kPa).

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.

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.

Masonry and concrete surfaces shall be prepared in accordance with the provisions of Section 2510.7.

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.

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▸ Contents — 2025 California Building Code (Title 24, Part 2)
2025 California Building Code (Title 24, Part 2)
  1. Chapter 1 — ADMINISTRATION
  2. Chapter 2 — DEFINITIONS
  3. Chapter 3 — OCCUPANCY CLASSIFICATION AND USE
  4. Chapter 4 — SPECIAL DETAILED REQUIREMENTS BASED ON OCCUPANCY A…
  5. Chapter 5 — GENERAL BUILDING HEIGHTS AND AREAS
  6. Chapter 6 — TYPES OF CONSTRUCTION
  7. Chapter 7 — FIRE AND SMOKE PROTECTION FEATURES
  8. Chapter 7A — MATERIALS AND CONSTRUCTION METHODS FOR EXTERIOR W…
  9. Chapter 8 — INTERIOR FINISHES
  10. Chapter 9 — FIRE PROTECTION AND LIFE SAFETY SYSTEMS
  11. Chapter 10 — MEANS OF EGRESS
  12. Chapter 11 — RESERVED
  13. Chapter 11A — HOUSING ACCESSIBILITY
  14. Chapter 11B — ACCESSIBILITY TO PUBLIC BUILDINGS, PUBLIC ACCOMM…
  15. Chapter 12 — INTERIOR ENVIRONMENT
  16. Chapter 13 — ENERGY EFFICIENCY
  17. Chapter 14 — EXTERIOR WALLS
  18. Chapter 15 — ROOF ASSEMBLIES AND ROOFTOP STRUCTURES
  19. Chapter 16 — STRUCTURAL DESIGN
  20. Chapter 16A — STRUCTURAL DESIGN
  21. Chapter 17 — SPECIAL INSPECTIONS AND TESTS
  22. Chapter 17A — SPECIAL INSPECTIONS AND TESTS
  23. Chapter 18 — SOILS AND FOUNDATIONS
  24. Chapter 18A — SOILS AND FOUNDATIONS
  25. Chapter 19 — CONCRETE
  26. Chapter 19A — CONCRETE
  27. Chapter 20 — ALUMINUM
  28. Chapter 21 — MASONRY
  29. Chapter 21A — MASONRY
  30. Chapter 22 — STEEL
  31. Chapter 22A — STEEL
  32. Chapter 23 — WOOD
  33. Chapter 24 — GLASS AND GLAZING
  34. ▸ Chapter 25 — GYPSUM PANEL PRODUCTS AND PLASTER
    Overview
    1. Section 2501 — GENERAL
    2. Section 2502 — PERFORMANCE
    3. Section 2503 — INSPECTION
    4. Section 2504 — VERTICAL AND HORIZONTAL ASSEMBLIES
    5. Section 2505 — SHEAR WALL CONSTRUCTION
    6. Section 2506 — GYPSUM PANEL PRODUCT MATERIALS
    7. Section 2507 — LATHING AND PLASTERING
    8. Section 2508 — GYPSUM CONSTRUCTION
    9. Section 2509 — SHOWERS AND WATER CLOSETS
    10. Section 2510 — LATHING AND FURRING FOR CEMENT PLASTER (STUCCO)
    11. Section 2511 — INTERIOR PLASTER
    12. Section 2512 — EXTERIOR PLASTER
    13. Section 2513 — EXPOSED AGGREGATE PLASTER
    14. Section 2514 — REINFORCED GYPSUM CONCRETE
  35. Chapter 26 — PLASTIC
  36. Chapter 27 — ELECTRICAL
  37. Chapter 28 — MECHANICAL SYSTEMS
  38. Chapter 29 — PLUMBING SYSTEMS
  39. Chapter 30 — ELEVATORS AND CONVEYING SYSTEMS
  40. Chapter 31 — SPECIAL CONSTRUCTION
  41. Chapter 31A — SYSTEMS FOR WINDOW CLEANING OR EXTERIOR BUILDING…
  42. Chapter 31B — PUBLIC POOLS
  43. Chapter 31C — RADIATION
  44. Chapter 31D — FOOD ESTABLISHMENTS
  45. Chapter 31F — MARINE OIL TERMINALS
  46. Chapter 32 — ENCROACHMENTS INTO THE PUBLIC RIGHT-OF-WAY
  47. Chapter 33 — SAFEGUARDS DURING CONSTRUCTION
  48. Chapter 34 — RESERVED
  49. Chapter 35 — REFERENCED STANDARDS
  50. Appendix A — EMPLOYEE QUALIFICATIONS
  51. Appendix B — BOARD OF APPEALS
  52. Appendix C — GROUP U—AGRICULTURAL BUILDINGS
  53. Appendix D — FIRE DISTRICTS
  54. Appendix E — RESERVED
  55. Appendix F — RODENTPROOFING
  56. Appendix G — FLOOD-RESISTANT CONSTRUCTION
  57. Appendix H — SIGNS
  58. Appendix I — PATIO COVERS
  59. Appendix J — GRADING
  60. Appendix K — GROUP R-3 AND GROUP R-3.1 OCCUPANCIES PROTECTED B…
  61. Appendix L — EARTHQUAKE RECORDING INSTRUMENTATION
  62. Appendix M — TSUNAMI-GENERATED FLOOD HAZARDS
  63. Appendix N — REPLICABLE BUILDINGS
  64. Appendix O — PERFORMANCE-BASED APPLICATION
  65. Appendix P — SLEEPING LOFTS
  66. Appendix Q — EMERGENCY HOUSING

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