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Chapter 25 — GYPSUM BOARD, GYPSUM PANEL PRODUCTS AND PLASTER

Section 2509

California Building Code (Title 24, Part 2) · 2019 edition · updated 2026-09-12 · California

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

2509.1 Wet areas.

Showers and public toilet walls shall conform to Section 1210.2.

2509.2 Base for tile.

Materials used as a base for wall tile in tub and shower areas and wall and ceiling panels in shower areas shall be of materials listed in Table 2509.2 and installed in accordance with the manufacturer’s recommendations. Water-resistant gypsum backing board shall be used as a base for tile in water closet compartment walls when installed in accordance with GA-216 or ASTM C840 and the manufacturer’s recommendations. Regular gypsum wallboard is permitted under tile or wall panels in other wall and ceiling areas when installed in accordance with GA-216 or ASTM C840.

2509.3 Limitations.

Water-resistant gypsum backing board shall not be used in the following locations:

  1. Over a vapor retarder in shower or bathtub compartments.

  2. Where there will be direct exposure to water or in areas subject to continuous high humidity.

398 2019 CALIFORNIA BUILDING CODE

Copyright © 2019 ICC. ALL RIGHTS RESERVED. Accessed by Kevin Day (kevin.day@dgs.ca.gov), (California Building Standards Commission) Order Number #100735044 on Jul 24, 2019 03:54 PM (PDT) pursuant to License Agreement with ICC. No further reproduction or distribution authorized. Single user only, copying and networking prohibited. ANY UNAUTHORIZED REPRODUCTION OR DISTRIBUTION IS A VIOLATION OF THE FEDERAL COPYRIGHT ACT AND THE LICENSE AGREEMENT, AND SUBJECT TO CIVIL AND CRIMINAL PENALTIES THEREUNDER.

100735044

GYPSUM BOARD, GYPSUM PANEL PRODUCTS AND PLASTER

TABLE 2508.6 SHEAR CAPACITY FOR HORIZONTAL WOOD-FRAME GYPSUM BOARD DIAPHRAGM CEILING ASSEMBLIES

MATERIAL THICKNESS
OF MATERIAL
(MINIMUM) (inches)		 SPACING
OF FRAMING
MEMBERS (inches)		 SHEAR
VALUEa, b
(PLF OF CEILING)		 MIMIMUM FASTENER SIZE
Gypsum board or gypsum
panel product		 1/2 16 o.c. 90 5d cooler or wallboard nail;
15/8-inch long; 0.086-inch shank;
15/64-inch headc
Gypsum board or gypsum
panel product		 1/2 24 o.c. 70 5d cooler or wallboard nail;
15/8-inch long; 0.086-inch shank;
15/64-inch headc

For SI: 1 inch = 25.4 mm, 1 pound per foot = 14.59 N/m. a. Values are not cumulative with other horizontal diaphragm values and are for short-term wind or seismic loading. Values shall be reduced 25 percent for

normal loading. b. Values shall be reduced 50 percent in Seismic Design Categories D, E and F. c. 1 1 /4-inch, No. 6 Type S or W screws are permitted to be substituted for the listed nails.

TABLE 2509.2

BACKERBOARD MATERIALS
MATERIAL STANDARD
Glass mat gypsum backing panel ASTM C1178
Nonasbestos fiber-cement backer
board		 ASTM C1288 or ISO 8336,
Category C
Nonasbestos fiber-mat reinforced
cementitious backer unit		 ASTM C1325

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▸Contents — California Building Code (Title 24, Part 2)
California Building Code (Title 24, Part 2)
  1. Chapter 2 — DEFINITIONS AND ABBREVIATIONS
  2. Appendix G — FLOOD-RESISTANT
  3. Appendix L — EARTHQUAKE RECORDING
  4. Appendix M — TSUNAMI-GENERATED
  5. Chapter 1 — SCOPE AND ADMINISTRATION
  6. Chapter 3 — OCCUPANCY CLASSIFICATION AND USE
  7. Chapter 4 — SPECIAL DETAILED REQUIREMENTS BASED
  8. Chapter 5 — GENERAL BUILDING HEIGHTS AND AREAS
  9. Chapter 6 — TYPES OF CONSTRUCTION
  10. Chapter 7 — FIRE AND SMOKE PROTECTION FEATURES
  11. Chapter 7A — MATERIALS AND CONSTRUCTION
  12. Chapter 8 — INTERIOR FINISHES
  13. Chapter 9 — FIRE PROTECTION AND LIFE SAFETY SYSTEMS
  14. Chapter 10 — MEANS OF EGRESS
  15. Chapter 11A — HOUSING ACCESSIBILITY
  16. Chapter 11B — ACCESSIBILITY TO PUBLIC BUILDINGS, PUBLIC ACCOMM…
  17. Chapter 12 — INTERIOR ENVIRONMENT
  18. Chapter 14 — EXTERIOR WALLS
  19. Chapter 15 — ROOF ASSEMBLIES AND ROOFTOP STRUCTURES
  20. Chapter 16 — STRUCTURAL DESIGN
  21. Chapter 16A — STRUCTURAL DESIGN
  22. Chapter 17 — SPECIAL INSPECTIONS AND TESTS
  23. Chapter 18 — SOILS AND FOUNDATIONS
  24. Chapter 19 — CONCRETE
  25. Chapter 20 — ALUMINUM
  26. Chapter 21 — MASONRY
  27. Chapter 22 — STEEL
  28. Chapter 23 — WOOD
  29. Chapter 24 — GLASS AND GLAZING
  30. ▸Chapter 25 — GYPSUM BOARD, GYPSUM PANEL PRODUCTS AND PLASTER
    Overview
    1. Section 2501
    2. Section 2502
    3. Section 2503
    4. Section 2504
    5. Section 2505
    6. Section 2506
    7. Section 2507
    8. Section 2508
    9. Section 2509
    10. Section 2510
    11. Section 2511
    12. Section 2512
    13. Section 2513
    14. Section 2514
  31. Chapter 26 — PLASTIC
  32. Chapter 27 — ELECTRICAL
  33. Chapter 28 — MECHANICAL SYSTEMS
  34. Chapter 30 — ELEVATORS AND CONVEYING SYSTEMS
  35. Chapter 31 — SPECIAL CONSTRUCTION
  36. Chapter 31B — PUBLIC POOLS
  37. Chapter 31C — RADIATION
  38. Chapter 31D — FOOD ESTABLISHMENTS
  39. Chapter 31F — MARINE OIL TERMINALS
  40. Chapter 32 — ENCROACHMENTS INTO THE PUBLIC RIGHT-OF-WAY
  41. Chapter 33 — SAFEGUARDS DURING CONSTRUCTION
  42. Chapter 35 — REFERENCED STANDARDS
  43. Appendix A — EMPLOYEE QUALIFICATIONS
  44. Appendix B — BOARD OF APPEALS
  45. Appendix C — GROUP U – AGRICULTURAL BUILDINGS
  46. Appendix D — FIRE DISTRICTS
  47. Appendix F — RODENTPROOFING
  48. Appendix H — SIGNS
  49. Appendix I — PATIO COVERS
  50. Appendix J — GRADING
  51. Appendix K — GROUP R-3 AND GROUP R-3.1 OCCUPANCIES
  52. Appendix N — REPLICABLE BUILDINGS
  53. Appendix O — EMERGENCY HOUSING

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