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Chapter 12 — INTERIOR ENVIRONMENT

Section 1206 — SOUND TRANSMISSION

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.

1206.1 Scope.

This section shall apply to common interior walls, partitions and floor/ceiling assemblies between adjacent dwelling units and sleeping units or between dwelling units and sleeping units and adjacent public areas.

1206.2 Airborne sound.

Walls, partitions and floor-ceiling assemblies separating dwelling units and sleeping units from each other or from public or service areas shall have a sound transmission class of not less than 50 where tested in accordance with ASTM E90, or have a Normalized Noise Isolation Class (NNIC) rating of not less than 45 if field tested, in accordance with ASTM E336 for airborne noise. Alternatively, the sound transmission class of walls, partitions and floor-ceiling assemblies shall be established by engineering analysis based on a comparison of walls, partitions and floor-ceiling assemblies having sound transmission class ratings as determined by the test procedures set forth in ASTM E90. Engineering analysis shall be performed by a registered design professional. Penetrations or openings in construction assemblies for piping; electrical devices; recessed cabinets; bathtubs; soffits; or heating, ventilating or exhaust ducts shall be sealed, lined, insulated or otherwise treated to maintain the required ratings. This requirement shall not apply to entrance doors; however, such doors shall be tight fitting to the frame and sill.

1206.2.1 Masonry. The sound transmission class of concrete masonry and clay masonry assemblies shall be calculated in accordance with TMS 302 or determined through testing in accordance with ASTM E90.

1206.3 Structure-borne sound.

Floor-ceiling assemblies between dwelling units and sleeping units or between a dwelling unit or sleeping unit and a public or service area within the structure shall have an impact insulation class rating of not less than 50 where tested in accordance with ASTM E492, or have a Normalized Impact Sound Rating (NISR) of not less than 45 if field tested in accordance with ASTM E1007. Alternatively, the impact insulation class of floor-ceiling assemblies shall be established by engineering analysis based on a comparison of floor-ceiling assemblies having impact insulation class ratings as determined by the test procedures in ASTM E492. Engineering analysis shall be performed by a registered design professional.

Exception: Impact sound insulation is not required for floor-ceiling assemblies over nonhabitable rooms or spaces not designed to be occupied, such as garages, mechanical rooms or storage areas.

1206.4 Allowable interior noise levels.

Interior noise levels attributable to exterior sources shall not exceed 45 dB in any habitable room. The noise metric shall be either the day-night average sound level (Ldn) or the community noise equivalent level (CNEL), consis- tent with the noise element of the local general plan.

1206.5 Acoustical control.

1206.5 Acoustical control. [BSC-CG] See California Green Building Standards Code, Chapter 5, Division 5.5 for additional sound trans- mission requirements.

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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
    Overview
    1. Section 1201 — GENERAL
    2. Section 1202 — VENTILATION
    3. Section 1203 — TEMPERATURE CONTROL
    4. Section 1204 — LIGHTING
    5. Section 1205 — YARDS OR COURTS
    6. Section 1206 — SOUND TRANSMISSION
    7. Section 1207 — ENHANCED CLASSROOM ACOUSTICS
    8. Section 1208 — INTERIOR SPACE DIMENSIONS
    9. Section 1209 — ACCESS TO UNOCCUPIED SPACES
    10. Section 1210 — TOILET AND BATHROOM REQUIREMENTS
    11. Section 1211 — UV GERMICIDAL IRRADIATION SYSTEMS
    12. Section 1212 — [HCD 1 & HCD 2]—GARAGE DOOR SPRINGS
    13. Section 1213 — [HCD 1]—POLLUTANT CONTROL
    14. Section 1214 — RESERVED
    15. Section 1215 — RESERVED
    16. Section 1216 — RESERVED
    17. Section 1217 — RESERVED
    18. Section 1218 — RESERVED
    19. Section 1219 — RESERVED
    20. Section 1220 — RESERVED
    21. Section 1221 — RESERVED
    22. Section 1222 — RESERVED
    23. Section 1223 — RESERVED
    24. Section 1224 — [OSHPD 1]—HOSPITALS
    25. Section 1225 — [OSHPD 2]-SKILLED NURSING AND INTERMEDIATE-CARE…
    26. Section 1226 — [OSHPD 3]-CLINICS
    27. Section 1227 — [OSHPD 4]-CORRECTIONAL TREATMENT CENTERS
    28. Section 1228 — [OSHPD 5]—ACUTE PSYCHIATRIC HOSPITALS
    29. Section 1229 — [OSHPD 6] — CHEMICAL DEPENDENCY RECOVERY HOSPIT…
    30. Section 1230 — [BSCC] — MINIMUM STANDARDS FOR JUVENILE FACILIT…
    31. Section 1231 — [BSCC] — LOCAL DETENTION
    32. Section 1232 — RESERVED
    33. Section 1233 — RESERVED
    34. Section 1234 — RESERVED
    35. Section 1235 — [DPH]—SANITARY CONTROL OF SHELLFISH (PLANTS AND…
    36. Section 1236 — [DPH]—LABORATORY ANIMAL QUARTERS
    37. Section 1237 — [DPH]—WILD ANIMAL QUARANTINE FACILITIES
    38. Section 1238 — RESERVED
    39. Section 1239 — RESERVED
    40. Section 1240 — [AGR]—MEAT AND POULTRY PROCESSING PLANTS
    41. Section 1241 — [AGR]—COLLECTION CENTERS AND FACILITIES
    42. Section 1242 — [AGR]—RENDERERS
    43. Section 1243 — [AGR]—HORSEMEAT AND PET FOOD ESTABLISHMENTS
    44. Section 1244 — RESERVED
    45. Section 1245 — RESERVED
    46. Section 1246 — RESERVED
    47. Section 1247 — RESERVED
    48. Section 1248 — RESERVED
    49. Section 1249 — RESERVED
    50. Section 1250 — [CA]—PHARMACIES
    51. Section 1251 — [CA]—VETERINARY PREMISES
    52. Section 1252 — [CA]—BARBER COLLEGES AND SHOPS
    53. Section 1253 — [CA]—SCHOOLS OF COSMETOLOGY, COSMETOLOGICAL EST…
    54. Section 1254 — [CA]—ACUPUNCTURE OFFICES
  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
  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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