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Chapter 3 — BUILDING PLANNING

Section R337.9

California Residential Code (Title 24, Part 2.5) · 2022 edition · updated 2026-09-12 · California

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

DECKING R337.9.1 General. The walking surface material of decks, porches, balconies and stairs shall comply with the requirements of this section.

R337.9.1.1 Flashing. A minimum of a 6-inch (150 mm) metal flashing, applied vertically on the exterior of the wall, shall be installed at all deck-to-wall intersections. R337.9.2 Where required. The walking surface material of decks, porches, balconies and stairs shall comply with the requirements of this section when any portion of such surface is within 10 feet (3048 mm) of the building.

R337.9.3 Decking surfaces. The walking surface material of decks, porches, balconies and stairs shall be con- structed with one of the following materials:

1. Material that complies with the performance requirements of Section R337.9.4 when tested in accordance with both ASTM E2632 and ASTM E2726.

2. Ignition-resistant material that complies with the performance requirements of Section R337.9.4.

3. Material that complies with the performance requirements of both SFM Standard 12-7A-4 and Section R337.4.3.

4. Exterior fire-retardant-treated wood.

5. Noncombustible material.

6. Any material that complies with the performance requirements of SFM Standard 12-7A-4A when attached exterior wall covering is also composed of noncombustible or ignition-resistant material.

Exception: Wall material shall be permitted to be of any material that otherwise complies with this chapter when the decking surface material com- plies with the performance requirements ASTM E84 with a Class B flame spread index. 7. Any material that complies with the performance requirements of Section R337.9.5 when tested in accordance with ASTM E2632 and when attached exterior wall covering is also composed of only non- combustible or ignition-resistant materials.

Exception : Wall material shall be permitted to be of any material that otherwise complies with this chapter when the decking surface material com-

3-104 2022 CALIFORNIA RESIDENTIAL CODE

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BUILDING PLANNING

wildfires shall be constructed to conform to the ignition- resistance requirements of this section.

R337.10.2 Applicability. Unless otherwise addressed by the exceptions of Section R337.1.3, the provisions of this section shall apply to buildings accessory to an applicable building on the same lot. This section shall also apply to attached and detached miscellaneous structures that require a building permit, including but not limited to; trellises, arbors, patio covers, gazebos and similar struc- tures.

Exceptions:

1. Decks shall comply with the requirements of Sec- tion R337.9.

2. Awnings and canopies shall comply with the requirements of Section 3105 of the California Building Code.

3. Exterior wall architectural trim, embellishments and fascia. R337.10.3 Where required. Miscellaneous structures that require a permit, and accessory buildings of any size, when separated from an applicable building on the same lot by a distance of less than 3 feet (914 mm), shall comply with Section R337.10.3.1. Accessory buildings that are greater than 120 square feet (11 m 2 ), when separated from an applicable building on the same lot by a distance of 3 feet (914 mm) or more but less than 50 feet (15 m) shall comply with Section R337.10.3.2.

When required by the enforcing agency, miscellaneous structures that require a permit, and accessory buildings that are 120 square feet (11 m 2 ) or less, when separated from an applicable building on the same lot by a distance of 3 feet (914 mm) or more but less than 50 feet (15 m), shall comply with either Section R337.10.3.4 or Section R337.10.3.3, respectively.

No requirements shall apply to accessory buildings or miscellaneous structures when located 50 feet (15 m) or more from an applicable building on the same lot.

R337.10.3.1 Structures and accessory buildings within 3 feet (914 mm). Miscellaneous structures that require a permit, and accessory buildings attached to or separated from an applicable building on the same lot by a distance of less than 3 feet (914 mm) shall be constructed of noncombustible materials or of ignition- resistant materials as described in Section R337.4.2.

R337.10.3.2 Accessory buildings greater than 120 square feet (11 m 2 ), located 3 feet (914 mm) or more but less than 50 feet (15 m). Accessory buildings that are greater than 120 square feet (11 m 2 ) in size and separated from an applicable building on the same lot by a distance of 3 feet (914 mm) or more but less than 50 feet (15 m) shall be constructed of noncombustible materials or of ignition- resistant materials as described in Section R337.4.2.

R337.10.3.3 Accessory buildings 120 square feet (11 m 2 ) or less, located 3 feet (914 mm) or more but less than 50 feet (15 m). When required by the enforcing agency, accessory buildings 120 square feet (11 m 2 ) or less and

plies with the performance requirements ASTM E84 with a Class B flame spread index.

R337.9.4 Requirements for type of material in Section R337.9.3, Item 1. The material shall be tested in accor- dance with both ASTM E2632 and ASTM E2726 and shall comply with the conditions of acceptance in Sections R337.9.4.1 and R337.9.4.2. The material shall also be tested in accordance with ASTM E84 or UL 723 and com- ply with the performance requirements of Section R337.4.3.

9.4 Requirements for type of material in Section_** R337.9.3, Item 1. The material shall be tested in accor- dance with both ASTM E2632 and ASTM E2726 and shall comply with the conditions of acceptance in Sections R337.9.4.1 and R337.9.4.2. The material shall also be tested in accordance with ASTM E84 or UL 723 and com- ply with the performance requirements of Section R337.4.3.

R337.9.4.1 Conditions of acceptance for ASTM E2632. The ASTM E2632 test shall be conducted on a minimum of three test specimens and the conditions of acceptance in Items 1 through 3 below shall be met. If any one of the three tests does not meet the conditions of acceptance, three additional tests shall be run. All of the additional tests shall meet the conditions of acceptance.

1. Peak heat release rate of less than or equal to 25 kW/ft 2 (269 kW/m 2 ).

2. Absence of sustained flaming or glowing combus- tion of any kind at the conclusion of the 40-minute observation period.

3. Absence of falling particles that are still burning when reaching the burner or floor.

R337.9.4.2 Conditions of acceptance for ASTM E2726. The ASTM E2726 test shall be conducted, using a “Class A” size roof test brand, on a minimum of three test specimens and the conditions of acceptance in Items 1 and 2 below shall be met. If any one of the three test specimens does not meet the conditions of accep- tance, three additional tests shall be run. All of the additional tests shall meet the conditions of accep- tance.

1. Absence of sustained flaming or glowing combus- tion of any kind at the conclusion of the 40-min- ute observation period.

2. Absence of falling particles that are still burning when reaching the burner or floor.

R337.9.5 Requirements for type of material in Section R337.9.3, Item 7. The material shall be tested in accor- dance with ASTM E2632 and shall comply with the follow- ing condition of acceptance. The ASTM E2632 test shall be conducted on a minimum of three test specimens and the peak heat release rate shall be less than or equal to 25 kW/ft 2 (269 kW/m 2 ). If any one of the three tests does not meet the conditions of acceptance, three additional tests shall be run. All the additional tests shall meet the condi- tion of acceptance.

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▸Contents — California Residential Code (Title 24, Part 2.5)
California Residential Code (Title 24, Part 2.5)
  1. Chapter 2 — DEFINITIONS AND ABBREVIATIONS
  2. Appendix AF — RADON CONTROL
  3. Appendix AI — PRIVATE SEWAGE
  4. Appendix AJ — EXISTING
  5. Appendix AK — SOUND
  6. Appendix AO — AUTOMATIC
  7. Appendix AR — LIGHT STRAW-CLAY
  8. Appendix AS — STRAWBALE
  9. Appendix AU — COB CONSTRUCTION
  10. Appendix AV — BOARD
  11. Appendix AW — 3D-PRINTED BUILDING
  12. Chapter 1 — SCOPE AND APPLICATION
  13. ▸Chapter 3 — BUILDING PLANNING
    Overview
    1. Section R300
    2. Section R301
    3. Section R302
    4. Section R303
    5. Section R304
    6. Section R305
    7. Section R307
    8. Section R308
    9. Section R306
    10. Section R309
    11. Section R310
    12. Section R311
    13. Section R312
    14. Section R313
    15. Section R314
    16. Section R315
    17. Section R316
    18. Section R317
    19. Section R318
    20. Section R319
    21. Section R320
    22. Section R321
    23. Section R322
    24. Section R323
    25. Section R324
    26. Section R325
    27. Section R327
    28. Section R326
    29. Section R328
    30. Section R329
    31. Section R330
    32. Section R334
    33. Section R335
    34. Section R336
    35. Section R337
    36. Section R337.1
    37. Section R337.2
    38. Section R337.3
    39. Section R337.4
    40. Section R337.5
    41. Section R337.6
    42. Section R337.7
    43. Section R337.8
    44. Section R337.9
    45. Section R337.10
    46. Section R338
    47. Section R340
  14. Chapter 4 — FOUNDATIONS
  15. Chapter 5 — FLOORS
  16. Chapter 6 — WALL CONSTRUCTION
  17. Chapter 7 — WALL COVERING
  18. Chapter 8 — ROOF-CEILING CONSTRUCTION
  19. Chapter 9 — ROOF ASSEMBLIES
  20. Chapter 10 — CHIMNEYS AND FIREPLACES
  21. Chapter 44 — REFERENCED STANDARDS
  22. Appendix AH — PATIO COVERS
  23. Appendix AL — PERMIT FEES
  24. Appendix AQ — TINY HOUSES
  25. Appendix AT — SOLAR-READY PROVISIONS—DETACHED ONE- AND
  26. Appendix AX — SWIMMING POOL SAFETY ACT
  27. Appendix AY — AREAS PROTECTED BY THE FACILITIES
  28. Appendix AZ — EMERGENCY HOUSING

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