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Appendix BJ — STRAWBALE CONSTRUCTION

Section BJ108 — THERMAL INSULATION

2025 California Residential Code (Title 24, Part 2.5) · 2025 edition · updated 2026-07-27 · California

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

BJ108.1 R-value.

The unit R-value of a strawbale wall with bales laid flat is R-1.55 for each inch of bale thickness. The unit R-value of a strawbale wall with bales on-edge is R-1.85 for each inch of bale thickness.

BJ108.2 Compliance with Section R302.10.1.

Straw bales meet the requirements for insulation materials in Section R302.10.1 for flame spread index and smoke-developed index as tested in accordance with ASTM E84.

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▸ Contents — 2025 California Residential Code (Title 24, Part 2.5)
2025 California Residential Code (Title 24, Part 2.5)
  1. Chapter 1 — ADMINISTRATION
  2. Chapter 2 — DEFINITIONS
  3. Chapter 3 — BUILDING PLANNING
  4. Chapter 4 — FOUNDATIONS
  5. Chapter 5 — FLOORS
  6. Chapter 6 — WALL CONSTRUCTION
  7. Chapter 7 — WALL COVERING
  8. Chapter 8 — ROOF-CEILING CONSTRUCTION
  9. Chapter 9 — ROOF ASSEMBLIES
  10. Chapter 10 — CHIMNEYS AND FIREPLACES
  11. Chapter 44 — REFERENCED STANDARDS
  12. Appendix AA — BOARD OF APPEALS
  13. Appendix AB — PERMIT FEES
  14. Appendix AC — RESERVED
  15. Appendix BA — RESERVED
  16. Appendix BB — TINY HOUSES
  17. Appendix BC — RESERVED
  18. Appendix BD — RESERVED
  19. Appendix BE — RADON CONTROL METHODS
  20. Appendix BF — PATIO COVERS
  21. Appendix BG — SOUND TRANSMISSION
  22. Appendix BH — AUTOMATIC VEHICULAR GATES
  23. Appendix BI — LIGHT STRAW-CLAY CONSTRUCTION
  24. ▸ Appendix BJ — STRAWBALE CONSTRUCTION
    Overview
    1. Section BJ101 — GENERAL
    2. Section BJ102 — DEFINITIONS
    3. Section BJ103 — BALES
    4. Section BJ104 — FINISHES
    5. Section BJ105 — STRAWBALE WALLS—GENERAL
    6. Section BJ106 — STRAWBALE WALLS—STRUCTURAL
    7. Section BJ107 — FIRE RESISTANCE
    8. Section BJ108 — THERMAL INSULATION
    9. Section BJ109 — REFERENCED STANDARDS
  25. Appendix BK — COB CONSTRUCTION (MONOLITHIC ADOBE)
  26. Appendix BL — HEMP-LIME (HEMPCRETE) CONSTRUCTION
  27. Appendix BM — 3D-PRINTED BUILDING CONSTRUCTION
  28. Appendix BN — EXTENDED PLATE WALL CONSTRUCTION
  29. Appendix BO — EXISTING BUILDINGS AND STRUCTURES
  30. Appendix CA — RESERVED
  31. Appendix CB — RESERVED
  32. Appendix CC — RESERVED
  33. Appendix CD — RESERVED
  34. Appendix CE — RESERVED
  35. Appendix CF — RESERVED
  36. Appendix CG — NONSEWERED SANITATION SYSTEMS
  37. Appendix CH — PRIVATE SEWAGE DISPOSAL
  38. Appendix CI — SWIMMING POOL SAFETY ACT
  39. Appendix CJ — EMERGENCY HOUSING
  40. Appendix CK — AREAS PROTECTED BY THE FACILITIES OF THE CENTRAL…

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