Permits & Code
Hemp-lime appendix (CRC Appendix BL)
Appendix BL of the California Residential Code sets the rules for hemp-lime (hempcrete) walls in one- and two-family homes. It applies where a jurisdiction adopts it.
| Section | Requirement |
|---|---|
| BL101.1 | Hemp-lime is a non-structural material and wall infill system. One- and two-family dwellings in SDC D0–D2 require an approved engineered design by a registered design professional. |
| BL103.1 | Limited to non-structural solid infill of hemp hurd and binder between or around wall framing, at 12.5–25 lb/ft³. Allows an approved alternative design. |
| BL103.3.1 | One storey above grade; average wall weight no more than 65 psf. |
| BL103.3.2 | Bracing by Method LIB in SDC A–C. |
| BL103.3.4 | At least 3 inches of hemp-lime between the face of framing and the finish. |
| BL103.3.6 | Untreated wood may be in contact with hemp-lime. |
| BL103.4 | Metal in contact with hemp-lime must be stainless or coated (epoxy, oil, bituminous or approved); no water-based paints. |
| BL103.5 | Pipes and wiring in hemp-lime must be sleeved in plastic or coated metal. |
| BL103.6 | Placement: tamped lifts of 4 inches or less, spray, precast blocks in lime mortar, or engineered panels (BL103.6.6). |
| BL103.7 | No water-resistive barriers or vapor retarders on hemp-lime; keep it 8 inches above grade; lime plaster is the air barrier. |
| BL105.1 | Hemp-lime walls have no fire-resistance rating; a rating needs ASTM E119 or UL 263 testing. |
| BL106.1–106.2 | Mass-wall treatment at heat capacity of at least 6 Btu/ft²·°F; R-2.10 per inch at 12.5 pcf down to R-1.20 at 25 pcf. |
Where Appendix BL applies
Appendices in the California codes apply only where the local jurisdiction adopts them. Where Appendix BL has not been adopted, an applicant can ask the building official to approve hemp-lime as an alternative material under CRC R104.11, with test or evaluation reports showing equivalent quality, strength, fire resistance, durability and safety. Check adoption with each city or county building department.
Hempcrete materials and prices
Sources
- 2025 California Residential Code, Appendix BL, Section BL101 General (gocodebook). Checked Oct 17, 2026.
- 2025 CRC Appendix BL, Section BL103 Hemp-Lime Construction (gocodebook; effective Jan 1, 2026). Checked Oct 17, 2026.
- 2025 CRC Appendix BL, Section BL105 Fire Resistance. Checked Oct 17, 2026.
- 2025 CRC Appendix BL, Section BL106 Thermal Performance. Checked Oct 17, 2026.
- 2024 International Residential Code, Appendix BL (ICC). Checked Oct 17, 2026.
- 2025 CRC Section R104, duties and powers of the building official (alternative materials, R104.11). Checked Oct 17, 2026.
- FEMA P-2192 Seismic Design Category maps for the 2024 IRC (July 2024). Checked Oct 17, 2026.
Last updated Oct 18, 2026. Each source above was checked on the date shown.