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Earlier editions: 20222019

Appendix BL — HEMP-LIME (HEMPCRETE) CONSTRUCTION

BL107 Mechanical Performance — 2025 California Residential Code

California Residential Code (Title 24, Part 2.5) · 2025 edition · updated 2026-10-19 · California

CBSC: official editions, supplements and errata

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

How strong must hemp-lime infill be, and how is it tested?

At least 29 psi compressive strength; prove it to the building official with lab tests of three cured samples before placing infill. You can reuse test results for the same mix on future projects.

Cite as: 2025 California Residential Code (Title 24, Part 2.5) § BL107 · Effective January 1, 2026 · Official source: Building Standards Commission

BL107.1 Hemp-lime infill integrity.

The integrity of hemp-lime infill and its ability to hold a plaster finish shall be demonstrated with a minimum compressive strength of 29 psi (0.2 MPa). Test results from a specific hemp-lime mix shall be permit-ted to be used for multiple projects.

BL107.1.1 Demonstration of compressive strength. The compressive strength of the hemp-lime mix shall be demonstrated to the building official before the placement of hemp-lime infill, with compressive strength tests and an associated report by an approved laboratory tested as follows:

  1. Three samples of the proposed hemp-lime mix shall be placed moist to completely fill a 6-inch by 6-inch by 12-inch (152 mm × 152 mm × 305 mm) form, a 6-inch (152mm) diameter by 12-inch (305 mm) length form, or other approved form, following the application method and procedure that will be used during construction.
  2. Samples shall be removed from the forms within 24 hours after hemp-lime placement or per the binder manufacturer’s specifications.
  3. Samples shall be cured/dried for a minimum of 14 days in indoor ambient conditions before testing.
  4. The opposite faces shall be capped with plaster of paris to achieve smooth and parallel faces, after which the sample shall reach ambient moisture conditions before testing.
  5. The horizontal cross section of the dried sample as tested and the maximum applied load at failure shall be used to calculate the sample’s compressive strength.
  6. The average value of the samples shall be used to determine the mix’s compressive strength.
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▸Contents — California Residential Code (Title 24, Part 2.5)
California Residential Code (Title 24, Part 2.5)

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