BJ107 Fire Resistance — 2025 California Residential Code

Strawbale walls shall not be considered to exhibit a fire-resistance rating, except for walls constructed in accordance with Section BJ107.1.1 or BJ107.1.2. Alternately, fire-resistance ratings of strawbale walls shall be determined in accordance with Section R302.

BJ107.1.1 One-hour-rated clay-plastered wall. One-hour fire-resistance-rated nonload-bearing clay plastered strawbale walls shall comply with all of the following:

1. Bales shall be laid flat or on-edge in a running bond.
2. Bales shall maintain thickness of not less than 18 inches (457 mm).
3. Bales shall have a minimum dry density of 7.25 pounds per cubic foot (116 kg/m [3] ).
4. Gaps shall be stuffed with straw-clay.
5. Clay plaster on each side of the wall shall be not less than 1 inch (25 mm) thick and shall be composed of a mixture of 3 parts clay, 2 parts chopped straw and 6 parts sand, or an alternative approved clay plaster.
6. Plaster application shall be in accordance with Section BJ104.4.3.3 for the number and thickness of coats.

BJ107.1.2 Two-hour-rated cement-plastered wall. Two-hour fire-resistance-rated nonload-bearing cement-plastered strawbale walls shall comply with all of the following:

1. Bales shall be laid flat or on-edge in a running bond.
2. Bales shall maintain a thickness of not less than 14 inches (356 mm).
3. Bales shall have a minimum dry density of 7.25 pounds per cubic foot (116 kg/m [3] ).
4. Gaps shall be stuffed with straw-clay.
5. A single section of 1/2-inch (38 mm) by 17-gage galvanized woven wire mesh shall be attached to wood members with 1 1/2-inch (38 mm) staples at 6 inches (152 mm) on center. 9 gage U-pins with not less than 8-inch (203 mm) legs shall be installed at 18 inches (457 mm) on center to fasten the mesh to the bales.
6. Cement plaster on each side of the wall shall be not less than 1 inch (25 mm) thick.
7. Plaster application shall be in accordance with Section BJ104.4.9 for the number and thickness of coats.

Openings and penetrations in bale walls required to have a fire-resistance rating shall satisfy the same requirements for openings and penetrations as prescribed in this code.

Strawbale surfaces adjacent to fireplaces or chimneys shall be finished with not less than 3/8-inch-thick (10 mm) plaster of any type permitted by this appendix. Clearance from the face of such plaster to fireplaces and chimneys shall be maintained as required from fireplaces and chimneys to combustibles in Chapter 10, or as required by manufacturer’s instructions, whichever is more restrictive.