Section AS105

AS105.1 General.¶

Strawbale walls shall be designed and constructed in accordance with this section and with Figures AS105.1(1) through AS105.1(4) or an approved alternative design. Strawbale structural walls shall be in accordance with the additional requirements of Section AS106.

AS105.2 Building limitations and requirements for use of strawbale nonstructural walls.¶

strawbale nonstructural walls. Buildings using strawbale nonstructural walls shall be subject to the following limitations and requirements:

Number of stories: not more than one, except that two stories shall be allowed with an approved engineered design.

TABLE AS105.4 OUT-OF-PLANE RESISTANCE METHODS AND UNRESTRAINED WALL DIMENSION LIMITS

METHOD OF OUT-OF-PLANE LOAD RESISTANCEa	FOR ULTIMATE DESIGN WIND SPEEDS (mph)	FOR SEISMIC DESIGN CATEGORIES	UNRESTRAINED WALL DIMENSIONS, Hb		MESH STAPLE SPACING AT BOUNDARY RESTRAINTS
METHOD OF OUT-OF-PLANE LOAD RESISTANCEa	FOR ULTIMATE DESIGN WIND SPEEDS (mph)	FOR SEISMIC DESIGN CATEGORIES	Absolute limit in feet	Limit based on bale thickness Tc in feet (mm)	Limit based on bale thickness Tc in feet (mm)
Nonplaster finish or unreinforced plaster	130	A, B, C, D0	H 8	H 5_T_	None required
Pins per Section AS105.4.2	130	A, B, C, D0	H 12	H 8_T_	None required
Pins per Section AS105.4.2	140	A, B, C, D0, D1, D2	H 10	H 7_T_	None required
Reinforcedd clay plaster	140	A, B, C, D0, D1, D2	H 10	H 8_T_ 0.5 (H 140_T_ 0.5)	6 inches
Reinforcedd clay plaster	140	A, B, C, D0, D1, D2	10 <H 12	H 8_T_ 0.5 (H 140_T_ 0.5)	4 inchese
Reinforcedd cement, cement-lime, lime or soil-cement plaster	140	A, B, C, D0, D1, D2	H 10	H 9_T_ 0.5 (H 157_T_ 0.5)	6 inches
Reinforcedd cement, cement-lime, lime or soil-cement plaster	155	A, B, C, D0, D1, D2	H 12	H 9_T_ 0.5 (H 157_T_ 0.5)	4 inchese
2x6 load-bearing studsf at max. 6 o.c.	140	A, B, C, D0, D1, D2	_H_g 9	N/A	None required
2x6 load-bearing studsf at max. 4 o.c.	140	A, B, C, D0, D1, D2	_H_g 10	N/A	None required
2x6 load-bearing studsf at max. 2 o.c.	140	A, B, C, D0, D1, D2	_H_g 12	N/A	None required
2x4 load-bearing studsf at max. 2 o.c.	140	A, B, C, D0, D1, D2	_H_g 10	N/A	None required
2x6 nonload-bearing studsf at max. 6 o.c.	140	A, B, C, D0, D1, D2	_H_g 12	N/A	None required

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s. N/A = Not Applicable a. Finishes applied to both sides of stacked bales. Where different finishes are used on opposite sides of a wall, the more restrictive requirements shall apply. b. H = Stacked bale height in feet (mm) between sill plate and top plate or other approved horizontal restraint, or the horizontal distance in feet (mm) between

approved vertical restraints. For load-bearing walls, H refers to vertical height only. c. T = Bale thickness in feet (mm). d. Plaster reinforcement shall be any mesh allowed in Table AS106.16 for the matching plaster type, and with staple spacing in accordance with this table. Mesh

shall be installed in accordance with Section AS106.9. e. Sill plate attachment shall be with ⁵ /8-inch anchor bolts or approved equivalent at not more than 48 inches on center where staple spacing is required to be 4

inches. f. Bales shall be attached to the studs by an approved method. Horizontal framing and attachment at top and bottom of studs shall be in accordance with Section

R602 or an approved alternative. Table R602.7(1) shall be used to determine the top framing member where load-bearing stud spacing exceeds 24 inches o.c. g. H is vertical height only.

612 2019 CALIFORNIA RESIDENTIAL CODE

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Building height: not more than 25 feet (7620 mm), except that greater heights shall be allowed with an approved engineered design.
Wall height: in accordance with Table AS105.4.
Braced wall panel lengths: in accordance with Section R602.10.3, with the additional requirements that Table R602.10.3(3) shall apply to all buildings in Seismic Design Category C, and the minimum total length of braced wall panels in Table R602.10.3(3) shall be increased by 60 percent for buildings in Seismic Design Categories C, D0, D1 and D2.

AS105.3 Sill plates.¶

Sill plates shall be installed in accordance with Figure AS105.1(1) or AS105.1(2). Sill plates shall support and be flush with each face of the straw bales above and shall be of naturally durable or preservative-treated wood where required by this code. Sill plates shall be not less than nominal 2 inches by 4 inches (51 mm by 102 mm) with anchoring complying with Section R403.1.6 and the additional requirements of Tables AS105.4 and AS106.6(1), where applicable.

AS105.3.1 Exterior sill plate flashing. Exterior sill plates shall receive flashing across the plate to slab or foundation joints.

AS105.4 Out-of-plane resistance methods and unre-strained wall dimension limits.¶

strained wall dimension limits. Strawbale walls shall employ a method of out-of-plane load resistance in accordance with Table AS105.4, and comply with its associated limits and requirements.

AS105.4.1 Determination of out-of-plane loading. Outof-plane loading for the use of Table AS105.4 shall be in terms of the ultimate design wind speed and seismic design category as determined in accordance with Sections R301.2.1 and R301.2.2.

AS105.4.2 Pins. Pins used for out-of-plane resistance shall comply with the following or shall be in accordance with an approved engineered design. Pins shall be external, internal or a combination of the two.

Pins shall be ¹ /2-inch-diameter (12.7 mm) steel, ³ /4inch-diameter (19.1 mm) wood or ¹ /2-inch-diameter (12.7 mm) bamboo.
External pins shall be installed vertically on both sides of the wall at a spacing of not more than 24 inches (610 mm) on center. External pins shall have full lateral bearing on the sill plate and the top plate or roof-bearing element, and shall be tightly tied through the wall to an opposing pin with ties spaced not more than 32 inches (813 mm) apart and not more than 8 inches (203 mm) from each end of the pins.
Internal pins shall be installed vertically within the center third of the bales, at spacing of not more than 24 inches (610 mm) and shall extend from top course to bottom course. The bottom course shall be connected to its support and the top course shall be connected to the roof- or floor-bearing member above with pins or other approved means. Internal pins shall be continuous or shall overlap through not less than one bale course.

STRAWBALE CONSTRUCTION

AS105.5 Connection of light-framed walls to strawbale walls.¶

walls. Light-framed walls perpendicular to, or at an angle to a strawbale wall assembly, shall be fastened to the bottom and top wood members of the strawbale wall in accordance with requirements for wood or cold-formed steel light-framed walls in this code, or the abutting stud shall be connected to alternating strawbale courses with a ¹ /2-inch diameter (12.7 mm) steel, ³ /4-inch-diameter (19.1 mm) wood or ⁵ /8-inchdiameter (15.9 mm) bamboo dowel, with not less than 8-inch (203 mm) penetration.

AS105.6 Moisture control.¶

Strawbale walls shall be protected from moisture intrusion and damage in accordance with Sections AS105.6.1 through AS105.6.9.

AS105.6.1 Water-resistant barriers and vapor perme- ance ratings. Plastered bale walls shall be constructed without any membrane barrier between straw and plaster to facilitate transpiration of moisture from the bales, and to secure a structural bond between straw and plaster, except as permitted or required elsewhere in this appendix. Where a water-resistant barrier is placed behind an exterior finish, it shall have a vapor permeance rating of not less than 5 perms, except as permitted or required elsewhere in this appendix.

AS105.6.2 Vapor retarders. Wall finishes shall have an equivalent vapor permeance rating of a Class III vapor retarder on the interior side of exterior strawbale walls in Climate Zones 14 and 16, as referenced in the California Energy Code . Bales in walls enclosing showers or steam rooms shall be protected on the interior side by a Class I or Class II vapor retarder.

AS105.6.3 Penetrations in exterior strawbale walls. Penetrations in exterior strawbale walls shall be sealed with an approved sealant or gasket on the exterior side of the wall in all climate zones, and on the interior side of the wall in Climate Zones 14 and 16, as referenced in the Cal- ifornia Energy Code.

AS105.6.4 Horizontal surfaces. Bale walls and other bale elements shall be provided with a water-resistant barrier at weather-exposed horizontal surfaces. The water-resistant barrier shall be of a material and installation that will prevent water from entering the wall system. Horizontal surfaces shall include exterior window sills, sills at exterior niches and buttresses. Horizontal surfaces shall be sloped not less than 1 unit vertical in 12 units horizontal (8-percent slope) and shall drain away from bale walls and elements. Where the water-resistant barrier is below the finish material, it shall be sloped not less than 1 unit vertical in 12 units horizontal (8-percent slope) and shall drain to the outside surface of the bale wall’s vertical finish.

AS105.6.5 Separation of bales and concrete. A sheet or liquid-applied Class II vapor retarder shall be installed between bales and supporting concrete or masonry. The bales shall be separated from the vapor retarder by not less than ³ /4 inch (19.1 mm), and that space shall be filled with an insulating material such as wood or rigid insulation, or a material that allows vapor dispersion such as gravel, or other approved insulating or vapor dispersion material. Sill plates shall be installed at this interface in accordance

ing concrete or masonry. The bales shall be separated from the vapor retarder by not less than ³ /4 inch (19.1 mm), and that space shall be filled with an insulating material such as wood or rigid insulation, or a material that allows vapor dispersion such as gravel, or other approved insulating or vapor dispersion material. Sill plates shall be installed at this interface in accordance

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STRAWBALE CONSTRUCTION

with Section AS105.3. Where bales abut a concrete or masonry wall that retains earth, a Class II vapor retarder shall be provided between such wall and the bales.

AS105.6.6 Separation of bales and earth. Bales shall be separated from earth by not less than 8 inches (203 mm).

AS105.6.7 Separation of exterior plaster and earth. Exterior plaster applied to straw bales shall be located not less than 6 inches (102 mm) above earth or 3 inches (51 mm) above paved areas.

AS105.6.8 Separation of wood and plaster. Where wood framing or wood sheathing occurs at the exterior face of strawbale walls, such wood surfaces shall be separated from exterior plaster with two layers of Grade D paper, No. 15 asphalt felt or other approved material in accordance with Section R703.7.3.

Exceptions:

Where the wood is preservative treated or naturally durable and is not greater than 1 ¹ /2 inches (38 mm) in width.
Clay plaster shall not be required to be separated from untreated wood that is not greater than 1 ¹ /2 inches (38 mm) in width.

AS105.6.9 Separation of exterior plaster and founda- tion. Exterior plaster shall be separated from the building foundation with a moisture barrier.

AS105.7 Inspections.¶

The building official shall inspect the following aspects of strawbale construction in accordance with Section R109.1:

Sill plate anchors, as part of and in accordance with Section R109.1.1.
Mesh placement and attachment, where mesh is required by this appendix.
Pins, where required by and in accordance with Section AS105.4.

AS105.8 Voids and stuffing.¶

Voids between bales and between bales and framing members shall not exceed 4 inches (102 mm) in width, and such voids shall be tightly stuffed with flakes, loose straw or straw-clay before application of finish.