CRC · California Residential Code
Roof sheathing, diaphragms and blocking
This hub summarizes CRC rules for roof sheathing, diaphragm construction and edge blocking—what materials, fastening, lengths and connections are required to transfer lateral loads.
Last reviewed: July 6, 2026
Overview
This hub covers CRC requirements for roof sheathing materials and fasteners, the design and attachment of roof and ceiling diaphragms, and the blocking needed to transfer lateral forces (wind and seismic) into the vertical resisting elements. Key diaphragm provisions are found in CRC § R804.3.7 and its subsections for ceiling and roof diaphragms (see § R804.3.7.1 and § R804.3.7.2) which set minimum sheathing types, diaphragm lengths, blocking and fastening rules .
Compliance attention areas include minimum sheathing thickness and installation (for example, a roof diaphragm requires not less than 3/8‑inch wood structural panel sheathing that complies with Section R803), diaphragm edge blocking and fastener spacing (adjustments to required diaphragm lengths are allowed when panel edges are blocked or when closer edge fastener spacing is used), and the roof tie‑down/load‑path connections to walls and foundations as required elsewhere in Chapter R804 .
Definitions and intent—what a diaphragm is and what “blocked” vs “unblocked” diaphragms mean—are consistent with the model-code diaphragm definition and are used throughout the CRC and CBC; fastener schedules and special edge‑nailing requirements are given in the fastening tables (see Table R602.3 and related notes) and the roof sheathing notes for high wind or seismic conditions .
In this section
Code references
Grounded in the retrieved California Residential Code — click a citation to read the verbatim passage:
CRC § 0.35 High relevance — show source text
Ceiling diaphragm is composed of1/2-inch gypsum board (min. thickness) secured with screws spaced at 6 inches o.c. at panel edges and 12 inches o.c. infield. Use No. 8
screws (min.) where framing members have a designation thickness of 54 mils or less and No. 10 screws (min.) where framing members have a designation thickness greater
than 54 mils.
b. Maximum aspect ratio (length/width) of diaphragms is 2:1.
c. Building width is in the direction of horizontal framing members supported by the wall studs.
d. Required diaphragm lengths are to be provided at each end of the structure.
e. Multiplying required diaphragm lengths by 0.35 is permitted if all panel edges are blocked.
f. Multiplying required diaphragm lengths by 0.9 is permitted if all panel edges are secured with screws spaced at 4 inches o.c.
g. To determine the minimum diaphragm length for buildings with ceiling heights of 9 feet or 10 feet values in this table shall be multiplied by 1.15.|FIGURE R804.3.7.1(1)—CEILING DIAPHRAGM TO GABLE ENDWALL DETAIL
CEILING JOISTS
FLAT STUD OR TRACK BLOCKING AT 48 IN. O.C. AT FIRST TWO JOIST SPACES
3 NO. 8 SCREWS AT EACH STUD
STUD BLOCKING AT CEILING ELEVATION
GABLE
ENDWALL
STUDS
For SI: 1 inch = 25.4 mm.
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FIGURE R804.3.7.1(2)—CEILING DIAPHRAGM TO SIDEWALL DETAIL
ROOF-CEILING CONSTRUCTION
ROOF RAFTER (OR TRUSS TOP CHORD)
CEILING JOIST (OR TRUSS BOTTOM CHORD)
WOOD STRUCTURAL
PANEL OR GYPSUM
BOARD DIAPHRAGM
350T125-33 TRACK
ROOF SHEATHING
ROOF BLOCKING
NO. 8 SCREWS AT 6 IN. O.C.
STRUCTURAL WALL
For SI: 1 inch = 25.4 mm.
R804.3.7.2 Roof diaphragm. A roof diaphragm shall be provided by attaching not less than [3] / 8 -inch (9.5 mm) wood structural panel that complies with Section R803 to roof rafters or truss top chords in accordance with Table R804.3. Buildings with 3:1 or larger plan aspect ratio and with roof rafter slope (pitch) of 9:12 or larger shall have the roof rafters and ceiling joists blocked in accordance with Figure R804.3.7.2.
FIGURE R804.3.7.2—ROOF BLOCKING DETAIL
BE ATTACHED TO OUTSIDE FACE OF SHEATHING OR PREFERABLY DIRECTLY TO TRACK FLANGE PRIOR TO SHEATHING PLACEMENT AS SHOWN
For SI: 1 mil = 0.0254 mm, 1 inch = 25.4 mm, 1 foot = 304.8 mm.
2025 CALIFORNIA RESIDENTIAL CODE 8-43
CRC § 3.5 High relevance — show source text
FIGURE R804.3.5(1)—ROOF OR CEILING OPENING
For SI: 1 foot = 304.8 mm.
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ROOF-CEILING CONSTRUCTION
FIGURE R804.3.5(2)—HEADER TO TRIMMER CONNECTION
MINIMUM 2 IN. × 2 IN. CLIP ANGLE WITH 4 NO. 8 SCREWS THROUGH EACH LEG, BOTH SIDES OF CONNECTION
For SI: 1 inch = 25.4 mm.
R804.3.6 Roof trusses. Cold-formed steel trusses shall be designed and installed in accordance with AISI S230, Section F6. In the absence of specific bracing requirements, trusses shall be braced in accordance with accepted industry practices, such as the SBCA Cold-Formed Steel Building Component Safety Information (CFSBCSI) Guide to Good Practice for Handling, Installing & Bracing of Cold-Formed Steel Trusses. Trusses shall be connected to the top track of the load-bearing wall in accordance with Table R804.3, either with the required number of No. 10 screws applied through the flange of the truss or by using a 54-mil (1.37 mm) clip angle with the required number of No. 10 screws in each leg.
R804.3.7 Ceiling and roof diaphragms. Ceiling and roof diaphragms shall be in accordance with this section. R804.3.7.1 Ceiling diaphragms. At gable endwalls a ceiling diaphragm shall be provided by attaching a minimum [1] / 2 -inch (12.7 mm) gypsum board or a minimum [3] / 8 -inch (9.5 mm) wood structural panel sheathing, that complies with Section R803, to the bottom of ceiling joists or roof trusses and connected to wall framing in accordance with Figures R804.3.7.1(1) and R804.3.7.1(2), unless studs are designed as full height without bracing at the ceiling. Flat blocking shall consist of C-shaped or track section with a minimum thickness of 33 mils (0.84 mm). For a gypsum board sheathed ceiling, the diaphragm length shall be in accordance with Table R804.3.7.1. For a wood structural panel sheathed ceiling, the diaphragm length shall be not less than 12 feet (3658 mm) for building widths less than 36 feet (10 973 mm), or not less than 14 feet (4267 mm) for building widths greater than or equal to 36 feet (10 973 mm).
The ceiling diaphragm shall be secured with screws spaced at a maximum 6 inches (152 mm) o.c. at panel edges and a maximum 12 inches (305 mm) o.c. in the field. The required lengths in Table R804.3.7.1 for gypsum board sheathed ceiling diaphragms shall be permitted to be multiplied by 0.35 if all panel edges are blocked. Multiplying the required lengths in Table R804.3.7.1 for gypsum board sheathed ceiling diaphragms by 0.9 shall be permitted if all panel edges are secured with screws spaced at 4 inches (102 mm) o.c.
2025 CALIFORNIA RESIDENTIAL CODE 8-41
CRC § 3.7.1 High relevance — show source text
FIGURE R804.3.7.1(2)—CEILING DIAPHRAGM TO SIDEWALL DETAIL
ROOF-CEILING CONSTRUCTION
ROOF RAFTER (OR TRUSS TOP CHORD)
CEILING JOIST (OR TRUSS BOTTOM CHORD)
WOOD STRUCTURAL
PANEL OR GYPSUM
BOARD DIAPHRAGM
350T125-33 TRACK
ROOF SHEATHING
ROOF BLOCKING
NO. 8 SCREWS AT 6 IN. O.C.
STRUCTURAL WALL
For SI: 1 inch = 25.4 mm.
R804.3.7.2 Roof diaphragm. A roof diaphragm shall be provided by attaching not less than [3] / 8 -inch (9.5 mm) wood structural panel that complies with Section R803 to roof rafters or truss top chords in accordance with Table R804.3. Buildings with 3:1 or larger plan aspect ratio and with roof rafter slope (pitch) of 9:12 or larger shall have the roof rafters and ceiling joists blocked in accordance with Figure R804.3.7.2.
FIGURE R804.3.7.2—ROOF BLOCKING DETAIL
BE ATTACHED TO OUTSIDE FACE OF SHEATHING OR PREFERABLY DIRECTLY TO TRACK FLANGE PRIOR TO SHEATHING PLACEMENT AS SHOWN
For SI: 1 mil = 0.0254 mm, 1 inch = 25.4 mm, 1 foot = 304.8 mm.
2025 CALIFORNIA RESIDENTIAL CODE 8-43
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ROOF-CEILING CONSTRUCTION
R804.3.8 Roof tie-down. Roof assemblies shall be connected to walls below in accordance with Table R804.3. A continuous load path shall be provided to transfer uplift loads to the foundation.
SECTION R805—CEILING FINISHES
R805.1 Ceiling installation. Ceilings shall be installed in accordance with the requirements for interior wall finishes as provided in Sections R702.1 through R702.6.
SECTION R806—ROOF VENTILATION
Note: The IECC climate zones used by this section differ from those used by the California Energy Code to determine applicability of energy efficiency measures. Comparison of IECC and California Energy Code climate zones is shown in Table R702.7.3.
R806.1 Ventilation required. Enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters shall have cross ventilation for each separate space by ventilating openings protected against the entrance of rain or snow. Ventilation openings shall have a least dimension of [1] / 16 inch (1.6 mm) minimum and [1] / 4 inch (6.4 mm) maximum. Ventilation openings having a least dimension larger than [1] / 4 inch (6.4 mm) shall be provided with corrosion-resistant wire cloth screening, hardware cloth, perforated vinyl or similar material with openings having a least dimension of [1] / 16 inch (1.6 mm) minimum and [1] / 4 inch (6.4 mm) maximum. Openings in roof framing members shall conform to the requirements of Section R802.7.
CRC § 12.2. High relevance — show source text
Note: A full bed joint must be provided. Cells containing vertical bars are to be filled to the top of wall and provide inspection opening as shown on detail “A.” Horizontal bars are to be laid as shown on detail “B.” Lintel bars are to be laid as shown on Section C.
R606.12 Seismic requirements. The seismic requirements of this section shall apply to the design of masonry and the construction of masonry building elements located in Seismic Design Category D 0, D 1 or D 2 . Townhouses in Seismic Design Category C shall comply with the requirements of Section R606.12.2. These requirements shall not apply to glass unit masonry conforming to Section R607, anchored masonry veneer conforming to Section R703.8 or adhered masonry veneer conforming to Section R703.12.
R606.12.1 General. Masonry structures and masonry elements shall comply with the requirements of Sections R606.12.2 through R606.12.4 based on the seismic design category established in Table R301.2.1(1). Masonry structures and masonry elements shall comply with the requirements of Section R606.12 and Figures R606.11(1), R606.11(2) and R606.11(3) or shall be designed in accordance with TMS 402 or TMS 403.
R606.12.1.1 Floor and roof diaphragm construction. Floor and roof diaphragms shall be constructed of wood structural panels attached to wood framing in accordance with Table R602.3(1) or to cold-formed steel floor framing in accordance with Table R505.3.1(2) or to cold-formed steel roof framing in accordance with Table R804.3. Additionally, sheathing panel edges
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WALL CONSTRUCTION
perpendicular to framing members shall be backed by blocking, and sheathing shall be connected to the blocking with fasteners at the edge spacing. For Seismic Design Categories C, D 0, D 1 and D 2, where the width-to-thickness dimension of the diaphragm exceeds 2-to-1, edge spacing of fasteners shall be 4 inches (102 mm) on center.
R606.12.2 Seismic Design Category C. Townhouses located in Seismic Design Category C shall comply with the requirements of this section.
R606.12.2.1 Minimum length of wall without openings. Table R606.12.2.1 shall be used to determine the minimum required solid wall length without openings at each masonry exterior wall. The provided percentage of solid wall length shall include only those wall segments that are 3 feet (914 mm) or longer. The maximum clear distance between wall segments included in determining the solid wall length shall not exceed 18 feet (5486 mm). Shear wall segments required to meet the minimum wall length shall be in accordance with Section R606.12.2.2.3.
CRC § 12.1.1 High relevance — show source text
R606.12.1.1 Floor and roof diaphragm construction. Floor and roof diaphragms shall be constructed of wood structural panels attached to wood framing in accordance with Table R602.3(1) or to cold-formed steel floor framing in accordance with Table R505.3.1(2) or to cold-formed steel roof framing in accordance with Table R804.3. Additionally, sheathing panel edges
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WALL CONSTRUCTION
perpendicular to framing members shall be backed by blocking, and sheathing shall be connected to the blocking with fasteners at the edge spacing. For Seismic Design Categories C, D 0, D 1 and D 2, where the width-to-thickness dimension of the diaphragm exceeds 2-to-1, edge spacing of fasteners shall be 4 inches (102 mm) on center.
R606.12.2 Seismic Design Category C. Townhouses located in Seismic Design Category C shall comply with the requirements of this section.
R606.12.2.1 Minimum length of wall without openings. Table R606.12.2.1 shall be used to determine the minimum required solid wall length without openings at each masonry exterior wall. The provided percentage of solid wall length shall include only those wall segments that are 3 feet (914 mm) or longer. The maximum clear distance between wall segments included in determining the solid wall length shall not exceed 18 feet (5486 mm). Shear wall segments required to meet the minimum wall length shall be in accordance with Section R606.12.2.2.3.
TABLE R606.12.2.1—MINIMUM SOLID WALL LENGTH ALONG EXTERIOR WALL LINES Col2 Col3 Col4 ** SESIMIC**
DESIGN CATEGORY** MINIMUM SOLID WALL LENGTH**
(percent)a** MINIMUM SOLID WALL LENGTH**
(percent)a** MINIMUM SOLID WALL LENGTH**
(percent)a** SESIMIC**
DESIGN CATEGORY** One story or**
top story of two story** Wall supporting**
light-frame second story and roof** Wall supporting**
masonry second story and roofTownhouses in C 20 25 35 D0 or D1 25 NP NP D2 30 NP NP NP = Not Permitted, except with design in accordance with the_California Building Code_.
a. For all walls, the minimum required length of solid walls shall be based on the table percent multiplied by the dimension, parallel to the wall direction under consideration, of
a rectangle inscribing the overall building plan.NP = Not Permitted, except with design in accordance with the_California Building Code_.
a. For all walls, the minimum required length of solid walls shall be based on the table percent multiplied by the dimension, parallel to the wall direction under consideration, of
a rectangle inscribing the overall building plan.NP = Not Permitted, except with design in accordance with the_California Building Code_.
a.CRC § 10.8.2 Medium relevance — show source text
Exception: Where the outside edge of truss vertical web members aligns with the outside face of the wall studs below, wood structural panel sheathing extending above the top plate as shown in Figure R602.10.8.2(3) shall be permitted to be fastened to each truss web with three-8d nails (2 [1] / 2 inches × 0.131 inch) and blocking between the trusses shall not be required. 2. For Seismic Design Categories D 0, D 1 and D 2, where the distance from the top of the braced wall panel to the top of the rafters or roof trusses is 15 [1] / 4 inches (387 mm) or less, blocking between rafters or roof trusses shall be provided above the braced wall panel in accordance with Figure R602.10.8.2(1). 3. Where the distance from the top of the braced wall panel to the top of rafters or roof trusses exceeds 15 [1] / 4 inches (387 mm), the top plates of the braced wall panel shall be connected to perpendicular rafters or roof trusses above in accordance with one or more of the following methods: 3.1. Soffit blocking panels constructed in accordance with Figure R602.10.8.2(2). 3.2. Vertical blocking panels constructed in accordance with Figure R602.10.8.2(3). 3.3. Blocking panels provided by the roof truss manufacturer and designed in accordance with Section R802. 3.4. Blocking, blocking panels or other methods of lateral load transfer designed in accordance with the AWC
FIGURE R602.10.8.2(1)—BRACED WALL PANEL CONNECTION TO PERPENDICULAR RAFTERS
SOLID BLOCKING BETWEEN RAFTERS ATTACHED TO TOP PLATES WITH 8d @ 6 ″ O.C. ALONG LENGTH OF BRACED WALL PANEL
For SI: 1 inch = 25.4 mm.
2025 CALIFORNIA RESIDENTIAL CODE 6-47
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WALL CONSTRUCTION
FIGURE R602.10.8.2(2)—BRACED WALL PANEL CONNECTION OPTION TO PERPENDICULAR RAFTERS OR ROOF TRUSSES
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm. a. Methods of bracing shall be as described in Section R602.10.4.
FIGURE R602.10.8.2(3)—BRACED WALL PANEL CONNECTION OPTION TO PERPENDICULAR RAFTERS OR ROOF TRUSSES
WHERE AIR GAP AT TOP IS NOT USED, CENTER W/3 AVAILABLE FOR VENT HOLES
Col1 Col2 Col3 Col4 Col5 W Col7 Col8 Col9 Col10 Col11 W/3ROOF SHEATHING Col2 Col3 Col4 Col5 Col6 Col7 BRACED WALL
PANEL
2x
BLK’G
VENTING
A
BRACING
a
EDGE NAILING PER
TABLE R602.CRC § 0.84 Medium relevance — show source text
Flat blocking shall consist of C-shaped or track section with a minimum thickness of 33 mils (0.84 mm). For a gypsum board sheathed ceiling, the diaphragm length shall be in accordance with Table R804.3.7.1. For a wood structural panel sheathed ceiling, the diaphragm length shall be not less than 12 feet (3658 mm) for building widths less than 36 feet (10 973 mm), or not less than 14 feet (4267 mm) for building widths greater than or equal to 36 feet (10 973 mm).
The ceiling diaphragm shall be secured with screws spaced at a maximum 6 inches (152 mm) o.c. at panel edges and a maximum 12 inches (305 mm) o.c. in the field. The required lengths in Table R804.3.7.1 for gypsum board sheathed ceiling diaphragms shall be permitted to be multiplied by 0.35 if all panel edges are blocked. Multiplying the required lengths in Table R804.3.7.1 for gypsum board sheathed ceiling diaphragms by 0.9 shall be permitted if all panel edges are secured with screws spaced at 4 inches (102 mm) o.c.
2025 CALIFORNIA RESIDENTIAL CODE 8-41
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ROOF-CEILING CONSTRUCTION
TABLE R804.3.7.1—REQUIRED LENGTHS FOR CEILING DIAPHRAGMS AT
GABLE ENDWALLS GYPSUM BOARD SHEATHED, CEILING HEIGHT = 8 FEETa, b, c, d, e, f, gCol2 Col3 Col4 Col5 Col6 Col7 Col8 ** EXPOSURE CATEGORY** ** EXPOSURE CATEGORY** ** ULTIMATE DESIGN WIND SPEED (mph)** ** ULTIMATE DESIGN WIND SPEED (mph)** ** ULTIMATE DESIGN WIND SPEED (mph)** ** ULTIMATE DESIGN WIND SPEED (mph)** ** ULTIMATE DESIGN WIND SPEED (mph)** ** ULTIMATE DESIGN WIND SPEED (mph)** ** B** ** B** ** 115** ** 120** ** 130** ** < 140** ** —** ** —** ** C** ** C** ** —** ** —** ** 115** ** 120** ** 130** ** < 140** ** Roof pitch** ** Building endwall width**
(feet)** Minimum diaphragm length**
(feet)** Minimum diaphragm length**
(feet)** Minimum diaphragm length**
(feet)** Minimum diaphragm length**
(feet)3:12 to 6:12 24–28 16 18 24 26 30 34 3:12 to 6:12 > 28–32 20 20 26 32 34 40 3:12 to 6:12 > 32–36 24 26 30 36 42 46 3:12 to 6:12 > 36–40 26 28 36 40 48 52 6:12 to 9:12 > CRC § 0.35 Medium relevance — show source text
Required diaphragm lengths are to be provided at each end of the structure.
e. Multiplying required diaphragm lengths by 0.35 is permitted if all panel edges are blocked.
f. Multiplying required diaphragm lengths by 0.9 is permitted if all panel edges are secured with screws spaced at 4 inches o.c.
g. To determine the minimum diaphragm length for buildings with ceiling heights of 9 feet or 10 feet values in this table shall be multiplied by 1.15.|For SI: 1 inch = 25.4 mm, 1 mile per hour = 0.447 m/s, 1 foot = 304.8 mm, 1 mil = 0.0254 mm.
a. Ceiling diaphragm is composed of1/2-inch gypsum board (min. thickness) secured with screws spaced at 6 inches o.c. at panel edges and 12 inches o.c. infield. Use No. 8
screws (min.) where framing members have a designation thickness of 54 mils or less and No. 10 screws (min.) where framing members have a designation thickness greater
than 54 mils.
b. Maximum aspect ratio (length/width) of diaphragms is 2:1.
c. Building width is in the direction of horizontal framing members supported by the wall studs.
d. Required diaphragm lengths are to be provided at each end of the structure.
e. Multiplying required diaphragm lengths by 0.35 is permitted if all panel edges are blocked.
f. Multiplying required diaphragm lengths by 0.9 is permitted if all panel edges are secured with screws spaced at 4 inches o.c.
g. To determine the minimum diaphragm length for buildings with ceiling heights of 9 feet or 10 feet values in this table shall be multiplied by 1.15.|For SI: 1 inch = 25.4 mm, 1 mile per hour = 0.447 m/s, 1 foot = 304.8 mm, 1 mil = 0.0254 mm.
a. Ceiling diaphragm is composed of1/2-inch gypsum board (min. thickness) secured with screws spaced at 6 inches o.c. at panel edges and 12 inches o.c. infield. Use No. 8
screws (min.) where framing members have a designation thickness of 54 mils or less and No. 10 screws (min.) where framing members have a designation thickness greater
than 54 mils.
b. Maximum aspect ratio (length/width) of diaphragms is 2:1.
c. Building width is in the direction of horizontal framing members supported by the wall studs.
d. Required diaphragm lengths are to be provided at each end of the structure.
e. Multiplying required diaphragm lengths by 0.35 is permitted if all panel edges are blocked.
f. Multiplying required diaphragm lengths by 0.9 is permitted if all panel edges are secured with screws spaced at 4 inches o.c.
g. To determine the minimum diaphragm length for buildings with ceiling heights of 9 feet or 10 feet values in this table shall be multiplied by 1.15.|FIGURE R804.3.7.1(1)—CEILING DIAPHRAGM TO GABLE ENDWALL DETAIL
CEILING JOISTS
FLAT STUD OR TRACK BLOCKING AT 48 IN. O.C. AT FIRST TWO JOIST SPACES
CRC § 25.4 Medium relevance — show source text
Gypsum sheathing shall conform to ASTM C1396 and shall be installed in accordance with ASTM C1280 or GA 253 . Fiberboard sheathing shall conform to ASTM C208.
h. Spacing of fasteners on floor sheathing panel edges applies to panel edges supported by framing members and required blocking and at floor perimeters only. Spacing of fasteners
on roof sheathing panel edges applies to panel edges supported by framing members and required blocking. Blocking of roof or floor sheathing panel edges perpendicular to the
framing members need not be provided except as required by other provisions of this code. Floor perimeter shall be supported by framing members or solid blocking.
i. Where a rafter is fastened to an adjacent parallel ceiling joist in accordance with this schedule, provide two toe nails on one side of the rafter and toe nails from the ceiling joist
to top plate in accordance with this schedule. The toe nail on the opposite side of the rafter shall not be required.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s; 1 ksi = 6.895 MPa.
a. Nails are smooth-common, box or deformed shanks except where otherwise stated. Nails used for framing and sheathing connections are carbon steel and shall have mini-
mum average bending yield strengths as shown: 80 ksi for shank diameter of 0.192 inch (20d common nail), 90 ksi for shank diameters larger than 0.142 inch but not larger than
0.177 inch, and 100 ksi for shank diameters of 0.142 inch or less. Connections using nails and staples of other materials, such as stainless steel, shall be designed by accepted
engineering practice or approved under Section R104.2.2.
b. RSRS-01 is a Roof Sheathing Ring Shank nail meeting the specifications in ASTM F1667.
c. Nails shall be spaced at not more than 6 inches on center at all supports where spans are 48 inches or greater.
d. Four-foot by 8-foot or 4-foot by 9-foot panels shall be applied vertically.
e. Spacing of fasteners not included in this table shall be based on Table R602.3(2).
f. For wood structural panel roof sheathing attached to gable end roof framing and to intermediate supports within 48 inches of roof edges and ridges, nails shall be spaced at 4
inches on center where the ultimate design wind speed is greater than 130 mph in Exposure B or greater than 110 mph in Exposure C. Fastener spacing applies where roof
framing specific gravity is 0.42 or larger. Where roof framing specific gravity is greater than or equal to 0.35 but less than 0.42 in accordance with AWC NDS, fastening of roof
sheathing shall be with RSRS-03 (21/2″ × 0.131″ × 0.281″ head) nails.
g. Gypsum sheathing shall conform to ASTM C1396 and shall be installed in accordance with ASTM C1280 or GA 253 . Fiberboard sheathing shall conform to ASTM C208.
h. Spacing of fasteners on floor sheathing panel edges applies to panel edges supported by framing members and required blocking and at floor perimeters only. Spacing of fasteners
on roof sheathing panel edges applies to panel edges supported by framing members and required blocking.CRC § 2.1 Medium relevance — show source text
R602.3 Design and construction. Exterior walls of wood-frame construction shall be designed and constructed in accordance with the provisions of this chapter and Figures R602.3(1) and R602.3(2), or in accordance with AWC NDS. Components of exterior walls shall be fastened in accordance with Tables R602.3(1) through R602.3(4). Wall sheathing shall be fastened directly to framing members and, where placed on the exterior side of an exterior wall, shall be capable of resisting the wind pressures listed in Table R301.2.1(1) adjusted for height and exposure using Table R301.2.1(2) and shall conform to the requirements of Table R602.3(3). Wall sheathing used only for exterior wall covering purposes shall comply with Section R703.
2025 CALIFORNIA RESIDENTIAL CODE 6-3
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WALL CONSTRUCTION
Studs shall be continuous from support at the sole plate to a support at the top plate to resist loads perpendicular to the wall. The support shall be a foundation or floor, ceiling or roof diaphragm or shall be designed in accordance with accepted engineering practice.
Exception: Jack studs, trimmer studs and cripple studs at openings in walls that comply with Tables R602.7(1) and R602.7(2).
TABLE R602.3(1)—FASTENING SCHEDULE Col2 Col3 Col4 ITEM DESCRIPTION OF BUILDING ELEMENTS NUMBER AND TYPE OF FASTENERa, b, c SPACING AND LOCATION Roof Roof Roof Roof 1 Blocking between ceiling joists, rafters or trusses to
top plate or other framing below4-8d box (21/2″ × 0.113″); or
3-8d common (21/2″ × 0.131″); or
3-10d box (3″ × 0.128″); or
3-3″ × 0.131″ nailsToe nail 1 Blocking between rafters or truss not at the wall
top plates, to rafter or truss2-8d common (21/2″ × 0.131″); or
2-3″ × 0.131″ nailsEach end toe nail 1 Blocking between rafters or truss not at the wall
top plates, to rafter or truss2-16d common (31/2″ × 0.162″); or
3-3″ × 0.131″ nailsEnd nail 1 Flat blocking to truss and web filler 16d common (31/2″ × 0.162″); or
3″ × 0.131″ nails6″ o.c. face nail 2 Ceiling joists to top plate 4-8d box (21/2″ × 0.113″); or
3-8d common (21/2″ × 0.131″); or
3-10d box (3″ × 0.128″); or
3-3″ × 0.131″ nailsPer joist, toe nail 3 Ceiling joist not attached to parallel rafter, laps
over partitions [see Section R802.5.CRC § 0.42 Medium relevance — show source text
Spacing of fasteners not included in this table shall be based on Table R602.3(2).
f. For wood structural panel roof sheathing attached to gable end roof framing and to intermediate supports within 48 inches of roof edges and ridges, nails shall be spaced at 4
inches on center where the ultimate design wind speed is greater than 130 mph in Exposure B or greater than 110 mph in Exposure C. Fastener spacing applies where roof
framing specific gravity is 0.42 or larger. Where roof framing specific gravity is greater than or equal to 0.35 but less than 0.42 in accordance with AWC NDS, fastening of roof
sheathing shall be with RSRS-03 (21/2″ × 0.131″ × 0.281″ head) nails.
g. Gypsum sheathing shall conform to ASTM C1396 and shall be installed in accordance with ASTM C1280 or GA 253 . Fiberboard sheathing shall conform to ASTM C208.
h. Spacing of fasteners on floor sheathing panel edges applies to panel edges supported by framing members and required blocking and at floor perimeters only. Spacing of fasteners
on roof sheathing panel edges applies to panel edges supported by framing members and required blocking. Blocking of roof or floor sheathing panel edges perpendicular to the
framing members need not be provided except as required by other provisions of this code. Floor perimeter shall be supported by framing members or solid blocking.
i. Where a rafter is fastened to an adjacent parallel ceiling joist in accordance with this schedule, provide two toe nails on one side of the rafter and toe nails from the ceiling joist
to top plate in accordance with this schedule. The toe nail on the opposite side of the rafter shall not be required.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s; 1 ksi = 6.895 MPa.
a. Nails are smooth-common, box or deformed shanks except where otherwise stated. Nails used for framing and sheathing connections are carbon steel and shall have mini-
mum average bending yield strengths as shown: 80 ksi for shank diameter of 0.192 inch (20d common nail), 90 ksi for shank diameters larger than 0.142 inch but not larger than
0.177 inch, and 100 ksi for shank diameters of 0.142 inch or less. Connections using nails and staples of other materials, such as stainless steel, shall be designed by accepted
engineering practice or approved under Section R104.2.2.
b. RSRS-01 is a Roof Sheathing Ring Shank nail meeting the specifications in ASTM F1667.
c. Nails shall be spaced at not more than 6 inches on center at all supports where spans are 48 inches or greater.
d. Four-foot by 8-foot or 4-foot by 9-foot panels shall be applied vertically.
e. Spacing of fasteners not included in this table shall be based on Table R602.3(2).
f. For wood structural panel roof sheathing attached to gable end roof framing and to intermediate supports within 48 inches of roof edges and ridges, nails shall be spaced at 4
inches on center where the ultimate design wind speed is greater than 130 mph in Exposure B or greater than 110 mph in Exposure C. Fastener spacing applies where roof
framing specific gravity is 0.42 or larger.CRC § 0.42 Medium relevance — show source text
RSRS-01 is a Roof Sheathing Ring Shank nail meeting the specifications in ASTM F1667.
c. Nails shall be spaced at not more than 6 inches on center at all supports where spans are 48 inches or greater.
d. Four-foot by 8-foot or 4-foot by 9-foot panels shall be applied vertically.
e. Spacing of fasteners not included in this table shall be based on Table R602.3(2).
f. For wood structural panel roof sheathing attached to gable end roof framing and to intermediate supports within 48 inches of roof edges and ridges, nails shall be spaced at 4
inches on center where the ultimate design wind speed is greater than 130 mph in Exposure B or greater than 110 mph in Exposure C. Fastener spacing applies where roof
framing specific gravity is 0.42 or larger. Where roof framing specific gravity is greater than or equal to 0.35 but less than 0.42 in accordance with AWC NDS, fastening of roof
sheathing shall be with RSRS-03 (21/2″ × 0.131″ × 0.281″ head) nails.
g. Gypsum sheathing shall conform to ASTM C1396 and shall be installed in accordance with ASTM C1280 or GA 253 . Fiberboard sheathing shall conform to ASTM C208.
h. Spacing of fasteners on floor sheathing panel edges applies to panel edges supported by framing members and required blocking and at floor perimeters only. Spacing of fasteners
on roof sheathing panel edges applies to panel edges supported by framing members and required blocking. Blocking of roof or floor sheathing panel edges perpendicular to the
framing members need not be provided except as required by other provisions of this code. Floor perimeter shall be supported by framing members or solid blocking.
i. Where a rafter is fastened to an adjacent parallel ceiling joist in accordance with this schedule, provide two toe nails on one side of the rafter and toe nails from the ceiling joist
to top plate in accordance with this schedule. The toe nail on the opposite side of the rafter shall not be required.|TABLE R602.3(2)—ALTERNATE ATTACHMENTS TO TABLE R602.3(1) Col2 Col3 Col4 ** NOMINAL**
MATERIAL
THICKNESS
(inches)** DESCRIPTIONa, b OF FASTENER AND LENGTH**
(inches)** SPACINGc OF FASTENERS** ** SPACINGc OF FASTENERS** ** NOMINAL**
MATERIAL
THICKNESS
(inches)** DESCRIPTIONa, b OF FASTENER AND LENGTH**
(inches)** Edges**
(inches)** Intermediate**
supports
(inches)** Wood structural panels subfloor, roofg and wall sheathing to framing and particleboard wall sheathing to framingf** ** Wood structural panels subfloor, roofg and wall sheathing to framing and particleboard wall sheathing to framingf** ** Wood structural panels subfloor, roofg and wall sheathing to framing and particleboard wall sheathing to framingf** ** Wood structural panels subfloor, roofg and wall sheathing to framing and particleboard wall sheathing to framingf** Up to1/2 Staple 15 ga.
Frequently asked questions
What minimum sheathing is required for a roof diaphragm?
A roof diaphragm must be provided by attaching not less than 3/8‑inch (9.5 mm) wood structural panel sheathing that complies with Section R803 to rafters or truss top chords per § R804.3.7.2 .
When is blocking required at sheathing panel edges?
Panel edges perpendicular to framing must be backed by blocking where required by code provisions (for example where diaphragm edges do not occur over framing, for transfer at braced wall lines, and in seismic design provisions). Braced wall/top‑plate connections and blocking above braced wall panels are specifically addressed in § R602.10.8.2 and related seismic sections .
Can gypsum board be used as a ceiling diaphragm?
Yes—CRC § R804.3.7.1 permits a ceiling diaphragm formed with 1/2‑inch gypsum board (or 3/8‑inch wood structural panels) and specifies fastening patterns and required diaphragm lengths (with permitted length reductions when edges are blocked or when closer edge screw spacing is used) .
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