CRC · California Residential Code
What are the exposure and installation rules for wood structural panel roof sheathing?
For roof sheathing the CRC requires panels to carry an approved grade mark, to be **exterior exposure** rated if permanently outdoors, and allows **Exposure 1** (interior type with exterior glue) only when the panel is exposed to the underside; fire‑retardant plywood requires approved stress/fastener values. **§ R803.2.1**, **§ R803.2.1.1**, **§ R803.2.1.2**.
Last reviewed: July 6, 2026
What the code requires — 2–4 sentences
Wood structural panel roof sheathing must be manufactured and identified to recognized panel standards and grade marks (DOC PS 1/PS 2 or CSA) and must meet the grades listed in the code tables — see § R803.2.1.
If the panel is intended to be permanently exposed outdoors it must have exterior exposure durability; panels that are exposed only to the underside (attic/soffit exposure) may be the interior type bonded with exterior glue (Exposure 1). § R803.2.1.1.
Fire‑retardant‑treated plywood requires allowable stresses and fastener values developed by an approved investigation and must be graded by an approved agency. § R803.2.1.2.
The single most important rule: if the panel will be in permanent outdoor exposure, use panels rated for exterior exposure durability; if only exposed to the underside (not the weather), Exposure 1 panels are allowed. § R803.2.1.1.
Requirements in detail
Identification and grade (what to buy)
- Panels must conform to DOC PS 1, DOC PS 2, CSA O325 or CSA O437 and be identified for grade, bond classification and performance category by a grade mark or certificate of inspection from an approved agency. § R803.2.1.
- The code requires compliance with the grades specified in Table R503.2.1.1(1) (see the code tables for specific thickness/span/rating combinations). § R803.2.1.
Exposure durability (which panel type to use where)
- Permanently outdoors (weather-exposed) → exterior exposure durability required. § R803.2.1.1.
- Panels exposed to the underside only (i.e., the roof deck is not intended to be weather-exposed from above but the underside is exposed to the attic) → interior type bonded with exterior glue (Exposure 1) is permitted. § R803.2.1.1.
Fire‑retardant‑treated (FRT) plywood rules
- Fire‑retardant‑treated plywood: allowable stresses (including fastener values) must be developed from an approved method of investigation that accounts for expected temperature/humidity, treatment type, and redrying. The FRT plywood must be graded by an approved agency. § R803.2.1.2.
Installation (what the code says about field installation)
The controlling sections listed above focus on identification and exposure. The CRC also contains installation rules you must follow — for example:
- Panel orientation, joint staggering, cantilever limits and allowable spans are specified elsewhere in Section R803 and in the tables referenced by it (see § R803.2.2 and § R803.2.3 for spans and installation rules).
- Fastener types, spacing and special nailing at gable ends/edges are specified in the nailing tables and Table R602.3(2) (see the code tables for exact nail sizes, ring‑shank requirements, and spacing).
Decision‑relevant values (quick reference)
| Item | Value / Rule | Code reference |
|---|---|---|
| Panel standards required | DOC PS 1 / DOC PS 2 / CSA O325 / CSA O437 (identified by grade mark) | § R803.2.1 |
| Permanently exposed outdoors | Exterior exposure durability required | § R803.2.1.1 |
| Underside-exposed roof sheathing | Exposure 1 (interior type bonded with exterior glue) permitted | § R803.2.1.1 |
| Fire‑retardant plywood | Allowable stresses & fastener values must come from approved investigation; FRT plywood must be graded | § R803.2.1.2 |
| Cantilever beyond gable end | Not more than 9 inches (229 mm) unless supported by gable overhang framing | § R803.2.3 |
(For specific panel thicknesses, spans, nail types and spacing consult Table R503.2.1.1(1), Table R602.3(2) and the installation tables in Section R803 — these contain the tabulated fastener sizes, spacing and span limits.)
Exceptions & special cases
- Underside exposure exception: when the sheathing is exposed only to the underside, the code explicitly permits interior type panels identified as Exposure 1; you do not have to use exterior‑exposure panels in that situation. § R803.2.1.1.
- Fire‑retardant‑treated panels are treated differently for design values — you cannot apply untreated panel allowable stresses to FRT plywood; the code requires an approved evaluation to establish allowable stresses and fastener values. § R803.2.1.2.
- Installation details (nail type/spacing, panel orientation, edge blocking, cantilevers greater than 9") are regulated elsewhere in the CRC (e.g., § R803.2.2, § R803.2.3, and referenced tables). If you need those numeric installation rules, consult those specific sections and tables.
Common mistakes
- Using interior‑grade panels (not rated for exterior exposure) where the sheathing will be weather‑exposed — violates § R803.2.1.1.
- Assuming fire‑retardant plywood has the same allowable stresses and nail values as untreated plywood — FRT material requires approved stress values. § R803.2.1.2.
- Failing to verify the grade mark / certificate of inspection on panels — the code requires identification for grade, bond classification and performance. § R803.2.1.
- Ignoring installation tables (spans, nail spacing, ring‑shank requirements) and relying solely on exposure rules — exposure, grade and installation are separate code requirements and all must be satisfied. See § R803.2.2, § R803.2.3, and the nailing tables.
Worked example
Scenario: You are installing 4' × 8' OSB panels as roof sheathing on a simple gable house. The underside of the roof sheathing will be visible from the attic (i.e., underside‑exposed), but the roof deck will be covered with shingles and not permanently weather‑exposed.
- Exposure selection: because the panel is exposed to the underside only, the CRC permits using interior type panels bonded with exterior glue (Exposure 1). Use Exposure 1 panels and confirm the grade mark. § R803.2.1.1 and § R803.2.1.
- Installation notes you must check: confirm allowable spans for the chosen panel thickness and rafter spacing in Table R503.2.1.1(1) or APA E30 (per § R803.2.2), and follow the nailing pattern, nail type and spacing from the applicable nailing table (Table R602.3(2) or the roof sheathing schedule). § R803.2.2 and R803.2.3.
- Gable overhang / cantilever: if any panel cantilevers beyond the gable endwall, ensure it does not exceed 9 inches unless supported by gable overhang framing. § R803.2.3.
Related provisions
- § R803.2.2 — Allowable spans for wood structural panel roof sheathing (Table R503.2.1.1(1) / APA E30).
- § R803.2.3 — Installation requirements (panel orientation, joint staggering, cantilever limits).
- Table R602.3(2) — Alternate fastener descriptions and spacing referenced by the nailing schedules.
- Table R503.2.1.1(1) and APA E30 — Panel span/grade charts referenced by § R803.2.2.
Code references
Grounded in the retrieved California Residential Code — click a citation to read the verbatim passage:
CRC § 0.42 High 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 § 2.1 High relevance — show source text
R803.2 Wood structural panel sheathing.
R803.2.1 Identification and grade. Wood structural panels shall conform to DOC PS 1, DOC PS 2, CSA O325 or CSA O437, and shall be identified for grade, bond classification and performance category by a grade mark or certificate of inspection issued by an approved agency. Wood structural panels shall comply with the grades specified in Table R503.2.1.1(1).
8-30 2025 CALIFORNIA RESIDENTIAL CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
ROOF-CEILING CONSTRUCTION
R803.2.1.1 Exposure durability. Wood structural panels, when designed to be permanently exposed in outdoor applications, shall be of an exterior exposure durability. Wood structural panel roof sheathing exposed to the underside shall be permitted to be of interior type bonded with exterior glue, identified as Exposure 1.
R803.2.1.2 Fire-retardant-treated plywood. The allowable unit stresses for fire-retardant-treated plywood, including fastener values, shall be developed from an approved method of investigation that considers the effects of anticipated temperature and humidity to which the fire-retardant-treated plywood will be subjected, the type of treatment and redrying process. The fire-retardant-treated plywood shall be graded by an approved agency.
R803.2.2 Allowable spans. The maximum allowable spans for wood structural panel roof sheathing shall not exceed the values set forth in Table R503.2.1.1(1) or APA E30.
R803.2.3 Installation. Wood structural panel used as roof sheathing shall be installed with joints staggered or not staggered in accordance with Table R602.3(1), APA E30 for wood roof framing or with Table R804.3 for cold-formed steel roof framing. Wood structural panel roof sheathing in accordance with Table R503.2.1.1(1) shall not cantilever more than 9 inches (229 mm) beyond the gable endwall unless supported by gable overhang framing.
SECTION R804—COLD-FORMED STEEL ROOF FRAMING
R804.1 General. Elements shall be straight and free of any defects that would significantly affect their structural performance. Coldformed steel roof framing members shall be in accordance with the requirements of this section.
R804.1.1 Applicability limits. The provisions of this section shall control the construction of cold-formed steel roof framing for buildings not greater than 60 feet (18 288 mm) perpendicular to the joist, rafter or truss span, not greater than 40 feet (12 192 mm) in width parallel to the joist span or truss, less than or equal to three stories above grade plane and with roof slopes not less than 3:12 (25-percent slope) or greater than 12:12 (100-percent slope). Cold-formed steel roof framing constructed in accordance with the provisions of this section shall be limited to sites where the ultimate design wind speed is less than 140 miles per hour (63 m/s), Exposure Category B or C, and the ground snow load is less than or equal to 70 pounds per square foot (3350 Pa).
R804.1.1.1 Alternate applications. Cold-formed steel roof and ceiling framing for buildings exceeding the applicability limits of Section R804.1.1 is permitted to be designed and constructed in accordance with AISI S230, subject to the limits therein.
CRC § 8.1.1 High relevance — show source text
Where wood shakes are installed over spaced sheathing and the underside of the shakes are exposed to the attic space, the attic shall be ventilated in accordance with Sections R806.1, R806.2, R806.3 and R806.4. The shakes shall not be backed with materials that will occupy the required air gap space and prevent the free movement of air on the interior side of the spaced sheathing.
R905.8.1.1 Solid sheathing required. In areas where the average daily temperature in January is 25°F (-4°C) or less, wood structural panels or solid lumber sheathing is required on that portion of the roof deck requiring an ice barrier.
R905.8.2 Slope. Wood shakes shall only be used on slopes of 3 units vertical in 12 units horizontal (25-percent slope) or greater.
R905.8.3 Underlayment. Underlayment shall comply with Section R905.1.1.
R905.8.3.1 Ice barrier. Where required, ice barriers shall comply with Section R905.1.2.
R905.8.4 Interlayment. Interlayment shall comply with ASTM D226, Type I.
R905.8.5 Material standards. Wood shakes shall comply with the requirements of Table R905.8.5.
2025 CALIFORNIA RESIDENTIAL CODE 9-13
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
ROOF ASSEMBLIES
TABLE R905.8.5—WOOD SHAKE MATERIAL REQUIREMENTS Col2 Col3 ** MATERIAL** ** MINIMUM GRADES** ** APPLICABLE GRADING RULES** Wood shakes of naturally durable wood 1 Cedar Shake and Shingle Bureau Tapersawn shakes of naturally durable wood 1 or 2 Cedar Shake and Shingle Bureau Preservative-treated shakes and shingles of naturally
durable wood1 Cedar Shake and Shingle Bureau Fire-retardant-treated shakes and shingles of naturally
durable wood1 Cedar Shake and Shingle Bureau Preservative-treated tapersawn shakes of Southern pine
treated in accordance with AWPA Standard U1
(Commodity Specification A, Special Requirement 4.6)1 or 2 Forest Products Laboratory of the Texas Forest Services R905.8.6 Wind resistance of wood shakes. In regions where wind design is required in accordance with Figure R301.2.1.1, Wood shakes shall be installed to resist the component and cladding loads specified in Table R301.2.1(1), adjusted for height and exposure in accordance with Table R301.2.1(2). In regions where wind design is not required in accordance with Figure R301.2.1.1, wood shakes are permitted to be attached in accordance with Section R905.8.8.
R905.8.7 Application. Wood shakes shall be installed in accordance with this chapter and the manufacturer’s installation instructions. Wood shakes shall be laid with a side lap not less than 1 [1] / 2 inches (38 mm) between joints in adjacent courses. Spacing between shakes in the same course shall be [3] / 8 inch to [5] / 8 inch (9.5 mm to 15.9 mm) including tapersawn shakes. Weather exposures for wood shakes shall not exceed those set in Table R905.8.7.
CRC § 0.42 High 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. CRC § 0.35 High relevance — show source text
Where the specific gravity of the wood species used for roof framing 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 unless alternative fastening is designed in accordance with AWC NDS. Where the specific gravity of the wood
species used for roof framing is less than 0.35, fastening of the roof sheathing shall be designed in accordance with AWC NDS.
f. Fastening is only permitted where the basic wind speed,V, is less than or equal to 110 mph and where fastening is to wood framing of a species with specific gravity greater
than or equal to 0.42 in accordance with AWC NDS.
g. Nails and staples are carbon steel meeting the specifications of ASTM F1667. Connections using nails and staples of other materials, such as stainless steel, shall be designed
by acceptable engineering practice or approved under Section 104.2.3.|For SI: 1 inch = 25.4 mm.
a. Nails spaced at 6 inches at intermediate supports where spans are 48 inches or more. For nailing of wood structural panel and particleboard diaphragms and shear walls, refer
to Section 2305. Nails for wall sheathing are permitted to be common, box or casing.
b. Spacing shall be 6 inches on center on the edges and 12 inches on center at intermediate supports for nonstructural applications. Panel supports at 16 inches (20 inches if
strength axis in the long direction of the panel, unless otherwise marked).
c. Where a rafter is fastened to an adjacent parallel ceiling joist in accordance with this schedule and the ceiling joist is fastened to the top plate in accordance with this schedule,
the number of toenails in the rafter shall be permitted to be reduced by one nail.
d. RSRS is a Roof Sheathing Ring Shank nail meeting the specifications in ASTM F1667.
e. Tabulated fastener requirements apply where the basic wind speed,V, is less than 140 mph. 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 basic wind speed,V, is greater than 130 mph in Expo-
sure B or greater than 110 mph in Exposure C. Spacing exceeding 6 inches on center at intermediate supports shall be permitted where the fastening is designed per the AWC
NDS. Where the specific gravity of the wood species used for roof framing 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 unless alternative fastening is designed in accordance with AWC NDS. Where the specific gravity of the wood
species used for roof framing is less than 0.35, fastening of the roof sheathing shall be designed in accordance with AWC NDS.
f. Fastening is only permitted where the basic wind speed,V, is less than or equal to 110 mph and where fastening is to wood framing of a species with specific gravity greater
than or equal to 0.42 in accordance with AWC NDS.
g. Nails and staples are carbon steel meeting the specifications of ASTM F1667.CRC § 104.2.3. High relevance — show source text
Connections using nails and staples of other materials, such as stainless steel, shall be designed
by acceptable engineering practice or approved under Section 104.2.3.|For SI: 1 inch = 25.4 mm.
a. Nails spaced at 6 inches at intermediate supports where spans are 48 inches or more. For nailing of wood structural panel and particleboard diaphragms and shear walls, refer
to Section 2305. Nails for wall sheathing are permitted to be common, box or casing.
b. Spacing shall be 6 inches on center on the edges and 12 inches on center at intermediate supports for nonstructural applications. Panel supports at 16 inches (20 inches if
strength axis in the long direction of the panel, unless otherwise marked).
c. Where a rafter is fastened to an adjacent parallel ceiling joist in accordance with this schedule and the ceiling joist is fastened to the top plate in accordance with this schedule,
the number of toenails in the rafter shall be permitted to be reduced by one nail.
d. RSRS is a Roof Sheathing Ring Shank nail meeting the specifications in ASTM F1667.
e. Tabulated fastener requirements apply where the basic wind speed,V, is less than 140 mph. 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 basic wind speed,V, is greater than 130 mph in Expo-
sure B or greater than 110 mph in Exposure C. Spacing exceeding 6 inches on center at intermediate supports shall be permitted where the fastening is designed per the AWC
NDS. Where the specific gravity of the wood species used for roof framing 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 unless alternative fastening is designed in accordance with AWC NDS. Where the specific gravity of the wood
species used for roof framing is less than 0.35, fastening of the roof sheathing shall be designed in accordance with AWC NDS.
f. Fastening is only permitted where the basic wind speed,V, is less than or equal to 110 mph and where fastening is to wood framing of a species with specific gravity greater
than or equal to 0.42 in accordance with AWC NDS.
g. Nails and staples are carbon steel meeting the specifications of ASTM F1667. Connections using nails and staples of other materials, such as stainless steel, shall be designed
by acceptable engineering practice or approved under Section 104.2.3.|For SI: 1 inch = 25.4 mm.
a. Nails spaced at 6 inches at intermediate supports where spans are 48 inches or more. For nailing of wood structural panel and particleboard diaphragms and shear walls, refer
to Section 2305. Nails for wall sheathing are permitted to be common, box or casing.
b. Spacing shall be 6 inches on center on the edges and 12 inches on center at intermediate supports for nonstructural applications. Panel supports at 16 inches (20 inches if
strength axis in the long direction of the panel, unless otherwise marked).
c.CRC § 6.7 High relevance — show source text
R905.6.7 Flashing. Flashing and counterflashing shall be made with sheet metal. Valley flashing shall be not less than 15 inches (381 mm) wide. Valley and flashing metal shall be a minimum uncoated thickness of 0.0179-inch (0.5 mm) zinc-coated G90. Chimneys, stucco or brick walls shall have not less than two plies of felt for a cap flashing consisting of a 4-inch-wide (102 mm) strip of felt set in plastic cement and extending 1 inch (25 mm) above the first felt and a top coating of plastic cement. The felt shall extend 2 inches (51 mm) over the base flashing.
R905.7 Wood shingles. The installation of wood shingles shall comply with the provisions of this section.
R905.7.1 Sheathing requirements. Wood shingles shall be fastened to wood structural panels, solid lumber sheathing or spaced lumber sheathing. Where spaced lumber sheathing is used, sheathing boards shall be not less than 1-inch by 4-inch (25 mm by 102 mm) nominal dimensions and shall be spaced on centers equal to the weather exposure to coincide with the placement of fasteners. Where 1-inch by 4-inch (25 mm by 102 mm) spaced sheathing is installed at 10 inches (254 mm) or greater, additional 1-inch by 4-inch (25 mm by 102 mm) boards shall be installed between the sheathing boards. Where wood shingles are installed over spaced sheathing and the underside of the shingles are exposed to the attic space, the attic shall be ventilated in accordance with Sections R806.1, R806.2, R806.3 and R806.4. The shingles shall not be backed with materials that will occupy the required air gap space and prevent the free movement of air on the interior side of the spaced sheathing.
R905.7.1.1 Solid sheathing required. In areas where the average daily temperature in January is 25°F (-4°C) or less, wood structural panels or solid lumber sheathing is required on that portion of the roof deck requiring the application of an ice barrier.
R905.7.2 Slope. Wood shingles shall be installed on slopes of 3 units vertical in 12 units horizontal (25-percent slope) or greater.
R905.7.3 Underlayment. Underlayment shall comply with Section R905.1.1.
R905.7.3.1 Ice barrier. Where required, ice barriers shall comply with Section R905.1.2.
R905.7.4 Material standards. Wood shingles shall be of naturally durable wood and comply with the requirements of Table R905.7.4.
TABLE R905.7.4—WOOD SHINGLE MATERIAL REQUIREMENTS Col2 Col3 ** MATERIAL** ** MINIMUM GRADES** ** APPLICABLE GRADING RULES** Wood shingles of naturally durable wood 1, 2 or 3 CSSB CRC § 0.113 High relevance — show source text
or 16 ga.
staple galvanized, 15/8″ long,7/16″ or
1″ crown; or 15/8″ screws, Type W or S|7|7| |Wood structural panels, combination subfloor underlayment to framing|Wood structural panels, combination subfloor underlayment to framing|Wood structural panels, combination subfloor underlayment to framing|Wood structural panels, combination subfloor underlayment to framing|Wood structural panels, combination subfloor underlayment to framing| |38|3/4″ and less|Deformed (2″ × 0.113″) or
Deformed (2″ × 0.120″) nail; or
8d common (21/2″ × 0.131″) nail|6|12| |39|7/8″ – 1"|8d common (21/2″ × 0.131″) nail; or
Deformed (21/2″ × 0.131″); or
Deformed (21/2″ × 0.120″) nail|6|12| |40|11/8″ − 11/4″|10d common (3″ × 0.148″) nail; or
Deformed (21/2″× 0.131″); or
Deformed (21/2″ × 0.120″) nail|6|12| |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.CRC § 0.192 High relevance — show source text
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. 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.CRC § 11.2 High relevance — show source text
R802.11.2 Rafter uplift resistance. Individual rafters shall be attached to supporting wall assemblies by connections capable of resisting uplift forces as determined by Table R802.11 or as determined by accepted engineering practice. Connections for beams used in a roof system shall be designed in accordance with accepted engineering practice.
SECTION R803—ROOF SHEATHING
R803.1 Lumber sheathing. Allowable spans for lumber used as roof sheathing shall conform to Table R803.1. Spaced lumber sheathing for wood shingle and shake roofing shall conform to the requirements of Sections R905.7 and R905.8. Spaced lumber sheathing is not allowed in Seismic Design Category D 2 .
TABLE R803.1—MINIMUM THICKNESS OF LUMBER ROOF SHEATHING Col2 ** RAFTER OR BEAM SPACING (inches)** ** MINIMUM NET THICKNESS (inches)** 24 5/8 48a 11/2 T & G 60b 60b 72c 72c For SI: 1 inch = 25.4 mm.
a. Minimum 270_F_ b, 340,000_E.
b. Minimum 420_F b, 660,000_E.
c. Minimum 600_F b, 1,150,000_E._For SI: 1 inch = 25.4 mm.
a. Minimum 270_F_ b, 340,000_E.
b. Minimum 420_F b, 660,000_E.
c. Minimum 600_F b, 1,150,000_E._R803.2 Wood structural panel sheathing.
R803.2.1 Identification and grade. Wood structural panels shall conform to DOC PS 1, DOC PS 2, CSA O325 or CSA O437, and shall be identified for grade, bond classification and performance category by a grade mark or certificate of inspection issued by an approved agency. Wood structural panels shall comply with the grades specified in Table R503.2.1.1(1).
8-30 2025 CALIFORNIA RESIDENTIAL CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
ROOF-CEILING CONSTRUCTION
R803.2.1.1 Exposure durability. Wood structural panels, when designed to be permanently exposed in outdoor applications, shall be of an exterior exposure durability. Wood structural panel roof sheathing exposed to the underside shall be permitted to be of interior type bonded with exterior glue, identified as Exposure 1.
R803.2.1.2 Fire-retardant-treated plywood. The allowable unit stresses for fire-retardant-treated plywood, including fastener values, shall be developed from an approved method of investigation that considers the effects of anticipated temperature and humidity to which the fire-retardant-treated plywood will be subjected, the type of treatment and redrying process. The fire-retardant-treated plywood shall be graded by an approved agency.
R803.2.2 Allowable spans. The maximum allowable spans for wood structural panel roof sheathing shall not exceed the values set forth in Table R503.2.1.1(1) or APA E30.
CRC § 25.4 High relevance — show source text
The cap nail shank
shall have a length sufficient to penetrate through the roof
sheathing or not less than3/4 inch into the roof sheathing.
Self-adhering polymer modified bitumen underlayment
shall be installed in accordance with the underlayment and
roof covering manufacturers’ installation instructions for the
deck material, roof ventilation configuration and climate
exposure of the roof covering.
Exception: Self-adhering polymer modified bitumen under-
layment shall not be installed under wood shakes or wood
shingles.| |Mineral-
surfaced roll
roofing|R905.5|R905.5|R905.5| |Slate and
slate-type
shingles|R905.6|R905.6|R905.6| |Wood shingles|R905.7|R905.7|R905.7| |Wood shakes|R905.8|R905.8|R905.8| |Metal panels|R905.10|R905.10|R905.10| |For SI: 1 inch = 25.4 mm, 1 mile per hour = 0.447 m/s.|For SI: 1 inch = 25.4 mm, 1 mile per hour = 0.447 m/s.|For SI: 1 inch = 25.4 mm, 1 mile per hour = 0.447 m/s.|For SI: 1 inch = 25.4 mm, 1 mile per hour = 0.447 m/s.|2025 CALIFORNIA RESIDENTIAL CODE 9-7
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
ROOF ASSEMBLIES
R905.1.2 Ice barriers. In areas where there has been a history of ice forming along the eaves causing a backup of water as designated in Table R301.2, an ice barrier shall be installed for asphalt shingles, metal roof shingles, mineral-surfaced roll roofing, slate and slate-type shingles, wood shingles and wood shakes. The ice barrier shall consist of not fewer than two layers of underlayment cemented together, or a self-adhering polymer-modified bitumen sheet shall be used in place of normal underlayment and extend from the lowest edges of all roof surfaces to a point not less than 24 inches (610 mm) inside the exterior wall line of the building.
On roofs with slope equal to or greater than 8 units vertical in 12 units horizontal (67-percent slope), the ice barrier shall be applied not less than 36 inches (914 mm) measured along the roof slope from the eave edge of the building.
Exception: Detached accessory structures not containing conditioned floor area.
R905.2 Asphalt shingles. The installation of asphalt shingles shall comply with the provisions of this section.
R905.2.1 Sheathing requirements. Asphalt shingles shall be fastened to wood structural panels or solid lumber sheathing.
R905.2.2 Slope. Asphalt shingles shall be used only on roof slopes of 2 units vertical in 12 units horizontal (17-percent slope) or greater. For roof slopes from 2 units vertical in 12 units horizontal (17-percent slope) up to 4 units vertical in 12 units horizontal (33-percent slope), double underlayment application is required in accordance with Section R905.1.1.
R905.2.3 Underlayment. Underlayment shall comply with Section R905.1.1.
Frequently asked questions
What is the difference between "exterior exposure durability" and "Exposure 1"?
Exterior exposure durability means the panel is manufactured for permanent outdoor exposure; Exposure 1 is an interior‑type panel bonded with an exterior glue allowed only when the panel is exposed to the underside, not the weather. § R803.2.1.1.
Can I use interior OSB for roof sheathing if I install a good underlayment and shingles?
No — if the sheathing is designed to be permanently exposed outdoors the code requires an exterior exposure durability panel. If the panel is only underside‑exposed (attic visible) Exposure 1 is permitted. § R803.2.1.1.
Do fire‑retardant‑treated panels require different fastener schedules?
Yes — the code requires allowable unit stresses and fastener values for FRT plywood be developed from an approved investigation that considers treatment and drying processes; FRT must be graded by an approved agency. § R803.2.1.2.
Where do I find the required nail spacing and nail type for roof sheathing?
Nail sizes, types and spacing are given in the nailing tables (e.g., Table R602.3(2)) and the roof sheathing schedules referenced in Section R803. Consult those tables for the exact spacing and ring‑shank requirements.
More in California Residential Code
Ask about the CRC
Get cited, plain-English answers on the California Residential Code for your project — any code section, any scenario.
Start Free Trial