CRC · California Residential Code
How should fascias be installed and attached to exterior walls and eaves?
The CRC requires fascias be installed per the manufacturer’s instructions; for aluminum fascia the code (§ R704.4.1.1 & § R704.4.1.2) specifies a 1‑1/4" finish nail, at **24 in o.c.** when design wind pressure is **≤ 30 psf** (inserted under the drip edge with 1" coverage) and **16 in o.c.** with both return‑leg and top‑edge nails (or snap‑lock utility trim at 6" o.c.) when pressure **exceeds 30 psf** — determine the correct wind pressure using Table R301.2.1.
Last reviewed: July 6, 2026
What the code requires — 2-4 sentences
Fascia must be installed in accordance with the manufacturer’s installation instructions; the California Residential Code point for this is § R704.4. For aluminum fascia the Code gives specific fastener sizes, required embedment under the drip edge and two different spacing regimes depending on the design wind pressure (≤ 30 psf or > 30 psf) in § R704.4.1, § R704.4.1.1, and § R704.4.1.2. The applicable design wind pressure for soffits/fascias is determined using the component and cladding loads in Table R301.2.1(1) and adjusted for height/exposure per Table R301.2.1(2) referenced in § R704.1.
The single most important rule: install fascias per the manufacturer’s instructions; for aluminum fascia follow the fastener size, spacing, and drip‑edge coverage rules tied to whether the design wind pressure is ≤ 30 psf or > 30 psf.
Requirements in detail
Short summary of the control logic
- Follow the manufacturer’s installation instructions for all fascia materials (§ R704.4).
- If the fascia is aluminum, the CRC adds prescriptive fastening and placement rules in § R704.4.1, with one set when the design wind pressure ≤ 30 psf and a stricter set when it exceeds 30 psf.
- Determine which wind-pressure bucket applies by using the component/cladding loads in Table R301.2.1(1) and adjusting for height/exposure per Table R301.2.1(2) as described in § R704.1.
Required fasteners, spacing and drip-edge requirements (aluminum fascia)
| Decision item | Required value / action | Code Reference |
|---|---|---|
| Applicable wind-pressure category | Determine from Table R301.2.1(1) (effective area 10 ft²) and Table R301.2.1(2) adjustments | § R704.1 |
| Nail size (aluminum fascia) | 1-1/4 in × 0.057 in shank × 0.177 in head dia. finish nail (32 mm × 1.4 mm × 4.5 mm) | § R704.4.1.1 / § R704.4.1.2 |
| Top-edge insertion under drip edge (≤ 30 psf) | Fascia shall be inserted under the drip edge with at least 1 in (25 mm) of fascia covered by the drip edge | § R704.4.1.1 |
| Top-edge alternative where insertion not possible (≤ 30 psf) | Top edge may be nailed ≤ 1 in below the drip edge using above nail, max spacing 24 in o.c. | § R704.4.1.1 |
| Fastener spacing (aluminum, design wind pressure ≤ 30 psf) | One finish nail in the return leg spaced ≤ 24 in o.c. | § R704.4.1.1 |
| Fastener spacing (aluminum, design wind pressure > 30 psf) | One finish nail in the return leg AND one finish nail ≤ 1 in below the drip edge — both spaced ≤ 16 in o.c. | § R704.4.1.2 |
| Alternative top-edge attachment (design wind pressure > 30 psf) | Utility trim beneath the drip edge with snap locks punched into the fascia spaced ≤ 6 in o.c. (allowed alternative to the top nail) | § R704.4.1.2 |
Notes:
- The Code’s prescriptive fastening specifics in R704.4.1.* are only for aluminum fascia; for other fascia materials the Code directs compliance with the manufacturer’s installation instructions per § R704.4.
- The Code ties wind‑category decisions back to the wind loads tables; you must compute the component/cladding loads per § R704.1 before selecting the spacing in R704.4.1.
Attachment to soffits / supporting components
- Vinyl and aluminum soffit panels (and soffit attachments) must be fastened to a supporting component such as a nailing strip, fascia, or sub‑fascia (see Figure R704.2.1(1)) and be installed per manufacturer’s instructions; fascia is called out explicitly as an attachment point in § R704.2.1.
- Where soffit materials are not addressed prescriptively, the Code again defers to the manufacturer’s instructions (see § R704.2 and § R704.3 for wind > 30 psf).
Exceptions & special cases
- The Code's prescriptive fastener sizes, spacing and drip‑edge coverage are given only for aluminum fascia; other fascia materials (wood, fiber‑cement, PVC, composite) are governed by their manufacturer's installation instructions per § R704.4 — the CRC does not provide a universal prescriptive table for those materials.
- If the fascia cannot be inserted under the drip edge, the Code specifically allows the top edge to be secured with a finish nail located not more than 1 in (25 mm) below the drip edge (see § R704.4.1.1).
- Where the design wind pressure exceeds 30 psf, an alternative to nailing the top edge is permitted: utility trim installed beneath the drip edge with snap locks punched into the fascia at ≤ 6 in o.c. (see § R704.4.1.2).
Common mistakes
- Assuming the Code’s aluminum‑fascia prescriptive spacings apply to other materials — the CRC defers to the manufacturer for non‑aluminum fascias (§ R704.4).
- Failing to determine the correct design wind pressure from Table R301.2.1(1) and Table R301.2.1(2) before selecting fastener spacing — the 30 psf breakpoint is applied to the design wind pressure, not to an arbitrary local wind speed (§ R704.1).
- Using wrong nail size or head diameter — the Code specifies the exact finish‑nail size for the aluminum prescriptive method (1‑1/4" × 0.057" × 0.177" head) in § R704.4.1.1/1.2.
- Not providing the required 1 in of fascia under the drip edge when insertion is required (≤ 30 psf) — this reduces protection and violates § R704.4.1.1.
Worked example — concrete scenario
Scenario: Single‑story house, calculated design wind pressure = 40 psf (so > 30 psf). You are installing aluminum fascia along a single continuous eave run 24 feet long.
- Which Code rules apply? Because design wind pressure exceeds 30 psf, use § R704.4.1.2 for aluminum fascia spacing and attachment.
- Required fasteners and spacing (from § R704.4.1.2):
- Nail size: 1‑1/4" × 0.057" × 0.177" finish nail.
- Spacing: one finish nail in the return leg spaced ≤ 16 in o.c., and one finish nail located ≤ 1 in below the drip edge spaced ≤ 16 in o.c. (i.e., two rows at 16" spacing).
- Count nails for the 24 ft (288 in) run:
- Nails per row = 288 in / 16 in spacing = 18 nails (round up if needed).
- Two rows required → 18 nails × 2 = 36 finish nails for the run.
- Alternative using utility trim: If you choose the permitted alternative for the top edge, install utility trim beneath the drip edge and punch snap locks into the fascia ≤ 6 in o.c. For 288 in at 6" spacing you need 288 / 6 = 48 snap locks (snap locks replace the top row of nails; you still need the return‑leg nails per § R704.4.1.2).
Related provisions
- § R704.4 — Fascia shall be installed in accordance with the manufacturer’s installation instructions.
- § R704.4.1, § R704.4.1.1, § R704.4.1.2 — Aluminum‑fascia prescriptive attachment, nail size, spacing, drip‑edge coverage and alternative snap‑lock trim.
- § R704.1 — General wind limitations; method to determine the design wind pressure that controls soffit/fascia rules.
- § R704.2 / § R704.2.1 — Soffit installation and the requirement that soffit panels be fastened to supporting components such as fascia or nailing strips (useful for how fascias act as attachment points).
- Table R301.2.1(1) and R301.2.1(2) — Component/cladding loads and height/exposure adjustments used to compute the design wind pressure referenced by § R704.1.
Code references
Grounded in the retrieved California Residential Code — click a citation to read the verbatim passage:
CRC § 7-34 High relevance — show source text
Spacing at intermediate supports shall be not greater than 12 inches on center.|
7-34 2025 CALIFORNIA RESIDENTIAL CODE
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R704.4 Fascia. Fascia shall be installed in accordance with the manufacturer’s installation instructions.
R704.4.1 Aluminum fascia. Aluminum fascia shall be installed in accordance with the manufacturer’s installation instructions and comply with Section R704.4.1.1 or R704.4.1.2.
R704.4.1.1 Fascia installation where the design wind pressure is 30 psf or less. Where the design wind pressure is 30 pounds per square foot (1.44 kPa) or less, aluminum fascia shall be a attached with one finish nail [1 [1] / 4 inches by 0.57 inch by 0.177 inch head diameter (32 mm × 14.5 mm × 4.5 mm)] in the return leg spaced a maximum of 24 inches (610 mm) on center, and the fascia shall be inserted under the drip edge with at least 1 inch (305 mm) of fascia material covered by the drip edge. Where the fascia can not be inserted under the drip edge, the top edge of the fascia shall be secured using one finish nail [1 [1] / 4 inches by 0.57 inch by 0.177 inch head diameter (32 mm × 14.5 mm × 4.5 mm)] located not more than 1 inch (25 mm) below the drip edge and spaced a maximum of 24 inches (610 mm) on center.
R704.4.1.2 Fascia installation where the design wind pressure exceeds 30 psf. Where the design wind pressure is greater than 30 pounds per square foot (1.44 kPa), aluminum fascia shall be attached with one finish nail [1 [1] / 4 inches by 0.57 inch by 0.177 inch head diameter (32 mm × 14.5 mm × 4.5 mm)] in the return leg spaced a maximum of 16 inches (406 mm) on center and one finish nail located not more than 1 inch (25 mm) below the drip edge spaced a maximum of 16 inches (406 mm) on center. As an alternative, the top edge of the fascia is permitted to be secured using utility trim installed beneath the drip edge with snap locks punched into the fascia spaced not more than 6 inches (152 mm) on center.
SECTION R705—BIPV SYSTEMS FOR EXTERIOR WALL COVERINGS AND FENESTRATION
R705.1 Listing required. In addition to complying with other provisions of this code, building-integrated photovoltaic (BIPV) systems used as exterior wall coverings or fenestration shall be listed and labeled in accordance with UL 1703 or both UL 61730-1 and UL 61730-2.
2025 CALIFORNIA RESIDENTIAL CODE 7-35
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7-36 2025 CALIFORNIA RESIDENTIAL CODE
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CALIFORNIA RESIDENTIAL CODE – MATRIX ADOPTION TABLE
CHAPTER 8 – ROOF-CEILING CONSTRUCTION
CRC § 0.42 High relevance — show source text
Fastener spacing applies where wood exterior soffit framing member-specific gravity is 0.42 or larger. Where the specific gravity of exterior soffit framing members is greater
than or equal to 0.35 but less than 0.42 in accordance with AWC NDS, the fastener spacing shall be multiplied by 0.67 or the same fastener spacing as prescribed for galvanized
steel nails shall be permitted to be used where RSRS-01 (2-inch by 0.099-inch by 0.266-inch head) nails replace 6d box nails and RSRS-03 (21/2-inch × 0.131-inch × 0.281-inch
head) nails replace 8d common nails or 10d box nails. RSRS is a Roof Sheathing Ring Shank nail meeting the specifications in ASTM F1667. Framing members shall be mini-
mum 2 × 3 nominal with the larger dimension in the cross section aligning with the length of fasteners to provide sufficient embedment depths.
f. Spacing at intermediate supports shall be not greater than 12 inches on center.|7-34 2025 CALIFORNIA RESIDENTIAL CODE
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R704.4 Fascia. Fascia shall be installed in accordance with the manufacturer’s installation instructions.
R704.4.1 Aluminum fascia. Aluminum fascia shall be installed in accordance with the manufacturer’s installation instructions and comply with Section R704.4.1.1 or R704.4.1.2.
R704.4.1.1 Fascia installation where the design wind pressure is 30 psf or less. Where the design wind pressure is 30 pounds per square foot (1.44 kPa) or less, aluminum fascia shall be a attached with one finish nail [1 [1] / 4 inches by 0.57 inch by 0.177 inch head diameter (32 mm × 14.5 mm × 4.5 mm)] in the return leg spaced a maximum of 24 inches (610 mm) on center, and the fascia shall be inserted under the drip edge with at least 1 inch (305 mm) of fascia material covered by the drip edge. Where the fascia can not be inserted under the drip edge, the top edge of the fascia shall be secured using one finish nail [1 [1] / 4 inches by 0.57 inch by 0.177 inch head diameter (32 mm × 14.5 mm × 4.5 mm)] located not more than 1 inch (25 mm) below the drip edge and spaced a maximum of 24 inches (610 mm) on center.
CRC § 0.0134 High relevance — show source text
Mechanically fastened underlayment shall be
fastened using annular ring or deformed shank nails
with 1-inch diameter metal or plastic caps. Metal caps
shall have a thickness of not less than 32-gage (0.0134
inch) sheet metal. Power-driven metal caps shall have a
minimum thickness of 0.010 inch. Minimum thickness of
the outside edge of plastic caps shall be 0.035 inch. The
cap nail shank shall be not less than 0.083 inch. 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 instruc-
tions for the deck material, roof ventilation
configuration and climate exposure of the roof
covering.| |Clay and concrete tile|1507.3|1507.3|1507.3| |BIPV roof coverings|1507.16|1507.16|1507.16| |Metal roof panels|1507.4|Manufacturer’s installation instructions|Mechanically fastened underlayment shall be fastened
with corrosion-resistant fasteners in a grid pattern of not
greater than 12 inches horizontally and vertically between
side laps with a 6-inch spacing at side and end laps.
Mechanically fastened underlayment shall be fastened
using annular ring or deformed shank nails with 1-inch
diameter metal or plastic caps. Metal caps shall have a
thickness of not less than 32-gage sheet metal. Power-
driven metal caps shall have a minimum thickness of
0.010 inch. Minimum thickness of the outside edge of
plastic caps shall be 0.035 inch. The cap nail shank shall
be not less than 0.083 inch. 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 instruc-
tions for the deck material, roof ventilation configuration
and climate exposure of the roof covering.| |Metal roof shingles|1507.5|1507.5|1507.5| |Mineral-surfaced roll
roofing|1507.6|1507.6|1507.6| |Slate shingles|1507.7|1507.7|1507.7| |Wood shingles|1507.8|1507.8|1507.8| |Wood shakes|1507.9|1507.9|1507.9| |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.|CRC § 7-33 High relevance — show source text
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R704.3 Exterior soffit installation where the design wind pressure exceeds 30 psf. Where the design wind pressure is greater than 30 psf, exterior soffit installation shall comply with Section R704.3.1, R704.3.2, R704.3.3 or R704.3.4. Exterior soffit materials not addressed in Sections R704.3.1 through R704.3.4 shall be in accordance with the manufacturer’s installation instructions.
R704.3.1 Vinyl exterior soffit panels. Vinyl exterior soffit panels and their attachments shall be capable of resisting wind loads specified in Table R301.2.1(1) for walls using an effective wind area of 10 square feet (0.929 m [2] ) and adjusted for height and exposure in accordance with Table R301.2.1(2). Vinyl exterior soffit panels shall be installed using fasteners specified by the manufacturer and shall be fastened at both ends to a supporting component such as a nailing strip, fascia or subfascia component in accordance with Figure R704.2.1(1). Where the unsupported span of exterior soffit panels is greater than 12 inches (305 mm), intermediate nailing strips shall be provided in accordance with Figure R704.2.1(2). Vinyl exterior soffit panels shall be installed in accordance with the manufacturer’s installation instructions.
R704.3.2 Fiber-cement exterior soffit panels. F iber-cement exterior soffit panels shall comply with Section R704.2.2 and shall be capable of resisting wind loads specified in Table R301.2.1(1) for walls using an effective wind area of 10 square feet (0.929 m [2] ) and adjusted for height and exposure in accordance with Table R301.2.1(2).
R704.3.3 Hardboard exterior soffit panels. Hardboard exterior soffit panels shall comply with the manufacturer’s installation instructions and shall be capable of resisting wind loads specified in Table R301.2.1(1) for walls using an effective wind area of 10 square feet (0.929 m [2] ) and adjusted for height and exposure in accordance with Table R301.2.1(2).
R704.3.4 Wood structural panel exterior soffit. Wood structural panel exterior soffits shall be capable of resisting wind loads specified in Table R301.2.1(1) for walls using an effective wind area of 10 square feet (0.929 m [2] ) and adjusted for height and exposure in accordance with Table R301.2.1(2). Alternatively, wood structural panel exterior soffits shall be installed in accordance with Table R704.3.4.
|TABLE R704.3.4—PRESCRIPTIVE ALTERNATIVE FOR WOOD STRUCTURAL PANEL EXTERIOR SOFFIT b, c, d,
CRC § 1412.7 High relevance — show source text
1412.7 Aluminum fascia. Aluminum fascia shall comply with Section 1412.2 and shall be not less than 0.019 inches (0.48 mm) in thickness and installed in accordance with manufacturer’s instructions. Aluminum fascia shall be attached to wood frame construc tion in accordance with Section 1412.7.1 or 1412.7.2.
1412.7.1 Fascia installation where the design wind pressure is 30 psf (1.44 kN/m [2] ) or less. Where the design wind pressure is 30 pounds per square foot (1.44 kN/m [2] ) or less, aluminum fascia shall be a attached with one finish nail (1 [1] / 4 inches × 0.057 inch × 0.177 inch head diameter) (32 mm × 1.4 mm × 4.5 mm) in the return leg spaced not greater than 24 inches (610 mm) on center, and the fascia shall be inserted under the drip edge with not less than 1 inch (25 mm) of fascia material covered by the drip edge. Where the fascia cannot be inserted under the drip edge, the top edge of the fascia shall be secured using one finish nail (1 [1] / 4 inches × 0.057 inch × 0.177 inch head diameter) (32 mm × 1.4 mm × 4.5 mm) located not more than 1 inch (25 mm) below the drip edge and spaced not greater than 24 inches (610 mm) on center. 1412.7.2 Fascia installation where the design wind pressure exceeds 30 psf (1.44 kN/m [2] ). Where the design wind pressure is greater than 30 pounds per square foot (1.44 kN/m [2] ), aluminum fascia shall be attached with one finish nail (1 [1] / 4 inches × 0.057 inch × 0.177 inch head diameter) (32 mm × 1.4 mm × 4.5 mm) in the return leg spaced a maximum of 16 inches (406 mm) on center and one finish nail located not greater than 1 inch (25 mm) below the drip edge spaced a maximum of 16 inches (406 mm) on center. As an alternative, the top edge of the fascia is permitted to be secured using utility trim installed beneath the drip edge with snap locks punched into the fascia spaced not greater than 6 inches (152 mm) on center.
SECTION 1413—[DSA-SS & DSA-SS/CC, OSHPD 1, 1R, 2, 4 & 5] ADDITIONAL REQUIREMENTS FOR ANCHORED AND ADHERED VENEER
1413.1 General. In no case shall veneer be considered as part of the backing in computing strength or deflection, nor shall it be consid- ered a part of the required thickness of the backing.
Veneer shall be anchored in a manner which will not allow relative movement between the veneer and the wall.
Anchored or adhered veneer shall not be used on overhead horizontal surfaces.
CRC § 1412.7.2 High relevance — show source text
1412.7.2 Fascia installation where the design wind pressure exceeds 30 psf (1.44 kN/m [2] ). Where the design wind pressure is greater than 30 pounds per square foot (1.44 kN/m [2] ), aluminum fascia shall be attached with one finish nail (1 [1] / 4 inches × 0.057 inch × 0.177 inch head diameter) (32 mm × 1.4 mm × 4.5 mm) in the return leg spaced a maximum of 16 inches (406 mm) on center and one finish nail located not greater than 1 inch (25 mm) below the drip edge spaced a maximum of 16 inches (406 mm) on center. As an alternative, the top edge of the fascia is permitted to be secured using utility trim installed beneath the drip edge with snap locks punched into the fascia spaced not greater than 6 inches (152 mm) on center.
SECTION 1413—[DSA-SS & DSA-SS/CC, OSHPD 1, 1R, 2, 4 & 5] ADDITIONAL REQUIREMENTS FOR ANCHORED AND ADHERED VENEER
1413.1 General. In no case shall veneer be considered as part of the backing in computing strength or deflection, nor shall it be consid- ered a part of the required thickness of the backing.
Veneer shall be anchored in a manner which will not allow relative movement between the veneer and the wall.
Anchored or adhered veneer shall not be used on overhead horizontal surfaces.
1413.2 Adhered veneer. Units of tile, masonry, stone or terra cotta which exceed [5] / 8 inch (15.9 mm) in thickness shall be applied as for anchored veneer where used over exit ways or more than 20 feet (6.1 m) in height above adjacent ground elevation.
1413.2.1 Bond strength and tests. Irrespective of the mortar type, veneer type or design methodology used, adhered masonry veneer shall develop a bond shear strength to the backing of at least 50 psi (345 kPa) based on gross unit bonded area. The bond between adhered veneer units and backing shall be shear tested, in accordance with ASTM C1823, on a field-constructed mock-up using the specified unit, mortar and substrate.
Not less than two shear tests shall be performed for the adhered veneer between the units and the supporting element. At least one shear test shall be performed at each building for each 5,000 square feet (465 m [2] ) of wall area or fraction thereof.
1413.2.2 TMS 402, Section 13.3.2.2. Replace TMS 402, Section 13.3.2.2 (c) with the following: (c) The weight of adhered masonry veneer units shall not exceed 15 psf (73 kg/m [2] ).
2025 CALIFORNIA BUILDING CODE 14-23
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CALIFORNIA BUILDING CODE – MATRIX ADOPTION TABLE
CRC § 25.4 High relevance — show source text
Spacing at intermediate supports is permitted to be 12 inches on center.|For SI: 1 inch = 25.4 mm.
a. Fasteners shall comply with Section 1412.6.
b. Maximum spacing of soffit framing members shall not exceed 24 inches (610 mm).
c. Wood structural panels shall be of an exterior exposure grade.
d. Wood structural panels shall be installed with strength axis perpendicular to supports with a minimum of two continuous spans.
e. Wood structural panels shall be attached to soffit framing members with specific gravity of at least 0.42. Framing members shall be minimum 2″ x 3″ nominal with the larger
dimension in the cross section aligning with the length of fasteners to provide sufficient embedment depths.
f. Spacing at intermediate supports is permitted to be 12 inches on center.|For SI: 1 inch = 25.4 mm.
a. Fasteners shall comply with Section 1412.6.
b. Maximum spacing of soffit framing members shall not exceed 24 inches (610 mm).
c. Wood structural panels shall be of an exterior exposure grade.
d. Wood structural panels shall be installed with strength axis perpendicular to supports with a minimum of two continuous spans.
e. Wood structural panels shall be attached to soffit framing members with specific gravity of at least 0.42. Framing members shall be minimum 2″ x 3″ nominal with the larger
dimension in the cross section aligning with the length of fasteners to provide sufficient embedment depths.
f. Spacing at intermediate supports is permitted to be 12 inches on center.|1412.7 Aluminum fascia. Aluminum fascia shall comply with Section 1412.2 and shall be not less than 0.019 inches (0.48 mm) in thickness and installed in accordance with manufacturer’s instructions. Aluminum fascia shall be attached to wood frame construc tion in accordance with Section 1412.7.1 or 1412.7.2.
1412.7.1 Fascia installation where the design wind pressure is 30 psf (1.44 kN/m [2] ) or less. Where the design wind pressure is 30 pounds per square foot (1.44 kN/m [2] ) or less, aluminum fascia shall be a attached with one finish nail (1 [1] / 4 inches × 0.057 inch × 0.177 inch head diameter) (32 mm × 1.4 mm × 4.5 mm) in the return leg spaced not greater than 24 inches (610 mm) on center, and the fascia shall be inserted under the drip edge with not less than 1 inch (25 mm) of fascia material covered by the drip edge. Where the fascia cannot be inserted under the drip edge, the top edge of the fascia shall be secured using one finish nail (1 [1] / 4 inches × 0.057 inch × 0.177 inch head diameter) (32 mm × 1.4 mm × 4.5 mm) located not more than 1 inch (25 mm) below the drip edge and spaced not greater than 24 inches (610 mm) on center. 1412.7.2 Fascia installation where the design wind pressure exceeds 30 psf (1.44 kN/m [2] **).
CRC § 1.44 High relevance — show source text
R704.2 Exterior Soffit installation where the design wind pressure is 30 psf or less. Where the design wind pressure is 30 pounds per square foot (1.44 kPa) or less, exterior soffit installation shall comply with Section R704.2.1, R704.2.2, R704.2.3 or R704.2.4. Soffit materials not addressed in Sections R704.2.1 through R704.2.4 shall be in accordance with the manufacturer’s installation instructions.
R704.2.1 Vinyl and aluminum exterior soffit panels. Vinyl and aluminum exterior soffit panels shall be installed using aluminum, galvanized, stainless steel or rust-preventative coated nails or staples or other approved corrosion-resistant fasteners specified by the manufacturer and shall be fastened at both ends to a supporting component such as a nailing strip, fascia or subfascia component in accordance with Figure R704.2.1(1). Where the unsupported span of exterior soffit panels is greater than 16 inches (406 mm), intermediate nailing strips shall be provided in accordance with Figure R704.2.1(2). Vinyl and aluminum exterior soffit panels shall be installed in accordance with the manufacturer’s installation instructions. Fascia covers shall be installed in accordance with the manufacturer’s installation instructions.
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FIGURE R704.2.1(1)—TYPICAL SINGLE-SPAN VINYL AND ALUMINUM EXTERIOR SOFFIT PANEL SUPPORT
FASCIA SHALL BE
INSTALLED IN ACCORDANCE
WITH SECTION R704.4.
ATTACH EXTERIOR
SOFFIT
TO SUB-FASCIA OR
TO NAILING STRIP (NOT SHOWN)
RDANCE
.4.
FRAMING
MIN. 1X2 NAILING
STRIPCol2 Col3 Col4 Col5 Col6 Col7 R
OR
VINYL AND ALUMINUM
EXTERIOR SOFFIT
J-CHANNEL
UNSUPPORTED SPAN
LIMITED PER SECTION R704.2.1 OR R704.3.1R
OR
VINYL AND ALUMINUM
EXTERIOR SOFFIT
J-CHANNEL
UNSUPPORTED SPAN
LIMITED PER SECTION R704.2.1 OR R704.3.1R
OR
VINYL AND ALUMINUM
EXTERIOR SOFFIT
J-CHANNEL
UNSUPPORTED SPAN
LIMITED PER SECTION R704.2.1 OR R704.3.1R
OR
VINYL AND ALUMINUM
EXTERIOR SOFFIT
J-CHANNEL
UNSUPPORTED SPAN
LIMITED PER SECTION R704.2.1 OR R704.3.1R
OR
VINYL AND ALUMINUM
EXTERIOR SOFFIT
J-CHANNEL
UNSUPPORTED SPAN
LIMITED PER SECTION R704.2.1 OR R704.3.1R
OR
VINYL AND ALUMINUM
EXTERIOR SOFFIT
J-CHANNEL
UNSUPPORTED SPAN
LIMITED PER SECTION R704.2.CRC § 2.1 High relevance — show source text
2.1 OR R704.3.1|R
OR
VINYL AND ALUMINUM
EXTERIOR SOFFIT
J-CHANNEL
UNSUPPORTED SPAN
LIMITED PER SECTION R704.2.1 OR R704.3.1|R
OR
VINYL AND ALUMINUM
EXTERIOR SOFFIT
J-CHANNEL
UNSUPPORTED SPAN
LIMITED PER SECTION R704.2.1 OR R704.3.1|FIGURE R704.2.1(2)—TYPICAL DOUBLE-SPAN VINYL AND ALUMINUM EXTERIOR SOFFIT PANEL SUPPORT
R704.2.2 Fiber-cement exterior soffit panels. Fiber-cement exterior soffit panels shall be a minimum of [1] / 4 inch (6.4 mm) in thickness and shall comply with the requirements of ASTM C1186, Type A, minimum Grade II, or ISO 8336, Category A, minimum Class 2. Panel joints shall occur over framing or over wood structural panel sheathing. Exterior soffit panels shall be installed with spans and fasteners in accordance with the manufacturer’s installation instructions. R704.2.3 Hardboard exterior soffit panels. Hardboard exterior soffit panels shall be not less than [7] / 16 inch (11.11 mm) in thickness and shall be fastened to framing or nailing strips with 2 [1] / 2 -inch by 0.113-inch (64 mm by 2.9 mm) siding nails spaced not more than 6 inches (152 mm) on center at panel edges and 12 inches (305 mm) on center at intermediate supports.
R704.2.4 Wood structural panel exterior soffit. The minimum nominal thickness for wood structural panel exterior soffits shall be [3] / 8 inch (9.5 mm) and shall be fastened to framing or nailing strips with 2-inch by 0.099-inch (51 mm by 2.5 mm) nails. Fasteners shall be spaced not less than 6 inches (152 mm) on center at panel edges and 12 inches (305 mm) on center at intermediate supports.
2025 CALIFORNIA RESIDENTIAL CODE 7-33
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
WALL COVERING
R704.3 Exterior soffit installation where the design wind pressure exceeds 30 psf. Where the design wind pressure is greater than 30 psf, exterior soffit installation shall comply with Section R704.3.1, R704.3.2, R704.3.3 or R704.3.4. Exterior soffit materials not addressed in Sections R704.3.1 through R704.3.4 shall be in accordance with the manufacturer’s installation instructions.
R704.3.1 Vinyl exterior soffit panels. Vinyl exterior soffit panels and their attachments shall be capable of resisting wind loads specified in Table R301.2.1(1) for walls using an effective wind area of 10 square feet (0.929 m [2] ) and adjusted for height and exposure in accordance with Table R301.2.1(2). Vinyl exterior soffit panels shall be installed using fasteners specified by the manufacturer and shall be fastened at both ends to a supporting component such as a nailing strip, fascia or subfascia component in accordance with Figure R704.2.1(1).
CRC § 1507.1.1 High relevance — show source text
End laps shall be 4
inches and shall be offset by 6 feet.
3.
A single layer of self-adhering polymer modified
bitumen underlayment complying with ASTM
D1970, 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.|Underlayment shall be one of the following:
1.
Two layers of mechanically fastened underlayment
applied in the following manner: Apply a strip of
underlayment that is half the width of a full sheet
parallel to and starting at the eaves, fastened
sufficiently to hold in place. Starting at the eaves,
apply full-width sheets of underlayment,
overlapping successive sheets half the width of a full
sheet plus 2 inches. Distortions in the underlayment
shall not interfere with the ability of the shingles to
seal. End laps shall be 4 inches and shall be offset by
6 feet.
2.
A strip not less than 4 inches in width of self-
adhering polymer modified bitumen underlayment
complying with ASTM D1970, installed in
accordance with the manufacturer’s installation
instructions for the deck material, shall be applied
over all joints in the roof decking. An approved
underlayment complying with Table 1507.1.1(1) for
the applicable roof covering and basic wind speed
shall be applied over the entire roof over the 4-inch-
wide membrane strips. Underlayment shall be
applied in accordance with this table using the
application requirements for where the maximum
basic wind speed is less than 130 mph.
3.
A single layer of self-adhering polymer modified
bitumen underlayment complying with ASTM
D1970, installed in accordance with the
underlayment and roof covering manufacurers’
installation instructions for the deck material, roof
ventilation configuration, and climate exposure of
the roof covering.|15-8 2025 CALIFORNIA BUILDING CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
ROOF ASSEMBLIES AND ROOFTOP STRUCTURES
TABLE 1507.1.1(2)—UNDERLAYMENT APPLICATION—continued Col2 Col3 Col4 ROOF
COVERINGSECTION MAXIMUM BASIC WIND SPEED,****V < 130 MPH IN
HURRICANE-PRONE REGIONS ORV < 140 MPH
OUTSIDE HURRICANE-PRONE REGIONSMAXIMUM BASIC WIND SPEED,****V ≥ 130 MPH IN
HURRICANE-PRONE REGIONS ORV ≥ 140 MPH
OUTSIDE HURRICANE-PRONE REGIONSMetal roof
panels1507.4 Apply in accordance with the manufacturer’s installa-
tion instructionsUnderlayment shall be one of the following:
1.CRC § 1.44 High relevance — show source text
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
WALL COVERING
R703.17 Cladding attachment over foam sheathing to masonry or concrete wall construction. Cladding shall be specified and installed in accordance with Section R703.3 and the cladding manufacturer’s instructions or an approved design. Foam sheathing shall be attached to masonry or concrete construction in accordance with the insulation manufacturer’s installation instructions or an approved design. Furring and furring attachments through foam sheathing into concrete or masonry substrate shall be designed to resist design loads determined in accordance with Section R301, including support of cladding weight as applicable. Fasteners used to attach cladding or furring through foam sheathing to masonry or concrete substrates shall be approved for application into masonry or concrete material and shall be installed in accordance with the fastener manufacturer’s instructions.
Exceptions:
- Where the cladding manufacturer has provided approved installation instructions for application over foam sheathing and connection to a masonry or concrete substrate, those requirements shall apply.
- For exterior insulation and finish systems, refer to Section R703.9.
- For anchored masonry or stone veneer installed over foam sheathing, refer to Section R703.8.
R703.18 Fiber-mat reinforced cementitious backer units. Fiber-mat reinforced cementitious backer units used on exterior walls as a substrate for the application of exterior finish materials shall comply with ASTM C1325. Installation shall be in accordance with the manufacturer’s installation instructions. Backer units shall be installed using corrosion-resistant fasteners. Finish materials shall be installed in accordance with the manufacturer’s instructions.
SECTION R704 —EXTERIOR SOFFITS AND FASCIAS
R704.1 General wind limitations. Where the design wind pressure is 30 pounds per square foot (1.44 kPa) or less, exterior soffits shall comply with Section R704.2. Where the design wind pressure exceeds 30 pounds per square foot (1.44 kPa), exterior soffits shall comply with Section R704.3. The design wind pressure on exterior soffits shall be determined using the component and cladding loads specified in Table R301.2.1(1) for walls using an effective wind area of 10 square feet (0.93 m [2] ) and adjusted for height and exposure in accordance with Table R301.2.1(2).
R704.2 Exterior Soffit installation where the design wind pressure is 30 psf or less. Where the design wind pressure is 30 pounds per square foot (1.44 kPa) or less, exterior soffit installation shall comply with Section R704.2.1, R704.2.2, R704.2.3 or R704.2.4. Soffit materials not addressed in Sections R704.2.1 through R704.2.4 shall be in accordance with the manufacturer’s installation instructions.
R704.2.1 Vinyl and aluminum exterior soffit panels. Vinyl and aluminum exterior soffit panels shall be installed using aluminum, galvanized, stainless steel or rust-preventative coated nails or staples or other approved corrosion-resistant fasteners specified by the manufacturer and shall be fastened at both ends to a supporting component such as a nailing strip, fascia or subfascia component in accordance with Figure R704.2.1(1). Where the unsupported span of exterior soffit panels is greater than 16 inches (406 mm), intermediate nailing strips shall be provided in accordance with Figure R704.2.1(2).
Frequently asked questions
Can I use a different nail than the one the Code lists for aluminum fascia?
The Code prescribes the finish‑nail size for the aluminum prescriptive method in § R704.4.1.1 / § R704.4.1.2; using a different fastener is not covered by that prescription — either follow the manufacturer’s instructions (per § R704.4) or use an approved alternative design.
What if my project is in a high‑wind area — does the spacing change?
Yes. The Code distinguishes ≤ 30 psf versus > 30 psf design wind pressure. Where the design wind pressure exceeds 30 psf, the required fastener spacing becomes 16 in o.c. and a second top nail (or utility trim with snap locks at ≤ 6 in o.c.) is required per § R704.4.1.2.
The fascia can't be slipped under the drip edge — what then?
If fascia cannot be inserted under the drip edge, the Code allows the top edge to be secured with one finish nail located not more than 1 in below the drip edge, with spacing defined by the wind‑pressure bucket (see § R704.4.1.1 and § R704.4.1.2).
Does the Code tell me how to fasten wood or composite fascia?
No prescriptive fastening table for non‑aluminum fascia is provided in R704. The Code requires those fascias be installed per the manufacturer’s installation instructions (see § R704.4).
Where do I find the design wind pressure to choose the right rule?
Calculate the design wind pressure using the component/cladding loads in Table R301.2.1(1) (use an effective area of 10 ft²) and adjust for height/exposure per Table R301.2.1(2); § R704.1 directs you to that method.
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