CBC · California Building Code

Fasteners, connectors and corrosion requirements for treated and exterior wood

If wood is preservative‑treated or fire‑retardant‑treated and the fasteners or connectors touch it, the CBC requires corrosion‑resistant materials (hot‑dipped galvanized to ASTM A153, stainless steel, silicon bronze or copper); staples must be stainless and connector coatings should follow manufacturer guidance or ASTM A653 Type G185 when none is provided (see §§ 2304.10.6, 2304.10.6.3 and 2304.10.6.4).

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Last reviewed: July 5, 2026

What the code requires — 2-4 sentences

The CBC requires corrosion-resistant fasteners and connectors when they are in contact with preservative‑treated or fire‑retardant‑treated wood; the materials and minimum coating classes are specified or tied to manufacturer recommendations in Chapter 23. See § 2304.10.6 for the overall requirement and § 2304.10.6.3–.4 for the specific rules that apply to fire‑retardant‑treated wood used outdoors, in wet/damp locations, and indoors. The code also ties zinc coating weights and driven‑fastener material standards to referenced ASTM specifications. § 2304.10.6 § 2304.10.6.3 § 2304.10.6.4

Requirements in detail

Basic rule and referenced standards

The general requirement for fasteners and connectors in contact with preservative‑treated and fire‑retardant‑treated wood is set out in § 2304.10.6; the section also requires zinc‑coating weights to follow ASTM A153 and references ASTM A641 and ASTM F1667 for specific fastener material standards. § 2304.10.6
For preservative‑treated wood, the code requires hot‑dipped zinc‑coated (galvanized) steel, stainless steel, silicon bronze or copper for fasteners (nuts and washers included); staples must be stainless steel. Connectors used in exterior contact with treated wood must follow the treated‑wood or connector manufacturer’s coating recommendations; if the manufacturer gives no guidance, a minimum of ASTM A653 Type G185 zinc coating (or equivalent) is required. § 2304.10.6.1
For fire‑retardant‑treated wood used in exterior or wet/damp locations, the permitted fastener materials are the same as for preservative‑treated wood (hot‑dipped zinc‑coated galvanized steel, stainless steel, silicon bronze or copper); staples must be stainless steel. § 2304.10.6.3
For fire‑retardant‑treated wood used in interior locations, fasteners must follow the manufacturer’s recommendations; if none are provided, the exterior/wet‑location rules of § 2304.10.6.3 apply. § 2304.10.6.4
The code allows mechanically‑deposited zinc coatings (electrogalvanizing) for fasteners other than nails, staples, timber rivets, wood screws and lag screws if they meet ASTM B695 Class 55 minimum. Zinc‑coated nails specifically must meet ASTM A153 coating weights (nails: ASTM A153 Class D or ASTM A641 Class 3S is cited for minimum). Stainless driven fasteners must meet ASTM F1667. § 2304.10.6 and § 2304.10.6.1

Decision table (quick reference)

Condition / Use	Accepted fastener materials / coating minimums	Notes / scope	Code Reference
Preservative‑treated wood (general)	Hot‑dipped zinc‑coated galvanize, stainless steel, silicon bronze or copper; staples = stainless	For connectors in exterior contact, follow manufacturer; absent guidance, use ASTM A653 Type G185 (or equivalent)	§ 2304.10.6.1
Fire‑retardant‑treated wood — exterior or wet/damp	Hot‑dipped zinc‑coated galvanize, stainless steel, silicon bronze or copper; staples = stainless	Applies where FR‑treated wood is used outdoors or in wet/damp locations	§ 2304.10.6.3
Fire‑retardant‑treated wood — interior	Per manufacturer; if none, follow § 2304.10.6.3 (exterior/wet)	Code defers to manufacturer first	§ 2304.10.6.4
Mechanically deposited zinc (electrogalvanized)	Permitted for fasteners other than nails, staples, timber rivets, wood screws, lag screws if ASTM B695 Class 55 min	Not permitted for the excluded fastener types unless specifically allowed elsewhere	§ 2304.10.6.1
Zinc coating weights and driven fastener standards	Hot‑dipped coatings per ASTM A153; zinc‑coated nails ASTM A153 Class D or ASTM A641 Class 3S (≈1 oz/ft2 listed); stainless driven fasteners per ASTM F1667	Code references these ASTM standards for coating weight and material	§ 2304.10.6
Exception (interior, dry)	Plain carbon steel fasteners permitted in SBX/DOT and zinc borate preservative‑treated wood	Limited exception only where those preservative types are used in interior dry environments	§ 2304.10.6.1 (Exception)

What the code does not specify (in these sections)

The CBC sections retrieved do not specify particular stainless steel grades (for example, 304 vs 316), nor do they provide a full list of compatible fastener coatings for every preservative chemistry — the code defers such detailed compatibility to manufacturer recommendations or referenced ASTM/connector standards. § 2304.10.6.1 § 2304.10.6.4

Exceptions & special cases

The code explicitly allows plain carbon steel fasteners (including nuts and washers) in SBX/DOT and zinc borate preservative‑treated wood when used in an interior, dry environment (this is a narrow, stated exception). § 2304.10.6.1 (Exception)
Connectors (e.g., hangers, plates) used in exterior applications and in contact with preservative‑treated wood must follow the treated‑wood or connector manufacturer’s coating recommendations. If the connector manufacturer gives no recommendation, the connector must be at least ASTM A653 Type G185 zinc‑coated galvanized steel (or equivalent). This shifts some selection responsibility to manufacturers. § 2304.10.6.1
For fire‑retardant‑treated wood installed indoors, if the FR‑wood manufacturer provides fastener guidance, that guidance controls. If the manufacturer does not, then the code requires the same materials as for exterior/wet locations (§ 2304.10.6.3). § 2304.10.6.4

Common mistakes

Assuming “galvanized” always means acceptable: the code requires specific coating standards (ASTM A153 for hot‑dipped, ASTM B695 Class 55 for some electrogalvanized items). Specifying a generic “galvanized” fastener without confirming the coating type/class can be non‑compliant. § 2304.10.6
Using mechanically deposited zinc (electrogalvanized) for nails or staples where the code excludes them — electrogalvanized is allowed only for certain fasteners (not nails, staples, timber rivets, wood screws, lag screws) unless other code text allows. § 2304.10.6.1
Failing to follow connector manufacturer recommendations (or to use the ASTM A653 G185 default when no recommendation exists) for connectors in exterior contact with treated wood. § 2304.10.6.1
Treating fire‑retardant‑treated wood as if it had the same interior requirements as untreated wood; for interior FR wood the manufacturer’s guidance is controlling — if none is provided, the more corrosion‑resistant materials required for exterior/wet use apply. § 2304.10.6.4

Worked example — choosing fasteners for an exterior deck built with preservative‑treated joists and decking

Scenario: Exterior deck framing and decking are pressure‑preservative treated and exposed to the weather. You need to specify fasteners and connectors for joist hangers, decking screws and ledger attachments.

How to apply the CBC rules:

Fastener material: Because the wood is preservative‑treated and exterior, specify hot‑dipped zinc‑coated galvanized steel, stainless steel, silicon bronze or copper for fasteners and connectors (nuts and washers included). Staples must be stainless steel. This follows § 2304.10.6.1.
Coating standard for nails/screws: For zinc‑coated fasteners (hot‑dipped), ensure coating weights meet ASTM A153. For zinc‑coated nails the code specifically references ASTM A153 Class D or ASTM A641 Class 3S (noting the Class D/Class 3S equivalence to roughly 1 oz/ft2 as the referenced standard indicates). § 2304.10.6 and § 2304.10.6.1
Connectors (joist hangers): Follow the hanger manufacturer’s coating recommendation for exterior use. If the hanger manufacturer gives no coating guidance, specify connectors with at least ASTM A653 Type G185 zinc coating (or equivalent) per § 2304.10.6.1.
Practical selection (example numbers grounded in the code): for ledger/joist hanger connections choose hot‑dipped galvanized hangers with ASTM A653 G185 coating; use hot‑dipped galvanized or stainless lag screws that meet ASTM A153 coating for the lag screw plating. For deck screws used in decking, use stainless steel or hot‑dipped zinc‑coated screws that meet the referenced ASTM standards (and confirm the screw manufacturer certifies coating to ASTM A153 or that the screw is specified as stainless to ASTM F1667). § 2304.10.6 § 2304.10.6.1

Caveat: the sections provided do not tell you which stainless grade to choose (304 vs 316) or specify exact screw lengths/diameters — those details are selected by structural requirements and by manufacturer guidance, and compatibility with the preservative chemistry. § 2304.10.6.4

Related provisions (other CBC / CRC sections you should check)

§ 2304.10.6.1 — Fasteners and connectors for preservative‑treated wood (details & exception)
§ 2304.10.6.2 — Fastenings for wood foundations (see AWC PWF reference)
§ 2304.10.6.3 — Fasteners for fire‑retardant‑treated wood used in exterior or wet locations (controlling for FR wood outdoors)
§ 2304.10.6.4 — Fasteners for fire‑retardant‑treated wood used in interior locations (manufacturer guidance controls)
CBC § 1507.9.7 — Wood shake attachment requires corrosion‑resistant fasteners and minimum penetration (relevant for roofing with treated or exterior wood)
CRC R304.3 and R304.3.1–.4 — Residential code parallels for treated and FR wood fasteners and connectors (useful for one- and two‑family dwellings)

Code references

Grounded in the retrieved California Building Code — click a citation to read the verbatim passage:

CBC § 23-21 High relevance — show source text
2025 CALIFORNIA BUILDING CODE 23-21

on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

WOOD

with ASTM A153. The coating weight for zinc-coated nails shall be in accordance with ASTM A153 Class D or ASTM A641 Class 3S [1 ounce per square foot (305 g/m [2] )]. Stainless steel driven fasteners shall be in accordance with the material requirements of ASTM F1667.

2304.10.6.1 Fasteners and connectors for preservative-treated wood. Fasteners, including nuts and washers, in contact with preservative-treated wood shall be of hot-dipped zinc-coated galvanized steel, stainless steel, silicon bronze or copper. Staples shall be of stainless steel. Fasteners other than nails, staples, timber rivets, wood screws and lag screws shall be permitted to be of mechanically deposited zinc-coated steel with coating weights in accordance with ASTM B695, Class 55 minimum. Connectors that are used in exterior applications and in contact with preservative-treated wood shall have coating types and weights in accordance with the treated wood or connector manufacturer’s recommendations. In the absence of manufacturer’s recommendations, not less than ASTM A653, Type G185 zinc-coated galvanized steel, or equivalent, shall be used.

Exception: Plain carbon steel fasteners, including nuts and washers, in SBX/DOT and zinc borate preservative-treated wood in an interior, dry environment shall be permitted.

2304.10.6.2 Fastenings for wood foundations. Fastenings, including nuts and washers, for wood foundations shall be as required in AWC PWF.

2304.10.6.3 Fasteners for fire-retardant-treated wood used in exterior applications or wet or damp locations. Fasteners, including nuts and washers, for fire-retardant-treated wood used in exterior applications or wet or damp locations shall be of hot-dipped zinc-coated galvanized steel, stainless steel, silicon bronze or copper. Staples shall be of stainless steel. Fasteners other than nails, staples, timber rivets, wood screws and lag screws shall be permitted to be of mechanically deposited zinccoated steel with coating weights in accordance with ASTM B695, Class 55 minimum.

2304.10.6.4 Fasteners for fire-retardant-treated wood used in interior applications. Fasteners, including nuts and washers, for fire-retardant-treated wood used in interior locations shall be in accordance with the manufacturer’s recommendations. In the absence of manufacturer’s recommendations, Section 2304.10.6.3 shall apply.

2304.10.7 Load path. Where wall framing members are not continuous from the foundation sill to the roof, the members shall be secured to ensure a continuous load path. Where required, sheet metal clamps, ties or clips shall be formed of galvanized steel or other approved corrosion-resistant material not less than 0.0329-inch (0.836 mm) base metal thickness.

2304.10.8 Framing requirements. Wood columns and posts shall be framed to provide full end bearing. Alternatively, columnand-post end connections shall be designed to resist the full compressive loads, neglecting end-bearing capacity. Column-andpost end connections shall be fastened to resist lateral and net induced uplift forces.
CBC § 2304.10.2.1 High relevance — show source text
2304.10.2.1 Additional requirements. [DSA-SS and OSHPD 1, 1R, 2, 4 & 5] Fasteners used for the attachment of exterior wall coverings shall be of hot-dipped zinc-coated galvanized steel, mechanically deposited zinc-coated steel, stainless steel, silicon bronze or copper. The coating weights for hot-dipped zinc-coated fasteners shall be in accordance with ASTM A153. The coating weights for mechanically deposited zinc coated fasteners shall be in accordance with ASTM B695, Class 55 minimum.

2304.10.3 Sheathing fasteners. Sheathing nails or other approved sheathing connectors shall be driven so that their head or crown is flush with the surface of the sheathing.

2304.10.4 Joist hangers and framing anchors. Connections depending on joist hangers or framing anchors, ties and other mechanical fastenings not otherwise covered are permitted where approved. The vertical load-bearing capacity, torsional moment capacity and deflection characteristics of joist hangers shall be determined in accordance with ASTM D7147.

2304.10.5 Other fasteners. Clips, staples, glues and other approved methods of fastening are permitted where approved.

2304.10.6 Fasteners and connectors in contact with preservative-treated and fire-retardant-treated wood. Fasteners, including nuts and washers, and connectors in contact with preservative-treated and fire-retardant-treated wood shall be in accordance with Sections 2304.10.6.1 through 2304.10.6.4. The coating weights for zinc-coated fasteners shall be in accordance

2025 CALIFORNIA BUILDING CODE 23-21

on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

WOOD

with ASTM A153. The coating weight for zinc-coated nails shall be in accordance with ASTM A153 Class D or ASTM A641 Class 3S [1 ounce per square foot (305 g/m [2] )]. Stainless steel driven fasteners shall be in accordance with the material requirements of ASTM F1667.

2304.10.6.1 Fasteners and connectors for preservative-treated wood. Fasteners, including nuts and washers, in contact with preservative-treated wood shall be of hot-dipped zinc-coated galvanized steel, stainless steel, silicon bronze or copper. Staples shall be of stainless steel. Fasteners other than nails, staples, timber rivets, wood screws and lag screws shall be permitted to be of mechanically deposited zinc-coated steel with coating weights in accordance with ASTM B695, Class 55 minimum. Connectors that are used in exterior applications and in contact with preservative-treated wood shall have coating types and weights in accordance with the treated wood or connector manufacturer’s recommendations. In the absence of manufacturer’s recommendations, not less than ASTM A653, Type G185 zinc-coated galvanized steel, or equivalent, shall be used.

Exception: Plain carbon steel fasteners, including nuts and washers, in SBX/DOT and zinc borate preservative-treated wood in an interior, dry environment shall be permitted.

2304.10.6.2 Fastenings for wood foundations. Fastenings, including nuts and washers, for wood foundations shall be as required in AWC PWF.
CBC § 0.35 High relevance — show source text
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.|

2304.10.2.1 Additional requirements. [DSA-SS and OSHPD 1, 1R, 2, 4 & 5] Fasteners used for the attachment of exterior wall coverings shall be of hot-dipped zinc-coated galvanized steel, mechanically deposited zinc-coated steel, stainless steel, silicon bronze or copper. The coating weights for hot-dipped zinc-coated fasteners shall be in accordance with ASTM A153. The coating weights for mechanically deposited zinc coated fasteners shall be in accordance with ASTM B695, Class 55 minimum.

2304.10.3 Sheathing fasteners. Sheathing nails or other approved sheathing connectors shall be driven so that their head or crown is flush with the surface of the sheathing.

2304.10.4 Joist hangers and framing anchors. Connections depending on joist hangers or framing anchors, ties and other mechanical fastenings not otherwise covered are permitted where approved. The vertical load-bearing capacity, torsional moment capacity and deflection characteristics of joist hangers shall be determined in accordance with ASTM D7147.

2304.10.5 Other fasteners. Clips, staples, glues and other approved methods of fastening are permitted where approved.

2304.10.6 Fasteners and connectors in contact with preservative-treated and fire-retardant-treated wood. Fasteners, including nuts and washers, and connectors in contact with preservative-treated and fire-retardant-treated wood shall be in accordance with Sections 2304.10.6.1 through 2304.10.6.4. The coating weights for zinc-coated fasteners shall be in accordance

2025 CALIFORNIA BUILDING CODE 23-21

CBC § 2304.10.6.3 High relevance — show source text

2304.10.6.3 Fasteners for fire-retardant-treated wood used in exterior applications or wet or damp locations. Fasteners, including nuts and washers, for fire-retardant-treated wood used in exterior applications or wet or damp locations shall be of hot-dipped zinc-coated galvanized steel, stainless steel, silicon bronze or copper. Staples shall be of stainless steel. Fasteners other than nails, staples, timber rivets, wood screws and lag screws shall be permitted to be of mechanically deposited zinccoated steel with coating weights in accordance with ASTM B695, Class 55 minimum.

2304.10.6.4 Fasteners for fire-retardant-treated wood used in interior applications. Fasteners, including nuts and washers, for fire-retardant-treated wood used in interior locations shall be in accordance with the manufacturer’s recommendations. In the absence of manufacturer’s recommendations, Section 2304.10.6.3 shall apply.

2304.10.7 Load path. Where wall framing members are not continuous from the foundation sill to the roof, the members shall be secured to ensure a continuous load path. Where required, sheet metal clamps, ties or clips shall be formed of galvanized steel or other approved corrosion-resistant material not less than 0.0329-inch (0.836 mm) base metal thickness.

2304.10.8 Framing requirements. Wood columns and posts shall be framed to provide full end bearing. Alternatively, columnand-post end connections shall be designed to resist the full compressive loads, neglecting end-bearing capacity. Column-andpost end connections shall be fastened to resist lateral and net induced uplift forces.

2304.11 Heavy timber construction. Where a structure, portion thereof or individual structural elements are required by provisions of this code to be of heavy timber, the building elements therein shall comply with the applicable provisions of Sections 2304.11.1 through 2304.11.4. Minimum dimensions of heavy timber shall comply with the applicable requirements in Table 2304.11 based on roofs or floors supported and the configuration of each structural element, or in Sections 2304.11.2 through 2304.11.4. Lumber decking shall be in accordance with Section 2304.9.

TABLE 2304.11—MINIMUM DIMENSIONS OF HEAVY TIMBER STRUCTURAL MEMBERS	Col2	Col3	Col4	Col5	Col6	Col7	Col8
		MINIMUM NOMI- NAL SOLID SAWN SIZE	MINIMUM NOMI- NAL SOLID SAWN SIZE	MINIMUM GLUED- LAMINATED NET SIZE	MINIMUM GLUED- LAMINATED NET SIZE	MINIMUM STRUC- TURAL COMPOSITE LUMBER NET SIZE	MINIMUM STRUC- TURAL COMPOSITE LUMBER NET SIZE
SUPPORTING	HEAVY TIMBER STRUCTURAL ELEMENTS	Width, inch	Depth, inch	Width, inch	Depth, inch	Width, inch	**Depth,

CBC § 3.1 High relevance — show source text
Exception: Quality marks on lumber less than 1 inch (25 mm) nominal thickness, or lumber less than nominal 1 inch by 5 inches (25 mm by 127 mm) or 2 inches by 4 inches (51 mm by 102 mm) or lumber 36 inches (914 mm) or less in length shall be applied by stamping the faces of exterior pieces or by end labeling not less than 25 percent of the pieces of a bundled unit.

R304.3 Fasteners and connectors in contact with preservative-treated and fire-retardant-treated wood. Fasteners, including nuts and washers, and connectors in contact with preservative-treated wood and fire-retardant-treated wood shall be in accordance with this section. The coating weights for zinc-coated fasteners shall be in accordance with ASTM A153. The coating weight for zinccoated nails shall be in accordance with ASTM A153 Class D or ASTM A641 Class 3S. Stainless steel driven fasteners shall be in accordance with the material requirements of ASTM F1667.

R304.3.1 Fasteners for preservative-treated wood. Fasteners, including nuts and washers, for preservative-treated wood shall be of hot-dipped, zinc-coated galvanized steel, stainless steel, silicon bronze or copper. Staples shall be of stainless steel. Coating types and weights for connectors in contact with preservative-treated wood shall be in accordance with the connector manufacturer’s recommendations. In the absence of manufacturer’s recommendations, not less than ASTM A653 type G185 zinc-coated galvanized steel, or equivalent, shall be used.

Exceptions:
1. One-half-inch diameter (12.7 mm) or greater steel bolts.
2. Fasteners other than nails, staples and timber rivets shall be permitted to be of mechanically deposited zinc-coated steel with coating weights in accordance with ASTM B695, Class 55 minimum.
3. Plain carbon steel fasteners in SBX/DOT and zinc borate preservative-treated wood in an interior, dry environment shall be permitted.
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BUILDING PLANNING

R304.3.2 Fastenings for wood foundations. Fastenings, including nuts and washers, for wood foundations shall be as required in AWC PWF.

R304.3.3 Fasteners for fire-retardant-treated wood used in exterior applications or wet or damp locations. Fasteners, including nuts and washers, for fire-retardant-treated wood used in exterior applications or wet or damp locations shall be of hot-dipped, zinc-coated galvanized steel, stainless steel, silicon bronze or copper. Fasteners other than nails, staples and timber rivets shall be permitted to be of mechanically deposited zinc-coated steel with coating weights in accordance with ASTM B695, Class 55 minimum.

R304.3.4 Fasteners for fire-retardant-treated wood used in interior applications. Fasteners, including nuts and washers, for fire-retardant-treated wood used in interior locations shall be in accordance with the manufacturer’s recommendations. In the absence of the manufacturer’s recommendations, Section R304.3.3 shall apply.

R304.4 Plastic composites. Plastic composite exterior deck boards, stair treads, guards and handrails containing wood, cellulosic or other biodegradable materials shall comply with the requirements of Section R507.2.2.

SECTION R305—PROTECTION AGAINST SUBTERRANEAN TERMITES
CBC § 1.1 High relevance — show source text
R304.1.1 Field treatment. Field-cut ends, notches and drilled holes of preservative-treated wood shall be treated in the field in accordance with AWPA M4.

R304.1.2 Ground contact. All wood in contact with the ground, embedded in concrete in direct contact with the ground or embedded in concrete exposed to the weather that supports permanent structures intended for human occupancy shall be approved pressure-preservative-treated wood suitable for ground contact use, except that untreated wood used entirely below groundwater level or continuously submerged in fresh water shall not be required to be pressure-preservative treated.

R304.1.3 Ventilation required beneath balcony or elevated walking surfaces. Enclosed framing in exterior balconies and elevated walking surfaces that are exposed to rain, snow or drainage from irrigation shall be provided with openings that provide a net-free cross-ventilation area not less than [1] / 150 of the area of each separate space.

R304.2 Quality mark. Lumber and plywood required to be pressure-preservative treated in accordance with Section R304.1 shall bear the quality mark of an approved inspection agency that maintains continuing supervision, testing and inspection over the quality of the product and that has been approved by an accreditation body that complies with the requirements of the American Lumber Standard Committee treated wood program.

R304.2.1 Required information. The required quality mark on each piece of pressure-preservative-treated lumber or plywood shall contain the following information:
1. Identification of the treating plant.
2. Type of preservative.
3. The minimum preservative retention.
4. End use for which the product was treated.
5. Standard to which the product was treated.
6. Identity of the approved inspection agency.
7. The designation “Dry,” if applicable.
Exception: Quality marks on lumber less than 1 inch (25 mm) nominal thickness, or lumber less than nominal 1 inch by 5 inches (25 mm by 127 mm) or 2 inches by 4 inches (51 mm by 102 mm) or lumber 36 inches (914 mm) or less in length shall be applied by stamping the faces of exterior pieces or by end labeling not less than 25 percent of the pieces of a bundled unit.

R304.3 Fasteners and connectors in contact with preservative-treated and fire-retardant-treated wood. Fasteners, including nuts and washers, and connectors in contact with preservative-treated wood and fire-retardant-treated wood shall be in accordance with this section. The coating weights for zinc-coated fasteners shall be in accordance with ASTM A153. The coating weight for zinccoated nails shall be in accordance with ASTM A153 Class D or ASTM A641 Class 3S. Stainless steel driven fasteners shall be in accordance with the material requirements of ASTM F1667.

R304.3.1 Fasteners for preservative-treated wood. Fasteners, including nuts and washers, for preservative-treated wood shall be of hot-dipped, zinc-coated galvanized steel, stainless steel, silicon bronze or copper. Staples shall be of stainless steel. Coating types and weights for connectors in contact with preservative-treated wood shall be in accordance with the connector manufacturer’s recommendations. In the absence of manufacturer’s recommendations, not less than ASTM A653 type G185 zinc-coated galvanized steel, or equivalent, shall be used.
CBC § 3-34 High relevance — show source text
3-34 2025 CALIFORNIA RESIDENTIAL CODE

on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.

BUILDING PLANNING

R304.3.2 Fastenings for wood foundations. Fastenings, including nuts and washers, for wood foundations shall be as required in AWC PWF.

R304.3.3 Fasteners for fire-retardant-treated wood used in exterior applications or wet or damp locations. Fasteners, including nuts and washers, for fire-retardant-treated wood used in exterior applications or wet or damp locations shall be of hot-dipped, zinc-coated galvanized steel, stainless steel, silicon bronze or copper. Fasteners other than nails, staples and timber rivets shall be permitted to be of mechanically deposited zinc-coated steel with coating weights in accordance with ASTM B695, Class 55 minimum.

R304.3.4 Fasteners for fire-retardant-treated wood used in interior applications. Fasteners, including nuts and washers, for fire-retardant-treated wood used in interior locations shall be in accordance with the manufacturer’s recommendations. In the absence of the manufacturer’s recommendations, Section R304.3.3 shall apply.

R304.4 Plastic composites. Plastic composite exterior deck boards, stair treads, guards and handrails containing wood, cellulosic or other biodegradable materials shall comply with the requirements of Section R507.2.2.

SECTION R305—PROTECTION AGAINST SUBTERRANEAN TERMITES

R305.1 Subterranean termite control methods. In areas subject to damage from termites as indicated by Table R301.2, protection shall be by one, or a combination, of the following methods:
1. Chemical termiticide treatment in accordance with Section R305.2.
2. Termite-baiting system installed and maintained in accordance with the label.
3. Pressure-preservative-treated wood in accordance with the provisions of Section R304.1.
4. Naturally durable termite-resistant wood.
5. Physical barriers in accordance with Section R305.3 and used in locations as specified in Section R304.1.
6. Cold-formed steel framing in accordance with Sections R505.2.1 and R603.2.1.
R305.1.1 Quality mark. Lumber and plywood required to be pressure-preservative treated in accordance with Section R305.1 shall bear the quality mark of an approved inspection agency that maintains continuing supervision, testing and inspection over the quality of the product and that has been approved by an accreditation body that complies with the requirements of the American Lumber Standard Committee treated wood program.

R305.1.2 Field treatment. Field-cut ends, notches and drilled holes of pressure-preservative-treated wood shall be retreated in the field in accordance with AWPA M4.

R305.2 Chemical termiticide treatment. Chemical termiticide treatment shall include soil treatment or field-applied wood treatment. The concentration, rate of application and method of treatment of the chemical termiticide shall be in strict accordance with the termiticide label.

R305.3 Barriers. Approved physical barriers, such as metal or plastic sheeting or collars specifically designed for termite prevention, shall be installed in a manner to prevent termites from entering the structure. Shields placed on top of an exterior foundation wall shall be used only if in combination with another method of protection.
CBC § 2308.10 Medium relevance — show source text
walls 2308.10 Calculated fire resistance 722.6 Ceiling framing 2308.11 Connectors and fasteners 2304.10,

2308.5

Contacting concrete, masonry or earth 2304.12.1.3, 2304.12.1.4, 2304.12.2.1, 2304.12.2.2, 2304.12.2.6 Cross-laminated timber 2301.2, 2303.1, 2303.1.4, 2304.11.2.1, 2304.11.3.1, 2304.11.4.1 Cutting, notching and boring of dimensional wood framing 2308.6 Decay, protection against 2304.12 Diaphragms 2305.1, 2305.2, 2306.2 Dimensions 2301.2 Draftstopping 718.3, 718.4 End-jointed lumber 2303.1.1.2 Fiberboard 2303.1.6, Table 2306.3(2) Fireblocking 718.2 Fire-retardant treated 2303.2 Floor and roof framing (see Floor Construction, Wood) 2304.4 Floor sheathing 2304.8 Foundation 1807.1.4, 2304.10.6.2, 2304.12.1.2, 2308.10.8.1, 2308.7 Grade, lumber 2303.1.1

INDEX-22 2025 CALIFORNIA BUILDING CODE

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INDEX

Hardboard 2303.1.7 Heavy timber construction 602.4, 2304.11

Hurricane shutters 1609.2

I-joist 2303.1.2 Inspection, special 1705.12.1, 1705.13.2, 1705.5 Lateral force-resisting systems 2305 Light-frame construction, conventional 2308 Load and resistance factor design 2307

Moisture content 2303.1.9.2, 2303.2.9, 2303.7, 2304.9.5.1, Table 2305.2(1), Table 2305.2(2) Nails and staples 2303.6 Plywood, hardwood 2303.3 Preservative treated 1402.6, 1402.9,

2303.1.9 Roof framing (see Roof Construction, Wood)

2304.4 Roof sheathing 2304.8 Seismic provisions 2305, 2306, 2308.10.10, 2308.10.6, 2308.10.8 Shear walls 2305, 2306.3 Standards and quality, minimum 2303 Structural panels 2303.1.5 Supporting concrete or masonry 2304.13 Termite, protection against 2304.12 Trusses 2303.4

Veneer Chapter 14 Wall framing (see Wall, Wood Construction)

2304.3 Wall sheathing, exterior 2304.6 Wood Frame Construction Manual
CBC § 2.1 Medium relevance — show source text
R507.2 Materials. Materials used for the construction of decks shall comply with this section.

R507.2.1 Wood materials. Wood structural members shall be protected from decay where required by Sections R304.1 and R304.1.2, and protected from termites where required by Section R305.1. Where design in accordance with Section R301 is provided, wood structural members shall be designed using the wet service factor defined in AWC NDS. Sawn lumber for joists, beams and posts shall be No. 2 or better. Cuts, notches and drilled holes of preservative-treated wood members shall be treated in accordance with Section R304.1.1.

R507.2.1.1 Engineered wood products. Engineered wood products shall be in accordance with Section R502.

R507.2.2 Plastic composite deck boards, stair treads, guards or handrails. Plastic composite exterior deck boards, stair treads, guards and handrails shall comply with the requirements of ASTM D7032 and this section.

R507.2.2.1 Labeling. Plastic composite deck boards and stair treads, or their packaging, shall bear a label that indicates compliance with ASTM D7032 and includes the allowable load and maximum allowable span determined in accordance with ASTM D7032. Plastic or composite handrails and guards, or their packaging, shall bear a label that indicates compliance with ASTM D7032 and includes the maximum allowable span determined in accordance with ASTM D7032.

R507.2.2.2 Flame spread index. Plastic composite deck boards, stair treads, guards, and handrails shall exhibit a flame spread index not exceeding 200 when tested in accordance with ASTM E84 or UL 723 with the test specimen remaining in place during the test.

Exception: Plastic composites determined to be noncombustible.

R507.2.2.3 Decay resistance. Plastic composite deck boards, stair treads, guards and handrails containing wood, cellulosic or other biodegradable materials shall be decay resistant in accordance with ASTM D7032.

R507.2.2.4 Termite resistance. Where required by Section 305, plastic composite deck boards, stair treads, guards and handrails containing wood, cellulosic or other biodegradable materials shall be termite resistant in accordance with ASTM D7032.

R507.2.2.5 Installation of plastic composites. Plastic composite deck boards, stair treads, guards and handrails shall be installed in accordance with this code and the manufacturer’s instructions.

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FLOORS

R507.2.3 Fasteners and connectors. Metal fasteners and connectors used for all decks shall be in accordance with Section R304.3 and Table R507.2.3. Holes for through bolts shall be drilled to a diameter of [1] / 32 inch to [1] / 16 inch larger than the bolt diameter. Connectors shall be installed in accordance with the manufacturer’s approved instructions.

|TABLE R507.2.3—FASTENER AND CONNECTOR SPECIFICATIONS FOR DECKSa,
CBC § 1404.2 Medium relevance — show source text
Weather Protection

Exterior walls 1404.2

Roofs 1503 Welding Materials, verification of steel reinforcement 1705.3.2 Special inspections 1705.13.3, 1705.2, 1705.3.1 Splices of reinforcement in masonry 2107.3, 2108.3 Wildland-Urban Interface 101.4.8

Wind Load 1609 Basic design wind speed 1609.3 Construction documents

107, 1603.1.4 Exposure category 1609.4 Glazing 1609.2, 2404 Hurricane 1507.1.1 Masonry, empirical design 2109.1.1 Nominal design wind speed 1609.3.1 Roofs 1504.1, 1609.6, 2308.11.4 Seismic detailing required 1604.10 Special inspection 1705.12 Statement of special inspections 1704.3 Wind design geodatabase 1609.3 Wind tunnel testing 1504.3.1.2, 1609.1.1 Winders, stair (see Stairway Construction) Window Accessibility 11B-229 Emergency egress 1031 Exterior, structural testing 1709.5 Fire (see Opening Protectives) 716.2, 716.2.8 Glass (see Glazing) 1404.14 Guards 1015.8 Required light 1204.1, 1204.2 Wells 1031.6 Wires, Penetration Protection 714 Wood Chapter 23 Allowable stress design 2306 Bracing, walls 2308.10 Calculated fire resistance 722.6 Ceiling framing 2308.11 Connectors and fasteners 2304.10,

2308.5

Contacting concrete, masonry or earth 2304.12.1.3, 2304.12.1.4, 2304.12.2.1, 2304.12.2.2, 2304.12.2.6 Cross-laminated timber 2301.2, 2303.1, 2303.1.4, 2304.11.2.1, 2304.11.3.1, 2304.11.4.1 Cutting, notching and boring of dimensional wood framing 2308.6 Decay, protection against 2304.12 Diaphragms 2305.1, 2305.2, 2306.2 Dimensions 2301.2 Draftstopping 718.3, 718.4 End-jointed lumber 2303.1.1.2 Fiberboard 2303.1.6, Table 2306.3(2) Fireblocking 718.2 Fire-retardant treated 2303.2 Floor and roof framing (see Floor Construction, Wood) 2304.4 Floor sheathing 2304.8 Foundation 1807.1.4, 2304.10.6.2, 2304.12.1.2, 2308.10.8.1, 2308.7 Grade, lumber 2303.1.1

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CBC § 1202.2. Medium relevance — show source text

Where 1-inch by 4-inch (25 mm by 102 mm) spaced sheathing is installed at 10 inches (254 mm) on center, additional 1-inch by 4-inch (25 mm by 102 mm) boards shall be installed between the sheathing boards. 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 Section 1202.2. 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.

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ROOF ASSEMBLIES AND ROOFTOP STRUCTURES

1507.9.1.1 Solid sheathing required. Solid sheathing is required in areas where the average daily temperature in January is 25°F (-4°C) or less or where there is a possibility of ice forming along the eaves causing a backup of water.

1507.9.2 Deck slope. Wood shakes shall only be used on slopes of not less than 4 units vertical in 12 units horizontal (33-percent slope).

1507.9.3 Underlayment. Underlayment shall comply with Section 1507.1.1.

1507.9.4 Ice barrier. Where required, ice barriers shall comply with Section 1507.1.2.

1507.9.5 Interlayment. Interlayment shall comply with ASTM D226, Type I.

1507.9.6 Material standards. Wood shakes shall comply with the requirements of Table 1507.9.6.

TABLE 1507.9.6—WOOD SHAKE MATERIAL REQUIREMENTS	Col2	Col3
MATERIAL	MINIMUM GRADES	APPLICABLE GRADING RULES
Wood shakes of naturally durable wood	1	CSSB
Taper sawn shakes of naturally durable wood	1 or 2	CSSB
Preservative-treated shakes and shingles of naturally durable wood	1	CSSB
Fire-retardant-treated shakes and shingles of naturally durable wood	1	CSSB
Preservative-treated taper sawn shakes of Southern pine treated in accor- dance with AWPA U1 (Commodity Specification A, Special Requirement 4.6)	1 or 2	TFS
CSSB = Cedar Shake and Shingle Bureau. TFS = Forest Products Laboratory of the Texas Forest Services.	CSSB = Cedar Shake and Shingle Bureau. TFS = Forest Products Laboratory of the Texas Forest Services.	CSSB = Cedar Shake and Shingle Bureau. TFS = Forest Products Laboratory of the Texas Forest Services.

1507.9.7 Attachment. Fasteners for wood shakes shall be corrosion resistant with a minimum penetration of [3] / 4 inch (19.1 mm) into the sheathing. For sheathing less than [1] / 2 inch (12.7 mm) in thickness, the fasteners shall extend through the sheathing. Each shake shall be attached with not fewer than two fasteners.

CBC § 25.4 Medium relevance — show source text

Foam sheathing shall have a minimum compressive strength of 15 pounds per square inch in accordance with ASTM C578 or ASTM C1289.|For SI: 1 inch = 25.4 mm, 1 pound per square foot (psf) = 0.0479 kPa, 1 pound per square inch = 0.00689 MPa.
DR = design required, o.c. = on center.
a. Cold-formed steel framing shall be minimum 33 ksi steel for 33 mil and 43 mil steel and 50 ksi steel for 54 mil steel or thicker.
b. Screws shall comply with the requirements of AISI S240.
c. Foam sheathing shall have a minimum compressive strength of 15 pounds per square inch in accordance with ASTM C578 or ASTM C1289.|

[BS] 1404.5.2.2 Furred cladding attachment. Where steel or wood furring is used to attach cladding over foam sheathing, furring minimum fastening requirements to support the cladding weight shall be as specified in Table 1404.5.2.2. Where placed horizontally, wood furring shall be preservative-treated wood in accordance with Section 2303.1.9 or naturally durable wood and fasteners shall be corrosion resistant in accordance Section 2304.10.6. Steel furring shall have a minimum G60 galvanized coating.

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EXTERIOR WALLS

[BS] TABLE 1404.5.2.2—FURRING MINIMUM FASTENING REQUIREMENTS FOR APPLICATION OVER FOAM PLASTIC SHEATHING TO SUPPORT CLADDING WEIGHTa	Col2	Col3	Col4	Col5	Col6	Col7	Col8	Col9	Col10	Col11	Col12	Col13
FURRING MATERIAL	FRAMING MEMBER	FASTENER TYPE AND MINIMUM SIZEb	MINIMUM PENETRATION INTO WALL FRAMING (inches)	FASTENER SPACING IN FURRING (inches)	MAXIMUM THICKNESS OF FOAM SHEATHINGd (inches)	MAXIMUM THICKNESS OF FOAM SHEATHINGd (inches)	MAXIMUM THICKNESS OF FOAM SHEATHINGd (inches)	MAXIMUM THICKNESS OF FOAM SHEATHINGd (inches)	MAXIMUM THICKNESS OF FOAM SHEATHINGd (inches)	MAXIMUM THICKNESS OF FOAM SHEATHINGd (inches)	MAXIMUM THICKNESS OF FOAM SHEATHINGd (inches)	MAXIMUM THICKNESS OF FOAM SHEATHINGd (inches)
FURRING MATERIAL	FRAMING MEMBER	FASTENER TYPE AND MINIMUM SIZEb	MINIMUM PENETRATION **INTO

Frequently asked questions

Do the CBC sections mandate stainless steel for all exterior treated‑wood connections?

No. The CBC allows hot‑dipped zinc‑coated galvanize, stainless steel, silicon bronze or copper for treated and FR wood in exterior/wet locations; stainless is required for staples and is a common choice when higher corrosion resistance is needed. § 2304.10.6.1 § 2304.10.6.3

Can I use electrogalvanized (mechanically deposited zinc) nails?

Mechanically deposited zinc (ASTM B695 Class 55 minimum) is permitted for fasteners other than nails, staples, timber rivets, wood screws and lag screws; nails and staples are treated separately and the code points to ASTM A153 for driven‑fastener coating weights. § 2304.10.6.1 § 2304.10.6

If the FR‑wood manufacturer gives no guidance, what do I do for interior FR wood?

If no manufacturer recommendations exist for interior fire‑retardant‑treated wood, the code requires you to use the same materials called for in § 2304.10.6.3 (the exterior/wet‑location list). § 2304.10.6.4

Does the CBC specify the exact stainless steel alloy to use?

No. The sections retrieved require “stainless steel” but do not specify alloy grades (e.g., 304 vs 316). The code defers to standards and manufacturer guidance for material specifics. § 2304.10.6.1 § 2304.10.6.4

Where does the code point me for minimum zinc coating weights?

The CBC requires zinc coating weights for hot‑dipped fasteners to comply with ASTM A153 and references ASTM A153 Class D or ASTM A641 Class 3S for nails (approximately 1 oz/ft2). § 2304.10.6

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Related in the CBC

Sheathing, decking and panel application requirements (nailing, span, orientation)

Protection against decay and subterranean termites

Construction Practices & Fastening

California Building Code