CRC · California Residential Code
How must wood be protected against decay and subterranean termites?
If any wood in your house is close to exposed ground or exposed to weather (e.g., joists <18", girders <12", columns <8", siding <6"), the California Residential Code requires you use naturally durable species or preservative‑treated wood and, where termites are a hazard, also provide one of the approved termite protections (chemical treatment, baiting, treated wood, durable species, physical barriers, or steel framing). See §§ R304.1 and R305.1 for the controlling requirements and follow the fastener, marking, and field‑treatment rules referenced there.
Last reviewed: July 6, 2026
What the code requires — in plain English
The California Residential Code requires that wood exposed to ground or weather be either naturally durable or preservative-treated where listed locations and clearances are exceeded — see § R304.1.
Where termite damage is possible, the CRC requires protection by one or a combination of methods: chemical soil treatment, baiting systems, pressure‑preservative‑treated wood, naturally termite‑resistant wood, approved physical barriers, or cold‑formed steel framing — see § R305.1.
The most important rule: Where wood is close to exposed ground or exposed to the weather the CRC makes you use either naturally durable wood or preservative treatment — and where termites are a hazard you must provide one of the approved termite-protection methods. (See § R304.1 and § R305.1.)
Requirements in detail
Locations that require decay protection (clearances and what to protect)
The CRC lists specific clearances and building elements that must be of naturally durable or preservative‑treated wood. Key thresholds you must watch for are bolded below and summarized in the table that follows. See § R304.1.
- Wood joists or the bottom of a wood structural floor in crawl/unexcavated areas when closer than 18 inches to exposed ground.
- Wood girders when closer than 12 inches to exposed ground.
- Wood columns when closer than 8 inches to exposed ground.
- Wood framing or columns that rest directly on concrete or masonry exterior foundation walls and are less than 8 inches from exposed ground.
- Wood siding, sheathing and wall framing on exteriors with clearance less than 6 inches from the ground or less than 2 inches above horizontal concrete steps/porches.
- Ends of wood girders entering masonry/concrete walls with clearances less than 1/2 inch on top/side/end.
- Wood columns in contact with basement slabs unless supported on concrete piers/metal pedestals that project not less than 1 inch above the slab.
| Element / condition | Decision threshold (must protect) | Typical protection option(s) | Code Reference |
|---|---|---|---|
| Floor joists / bottom of wood structural floor (crawl or unexcavated area) | < 18 in to exposed ground | Naturally durable species or preservative-treated wood | § R304.1.1 |
| Wood girders | < 12 in to exposed ground | Naturally durable species or preservative-treated wood | § R304.1.1 |
| Wood columns | < 8 in to exposed ground | Naturally durable species or preservative-treated wood | § R304.1.1 |
| Wood framing on exterior foundation walls | < 8 in from exposed ground | Naturally durable or preservative-treated wood | § R304.1.2 |
| Siding/sheathing/wall framing (exterior) | < 6 in from ground or < 2 in above concrete steps/slabs | Naturally durable or preservative-treated wood | § R304.1.5 |
| Ends of girders entering concrete/masonry | Clearance < 1/2 in | Treated or naturally durable wood | § R304.1.4 |
| Columns on basement floor slabs | Contact with slab unless on piers/pedestals ≥ 1 in above slab | Support on concrete piers/metal pedestals or use treated wood | § R304.1.9 |
(Paraphrased; see § R304.1 for full list and exact wording.)
Methods approved for termite protection
Where the area is subject to termite damage (per CRC maps and local determinations), the code requires one or a combination of these methods — § R305.1: chemical termiticide soil treatment (follow label and § R305.2), termite baiting systems (label), pressure‑preservative‑treated wood (see R304.1), naturally durable termite‑resistant wood, approved physical barriers (see § R305.3), or cold‑formed steel framing (per R505.2.1 / R603.2.1).
- Chemical termiticide treatments must follow the product label and the code’s § R305.2 requirements (concentration, rate, method).
- Pressure‑preservative‑treated lumber required by R305.1 must bear an inspection/quality mark from an approved agency and field‑cut ends, notches and holes in treated wood must be retreated in the field in accordance with AWPA M4 (see § R305.1.1 and § R305.1.2).
- Approved physical barriers (metal/plastic sheeting, collars) must be installed to prevent termite entry; shields on top of exterior foundation walls are acceptable only when used in combination with another method. See § R305.3.
Fasteners and connectors with treated wood
Fasteners and connectors that contact preservative‑treated or fire‑retardant‑treated wood must be corrosion‑resistant materials (hot‑dipped galvanized, stainless steel, silicon bronze or copper) or as specified by the manufacturer; see § R304.3.
Plastic composites and decks
When plastic composite deck boards, stair treads, guards and handrails contain wood or other biodegradable materials and termite protection is required by Section 305, they must be termite resistant in accordance with ASTM D7032 — see § R507.2.2.4 (references R305).
Exceptions & special cases
- The code allows a geographic exception where local climatic conditions make preservative treatment unnecessary for exposed structures — see the exception in § R304.1.
- Metal shields placed on top of an exterior foundation wall are usable only if combined with another termite protection method (they are not a lone solution) — see § R305.3.
- For field treatment: any field‑cut ends, notches or drilled holes in pressure‑treated wood must be retreated per AWPA M4 as required by § R305.1.2.
If your situation involves unusual building types (e.g., intermodal shipping container floors, decks over “very heavy” termite areas), the CRC refers you to additional, specific provisions — check the related sections listed below.
Common mistakes
- Assuming any treated lumber fixes all problems — you must use the correct type of preservative for the intended location and retreat field cuts (see § R305.1.2).
- Forgetting fastener compatibility — plain carbon steel can corrode quickly in contact with many treatments; use the materials listed in § R304.3.
- Placing a metal shield as the only termite protection — shields alone are not sufficient unless combined with another approved method per § R305.3.
- Allowing exterior wood less than 6 in above grade or 2 in above slabs without treatment — these clearances trigger protection under § R304.1.
- Using improperly labeled treated lumber — required preservative-treated lumber must bear the approved quality mark per § R305.1.1.
Worked example
Scenario: A new single‑family house on a lot in a known termite area. You have an exterior sill plate on a concrete foundation and wood floor joists over a crawlspace.
- The crawlspace finished ground is 14 inches below the underside of the floor joists. Because that clearance is less than 18 inches, the floor joists must be preservative‑treated or naturally durable under § R304.1.
- The sill plate sits 6 inches above exposed ground at the foundation perimeter. Since it is less than 8 inches from exposed ground for framing members that rest on the foundation wall, that sill must be preservative‑treated or naturally durable per § R304.1.
- Because the property is in a termite‑susceptible area, you must also choose one of the methods in § R305.1 — for example, you could specify pressure‑preservative‑treated sill and joists (which must bear the required quality mark per § R305.1.1) and perform careful field retreatment of any cuts per § R305.1.2, or you could install a chemical soil termiticide per label and § R305.2.
Concrete actions for the example:
- Specify AWPA U1‑compliant above‑ground or soil‑use treatment as appropriate (match end‑use). Marking and documentation required per § R305.1.1.
- Use hot‑dipped galvanized or stainless fasteners where they contact treated wood as required by § R304.3.
Related provisions (quick list)
- § R304.3 — Fasteners and connectors in contact with preservative‑treated and fire‑retardant‑treated wood (corrosion resistance).
- § R305.2 — Chemical termiticide treatment (follow product label and code).
- § R305.3 — Approved physical barriers and installation limitations (shields require combination).
- § R507.2.1 / R507.2.2.4 — Deck materials; decay and termite resistance requirements for plastic composites and deck members (references R304/R305).
- § R305.1.1 / § R305.1.2 — Quality mark & field retreatment requirements for pressure‑treated lumber.
- See the termite‑infestation probability map and related text referenced by the CRC for area determinations (Figure R305.4 is referenced in the code).
Code references
Grounded in the retrieved California Residential Code — click a citation to read the verbatim passage:
CRC § 3-34 High relevance — show source text
3-34 2025 CALIFORNIA RESIDENTIAL CODE
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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
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:
Chemical termiticide treatment in accordance with Section R305.2.
Termite-baiting system installed and maintained in accordance with the label.
Pressure-preservative-treated wood in accordance with the provisions of Section R304.1.
Naturally durable termite-resistant wood.
Physical barriers in accordance with Section R305.3 and used in locations as specified in Section R304.1.
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.
CRC § 3-33 High relevance — show source text
R304 Protection of Wood and Wood-Based Products
Against Decay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-33
R305 Protection Against Subterranean Termites. . . . . . . 3-35
R306 Flood-Resistant Construction. . . . . . . . . . . . . . . . . . . 3-36
R307 Storm Shelters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40
R308 Site Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40
R309 Automatic Sprinkler Systems . . . . . . . . . . . . . . . . . . . 3-41
R310 Smoke Alarms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-54
R311 Carbon Monoxide Alarms. . . . . . . . . . . . . . . . . . . . . . . 3-58
R312 Minimum Room Areas . . . . . . . . . . . . . . . . . . . . . . . . . 3-59
R313 Ceiling Height . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-59
R314 Mezzanines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-60
R315 Sleeping Lofts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-60
R316 Habitable Attics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-61
R317 Garages and Carports. . . . . . . . . . . . . . . . . . . . . . . . . . 3-61
R318 Means of Egress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-62
R319 Emergency Escape and Rescue Openings . . . . . . . . 3-65
R320 Handrails . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-67
R321 Guards and Window Fall Protection . . . . . . . . . . . . . 3-67
R322 Accessibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-68
R323 Elevators and Platform Lifts . . . . . . . . . . . . . . . . . . . . 3-68
R324 Glazing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-68
CRC § 2-5 High relevance — show source text
Part II—Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2-5
CHAPTER 2 DEFINITIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . .2-5
R201 General. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
R202 Definitions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5
Part III—Building Planning and Construction . . . . . . . . . . . .3-5
CHAPTER 3 BUILDING PLANNING . . . . . . . . . . . . . . . . . . . . .3-5
R300 Site Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
R301 Design Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5
R302 Fire-Resistant Construction . . . . . . . . . . . . . . . . . . . . 3-23
R303 Foam Plastic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-31
R304 Protection of Wood and Wood-Based Products
Against Decay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-33
R305 Protection Against Subterranean Termites. . . . . . . 3-35
R306 Flood-Resistant Construction. . . . . . . . . . . . . . . . . . . 3-36
R307 Storm Shelters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40
R308 Site Address . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-40
R309 Automatic Sprinkler Systems . . . . . . . . . . . . . . . . . . . 3-41
R310 Smoke Alarms. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-54
R311 Carbon Monoxide Alarms. . . . . . . . . . . . . . . . . . . . . . . 3-58
R312 Minimum Room Areas . . . . . . . . . . . . . . . . . . . . . . . . . 3-59
R313 Ceiling Height . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-59
CRC § 2.1 High 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,
CRC § 3.1 High relevance — show source text
Cold-formed steel framing shall be anchored directly to the foundation or fastened to wood sill plates in accordance with Section R505.3.1 or R603.3.1, as applicable. Wood sill plates supporting cold-formed steel framing shall be anchored to the foundation in accordance with this section.
Wood sole plates at all exterior walls on monolithic slabs, wood sole plates of braced wall panels at building interiors on monolithic slabs and all wood sill plates shall be anchored to the foundation with minimum [1] / 2 -inch-diameter (12.7 mm) anchor bolts spaced not greater than 6 feet (1829 mm) on center or approved anchors or anchor straps spaced as required to provide equivalent anchorage to [1] / 2 -inch-diameter (12.7 mm) anchor bolts. Bolts shall extend not less than 7 inches (178 mm) into concrete or grouted cells of concrete masonry units. The bolts shall be located in the middle third of the width of the plate. A nut and washer shall be tightened on each anchor bolt. There shall be not fewer than two bolts per plate section with one bolt located not more than 12 inches (305 mm) or less than seven bolt diameters from each end of the plate section. Interior bearing wall sole plates on monolithic slab foundation that are not part of a braced wall panel shall be positively anchored with approved fasteners. Sill plates and sole plates shall be protected against decay and termites where required by Sections R304 and R305. Anchor bolts shall be permitted to be located while concrete is still plastic and before it has set. Where anchor bolts resist placement or the consolidation of concrete around anchor bolts is impeded, the concrete shall be vibrated to ensure full contact between the anchor bolts and concrete.
Exceptions:
- Walls 24 inches (610 mm) total length or shorter connecting offset braced wall panels shall be anchored to the foundation with not fewer than one anchor bolt located in the center third of the plate section and shall be attached to adjacent braced wall panels at corners as shown in Item 9 of Table R602.3(1).
- Connection of walls 12 inches (305 mm) total length or shorter connecting offset braced wall panels to the foundation without anchor bolts shall be permitted. The wall shall be attached to adjacent braced wall panels at corners as shown in Item 9 of Table R602.3(1).
R403.1.6.1 Foundation anchorage in Seismic Design Categories C, D 0 , D 1 and D 2 . In addition to the requirements of Section R403.1.6, the following requirements shall apply to wood light-frame structures in Seismic Design Categories D 0, D 1 and D 2 and wood light-frame townhouses in Seismic Design Category C.
- Plate washers conforming to Section R602.11.1 shall be provided for all anchor bolts over the full length of required braced wall lines except where approved anchor straps are used. Properly sized cut washers shall be permitted for anchor bolts in wall lines not containing braced wall panels.
- Interior braced wall plates shall have anchor bolts spaced at not more than 6 feet (1829 mm) on center and located within 12 inches (305 mm) of the ends of each plate section where supported on a continuous foundation.
- Interior bearing wall sole plates shall have anchor bolts spaced at not more than 6 feet (1829 mm) on center and located within 12 inches (305 mm) of the ends of each plate section where supported on a continuous foundation.
CRC § 12.7 High relevance — show source text
R303.8 Wind resistance. Foam plastic insulation complying with ASTM C578 and ASTM C1289 and used as exterior wall sheathing on framed wall assemblies shall comply with ANSI/ABTG FS 100 for wind pressure resistance unless installed directly over or under a sheathing material that is separately capable of resisting the wind load or otherwise exempted from the scope of ANSI/ABTG FS 100.
SECTION R304—PROTECTION OF WOOD AND WOOD-BASED PRODUCTS AGAINST DECAY
R304.1 Location required. Protection of wood and wood-based products from decay shall be provided in the following locations by the use of naturally durable wood or wood that is preservative-treated in accordance with AWPA U1.
- In crawl spaces or unexcavated areas located within the periphery of the building foundation, wood joists or the bottom of a wood structural floor where closer than 18 inches (457 mm) to exposed ground, wood girders where closer than 12 inches (305 mm) to exposed ground, and wood columns where closer than 8 inches (204 mm) to exposed ground.
- Wood framing members, including columns, that rest directly on concrete or masonry exterior foundation walls and are less than 8 inches (203 mm) from the exposed ground.
- Sills and sleepers on a concrete or masonry slab that is in direct contact with the ground unless separated from such slab by an impervious moisture barrier.
- The ends of wood girders entering exterior masonry or concrete walls having clearances of less than [1] / 2 inch (12.7 mm) on tops, sides and ends.
2025 CALIFORNIA RESIDENTIAL CODE 3-33
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BUILDING PLANNING
Wood siding, sheathing and wall framing on the exterior of a building having a clearance of less than 6 inches (152 mm) from the ground or less than 2 inches (51 mm) measured vertically from concrete steps, porch slabs, patio slabs and similar horizontal surfaces exposed to the weather.
Wood structural members supporting moisture-permeable floors or roofs that are exposed to the weather, such as concrete or masonry slabs, unless separated from such floors or roofs by an impervious moisture barrier. The impervious moisture barrier system protecting the structure supporting floors shall provide positive drainage of water that infiltrates the moisture- permeable floor topping.
Wood furring strips or other wood framing members attached directly to the interior of exterior masonry walls or concrete walls below grade except where an approved vapor retarder is applied between the wall and the furring strips or framing members.
Portions of wood structural members that form the structural supports of buildings, decks, balconies, porches or similar permanent building appurtenances where those members are exposed to the weather without adequate protection from a roof, eave, overhang or other covering that prevents moisture or water accumulation on the surface or at joints between members. Exception: Sawn lumber used in structures located in a geographical region where experience has demonstrated that climatic conditions preclude the need to use naturally durable or preservative-treated wood where the structure is exposed to the weather.
Wood columns in contact with basement floor slabs unless supported by concrete piers or metal pedestals projecting not less than 1 inch (25 mm) above the concrete floor and separated from the concrete pier by an impervious moisture barrier.
CRC § 2.3 High relevance — show source text
SIP R610.8
Steel R603.6
Wood R602.7
Hearth R1001.9
Extension R1001.10, R1001.9
Heaters
Masonry R1002 Heating Required R325.8 Height Ceiling R313 Mezzanines R314.2 Sleeping lofts R315.3 Hollow-Unit Masonry (see Masonry)
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INDEX
Roof shingles R905.4 Methods Water distribution pipe sizing Appendix CF Mezzanines (see also Sleeping Lofts) R314, R321 Modifications R104.2.3 Moisture Content, Building Materials R109.1.4.1
Moisture Control R702.7
Mortar
Joints R606.3.1 Multiple Flues R1003.13
Natural Light (see Light) Natural Ventilation (see Ventilation) Notching Steel joists R505.2.5, R505.3.5, R804.2.5, R804.3.3 Steel studs R603.2.6, R603.3.4 Wood joists R502.8, R802.7.1 Wood studs R602.6 Wood top plates R602.6.1
Opening Protection R302.5
Parapets R302.2.2, R606.4.4 Particleboard
Floor R503.3
Walls R605 Patio Covers Appendix BF Penetrations R302.4, R302.5 Permits 1.8.4, R105, R105.5.1 Permit fees Appendix AB Photovoltaic Panel Systems R907 Ground-mounted definition R202
Photovoltaic Support Structure, Elevated R202, R324.8, R324.8.1, R324.8.2 Piers R606.7
Masonry R404.1.9 Planning Building Chapter 3 Plans R106
Plaster
Exterior R703.7
Interior R702.2
Platform Lifts R323.2, R323.3 Plumbing Fixture clearances R327
Fixtures R326, R327 Inspection 109.1.2 Requirements and definitions R202 System, definition R202 Plywood Application R703.5 Materials, walls R604
Precast Concrete
Footings R403.4 Foundation material R402.3.1
Foundation walls R404.5
Protection Against decay and termites R304, R305 Against radon Appendix BE Public Way R318.1, R319.1 Purlins R802.4.5
Hot Tubs (see Swimming Pools) R324.3.1, R328 Hurricane (see Storm Shelter)
Impact Protective System Energy storage system R330.8 Flood R306.1.4.2, R306.3.3 Human impact R324.3 Storm shelter R307.2.1
CRC § 8.4 High relevance — show source text
Floor R503.3
Walls R605 Patio Covers Appendix BF Penetrations R302.4, R302.5 Permits 1.8.4, R105, R105.5.1 Permit fees Appendix AB Photovoltaic Panel Systems R907 Ground-mounted definition R202
Photovoltaic Support Structure, Elevated R202, R324.8, R324.8.1, R324.8.2 Piers R606.7
Masonry R404.1.9 Planning Building Chapter 3 Plans R106
Plaster
Exterior R703.7
Interior R702.2
Platform Lifts R323.2, R323.3 Plumbing Fixture clearances R327
Fixtures R326, R327 Inspection 109.1.2 Requirements and definitions R202 System, definition R202 Plywood Application R703.5 Materials, walls R604
Precast Concrete
Footings R403.4 Foundation material R402.3.1
Foundation walls R404.5
Protection Against decay and termites R304, R305 Against radon Appendix BE Public Way R318.1, R319.1 Purlins R802.4.5
Hot Tubs (see Swimming Pools) R324.3.1, R328 Hurricane (see Storm Shelter)
Impact Protective System Energy storage system R330.8 Flood R306.1.4.2, R306.3.3 Human impact R324.3 Storm shelter R307.2.1
Windborne debris R301.2.1.2 Indirectly Conditioned Space (see Conditioned Space) Inflatable Amusement Device
Defined R202
Inlet To masonry chimneys R1003.16 Inspection On-site 1.8.4, R109.1 Insulation
Above-deck R906 Flame spread R302.10 Foam plastic R303 Interior
Lath R702.2.3
Other finishes R702.5
Plaster R702.2 Wall covering Chapter 7 Intermodal Shipping Container R301.1.4
Joist
Bearing R502.6, R606.6.3.1
Kitchen Height and area R312, R313 Sinks R326
Ventilation R325.1.2
Labeling Garage doors R609.4.1 Ladders
Ships ladders R318.7.13 Sleeping lofts R315.5.3 Landings (see also Stairways, Ramps and Doors) R318.3, R318.3.1, R318.3.2, R318.7.6, R318.8.2, R321, R324.4.7, R325.6, R325.7 Lateral Support R502.7, R606.6.4, R607.5.2 Lath
Exterior R703.7.1
Interior R702.2.3
Lavatories R326.1
Clearances R327 Liability R104.8 Light R325 Lighting Adjoining rooms R325.1.3 Bathrooms R325.2
CRC § 4-14 High relevance — show source text
Constructed in accordance with ASCE 32.
Erected on solid rock.
Footings shall not bear on frozen soil unless the frozen condition is permanent.
Exceptions:
- Protection of free-standing accessory structures with an area of 600 square feet (56 m [2] ) or less, of light-frame construction, with an eave height of 10 feet (3048 mm) or less shall not be required.
- Protection of free-standing accessory structures with an area of 400 square feet (37 m [2] ) or less, of other than lightframe construction, with an eave height of 10 feet (3048 mm) or less shall not be required.
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FOUNDATIONS
R403.1.5 Slope. The top surface of footings shall be level. The bottom surface of footings shall not have a slope exceeding 1 unit vertical in 10 units horizontal (10-percent slope). Footings shall be stepped where it is necessary to change the elevation of the top surface of the footings or where the slope of the bottom surface of the footings will exceed 1 unit vertical in 10 units horizontal (10percent slope).
R403.1.6 Foundation anchorage. Wood sill plates and wood walls supported directly on continuous foundations shall be anchored to the foundation in accordance with this section.
Cold-formed steel framing shall be anchored directly to the foundation or fastened to wood sill plates in accordance with Section R505.3.1 or R603.3.1, as applicable. Wood sill plates supporting cold-formed steel framing shall be anchored to the foundation in accordance with this section.
Wood sole plates at all exterior walls on monolithic slabs, wood sole plates of braced wall panels at building interiors on monolithic slabs and all wood sill plates shall be anchored to the foundation with minimum [1] / 2 -inch-diameter (12.7 mm) anchor bolts spaced not greater than 6 feet (1829 mm) on center or approved anchors or anchor straps spaced as required to provide equivalent anchorage to [1] / 2 -inch-diameter (12.7 mm) anchor bolts. Bolts shall extend not less than 7 inches (178 mm) into concrete or grouted cells of concrete masonry units. The bolts shall be located in the middle third of the width of the plate. A nut and washer shall be tightened on each anchor bolt. There shall be not fewer than two bolts per plate section with one bolt located not more than 12 inches (305 mm) or less than seven bolt diameters from each end of the plate section. Interior bearing wall sole plates on monolithic slab foundation that are not part of a braced wall panel shall be positively anchored with approved fasteners. Sill plates and sole plates shall be protected against decay and termites where required by Sections R304 and R305. Anchor bolts shall be permitted to be located while concrete is still plastic and before it has set. Where anchor bolts resist placement or the consolidation of concrete around anchor bolts is impeded, the concrete shall be vibrated to ensure full contact between the anchor bolts and concrete.
CRC § 2304.11.4.1 High relevance — show source text
2304.11.4.1 Cross-laminated timber roofs. Cross-laminated timber roofs shall be not less than 3 inches (76 mm) in thickness and shall be continuous from support to support and mechanically fastened to one another.
2304.11.4.2 Sawn, wood structural panel, or glued-laminated plank roofs. Sawn, wood structural panel, or glued-laminated plank roofs shall be one of the following:
- Sawn or glued laminated, splined or tongue-and-groove plank, not less than 2 inches (51 mm) nominal in thickness.
- 1 [1] / 8 -inch-thick (32 mm) wood structural panel (exterior glue).
- Planks not less than 3 inches (76 mm) nominal in width, set on edge close together and laid as required for floors.
2304.12 Protection against decay and termites. Wood shall be protected from decay and termites in accordance with the applicable provisions of Sections 2304.12.1 through 2304.12.4.
2304.12.1 Locations requiring waterborne preservatives or naturally durable wood. Wood used above ground in the locations specified in Sections 2304.12.1.1 through 2304.12.1.5 shall be naturally durable wood or preservative-treated wood using waterborne preservatives, in accordance with AWPA U1 for above-ground use.
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WOOD
2304.12.1.1 Joists, girders and subfloor. Wood joists or wood structural floors that are closer than 18 inches (457 mm) or wood girders that are closer than 12 inches (305 mm) to the exposed ground in crawl spaces or unexcavated areas located within the perimeter of the building foundation shall be of naturally durable or preservative-treated wood.
2304.12.1.1.1 [SPCB] There shall be a clearance of at least 18 inches (457 mm) between the underside of wood floor joists and the finished surface of the ground, and at least 12 inches (305 mm) between the underside of any other wood horizontal framing member and the finished surface of the ground. The ground underneath floor joists shall be leveled or smoothed off so as to maintain a reasonably even surface.
Exception: For purposes of structural pest control inspection, a minimum of 12 inches (305 mm) of clearance under-floor joists shall be considered adequate except that such clearance shall not be necessary where the subarea soil is of such a nature as to prevent excavation or where excavation would create a hazard from shifting soil or other causes.
2304.12.1.2 Wood supported by exterior foundation walls. Wood framing members, including wood sheathing, that are in contact with exterior foundation walls and are less than 8 inches (203 mm) from exposed earth shall be of naturally durable or preservative-treated wood.
Exception: [DSA-SS and OSHPD 1, 1R, 2, 4 & 5] At exterior walls where the earth is paved with an asphalt or concrete slab at least 18 inches (457 mm) wide and draining away from the building, the bottom of sills are permitted to be 6 inches (152 mm) above the top of such slab. Other equivalent means of termite and decay protection may be accepted by the enforcement agency.
CRC § 5.12 High relevance — show source text
R303.5.12 Sheathing. Foam plastic insulation used as sheathing shall comply with Section R303.3 and Section R303.4. Where the foam plastic sheathing is exposed to the attic space at a gable or kneewall, the provisions of Section R303.5.3 shall apply. Where foam plastic insulation is used as exterior wall sheathing on framed wall assemblies, it shall comply with Section R303.8.
R303.5.13 Floors. The thermal barrier specified in Section R303.4 is not required to be installed on the walking surface of a structural floor system that contains foam plastic insulation where the foam plastic is covered by not less than a nominal [1] / 2 -inch-thick (12.7 mm) wood structural panel or equivalent. The thermal barrier specified in Section R303.4 is required on the underside of the structural floor system that contains foam plastic insulation where the underside of the structural floor system is exposed to the interior of the building.
R303.6 Specific approval. Foam plastic not meeting the requirements of Sections R303.3 through R303.5 shall be specifically approved on the basis of an approved large-scale test reflecting the actual end-use configuration and performed on the finished foam plastic assembly in the maximum thickness intended for use. Assemblies tested shall include seams, joints and other typical details used in the installation of the assembly and shall be tested in the manner intended for use. The approved large-scale test shall comply with one of the following: NFPA 286 with the acceptance criteria of Section R302.9.4, FM 4880, UL 1040 or UL 1715.
R303.7 Termite damage. The use of foam plastics in areas of “very heavy” termite infestation probability shall be in accordance with Section R305.4.
R303.8 Wind resistance. Foam plastic insulation complying with ASTM C578 and ASTM C1289 and used as exterior wall sheathing on framed wall assemblies shall comply with ANSI/ABTG FS 100 for wind pressure resistance unless installed directly over or under a sheathing material that is separately capable of resisting the wind load or otherwise exempted from the scope of ANSI/ABTG FS 100.
SECTION R304—PROTECTION OF WOOD AND WOOD-BASED PRODUCTS AGAINST DECAY
R304.1 Location required. Protection of wood and wood-based products from decay shall be provided in the following locations by the use of naturally durable wood or wood that is preservative-treated in accordance with AWPA U1.
- In crawl spaces or unexcavated areas located within the periphery of the building foundation, wood joists or the bottom of a wood structural floor where closer than 18 inches (457 mm) to exposed ground, wood girders where closer than 12 inches (305 mm) to exposed ground, and wood columns where closer than 8 inches (204 mm) to exposed ground.
- Wood framing members, including columns, that rest directly on concrete or masonry exterior foundation walls and are less than 8 inches (203 mm) from the exposed ground.
- Sills and sleepers on a concrete or masonry slab that is in direct contact with the ground unless separated from such slab by an impervious moisture barrier.
- The ends of wood girders entering exterior masonry or concrete walls having clearances of less than [1] / 2 inch (12.7 mm) on tops, sides and ends.
2025 CALIFORNIA RESIDENTIAL CODE 3-33
CRC § 2304.12.2.4 High relevance — show source text
Exception: Sawn lumber in buildings located in a geographical region where experience has demonstrated that climatic conditions preclude the need to use durable materials where the structure is exposed to the weather.
2304.12.2.4 Supporting members for permeable floors and roofs. Wood structural members that support moisture-permeable floors or roofs that are exposed to the weather, such as concrete or masonry slabs, shall be of naturally durable or preservative-treated wood unless separated from such floors or roofs by an impervious moisture barrier. The impervious moisture barrier system protecting the structure supporting floors shall provide positive drainage of water that infiltrates the moisture-permeable floor topping.
2304.12.2.5 Ventilation beneath balcony or elevated walking surfaces. Enclosed framing in exterior balconies and elevated walking surfaces that have weather-exposed surfaces 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.
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WOOD
2304.12.2.6 Wood in contact with the ground or fresh water. Wood used in contact with exposed earth shall be naturally durable for both decay and termite resistance or preservative treated in accordance with AWPA U1 for soil or freshwater use.
Exception: Untreated wood is permitted where such wood is continuously and entirely below the ground-water level or submerged in fresh water.
2304.12.2.6.1 Posts or columns. Posts and columns that are supporting permanent structures and embedded in concrete that is exposed to the weather or in direct contact with the earth shall be of preservative-treated wood.
2304.12.2.7 Termite protection. In geographical areas where hazard of termite damage is known to be very heavy, wood floor framing in the locations specified in Section 2304.12.1.1 and exposed framing of exterior decks or balconies shall be of naturally durable species (termite resistant) or preservative treated in accordance with AWPA U1 for the species, product preservative and end use or provided with approved methods of termite protection.
2304.12.2.8 Wood used in retaining walls and cribs. Wood installed in retaining or crib walls shall be preservative treated in accordance with AWPA U1 for soil and freshwater use.
2304.12.3 Attic ventilation. For attic ventilation, see Section 1202.2.2.
2304.12.4 Under-floor ventilation (crawl space). For under-floor ventilation (crawl space), see Section 1202.4.
2304.12.8 Separate wood framing. [SPCB] Correct the conditions in frame and stucco walls and similar appurtenant construction so that the wood framing is separate from the main structure by a complete concrete or masonry plug with no voids that will allow infestations to enter the structure from the wall. If there is no plug, the foundation shall be 2 inches (51 mm) or more above the grade levels and at least as high as the adjoining slabs or 4-inch (102 mm) concrete barrier seat off installed.
Frequently asked questions
What counts as “preservative‑treated” wood?
Preservative‑treated wood is wood treated in accordance with AWPA standards for the intended use (above‑ground or soil contact). The lumber required by the CRC must bear an approved quality mark (see § R305.1.1).
If I use concrete piers, do columns still need treatment?
If wood columns rest on concrete piers or metal pedestals that project not less than 1 inch above the slab and are separated from the concrete pier by an impervious moisture barrier, treatment may not be required per § R304.1.9.
Can I rely on a metal termite shield alone?
No. Metal shields placed on top of an exterior foundation wall are acceptable only when used in combination with another approved method of protection — see § R305.3.
Do I have to retreat cuts in treated lumber on site?
Yes. Field‑cut ends, notches and drilled holes of pressure‑preservative‑treated wood must be retreated in the field in accordance with AWPA M4 as required by § R305.1.2.
What fasteners should I use with treated wood?
Fasteners in contact with preservative‑treated wood must be of hot‑dipped galvanized steel, stainless steel, silicon bronze or copper (or as manufacturer specifies) — see § R304.3.
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