CRC · California Residential Code
Floors
Chapter 5 of the CRC (§R501–§R507) provides the prescriptive requirements and tables for wood, steel and concrete floors, exterior decks, and under‑floor moisture control.
Last reviewed: July 6, 2026
Overview
Chapter 5 of the California Residential Code (CRC) governs the design and construction of floor systems for one- and two-family dwellings and townhouses, setting minimum load, framing and detailing requirements so floors safely carry and transfer loads to the supporting structure (§R501–§R507) .
The chapter is largely prescriptive: wood floor framing and allowable-span tables are in §R502 and §R503, cold‑formed steel framing in §R505, on‑ground treated-wood and concrete slab requirements in §R504 and §R506, and exterior deck provisions in §R507 . Under-floor/crawlspace moisture control and ventilation are addressed in Chapter 4 and §R408 and include both vented and unvented crawl space options and vapor‑retarder details .
In this section
Code references
Grounded in the retrieved California Residential Code — click a citation to read the verbatim passage:
CRC § 4-6 High relevance — show source text
R403 Footings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6
R404 Foundation and Retaining Walls . . . . . . . . . . . . . . . . 4-24
R405 Foundation Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . 4-42
R406 Foundation Waterproofing and Dampproofing . . . 4-43
R407 Columns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-44
R408 Under-Floor Space . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-44
CHAPTER 5 FLOORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
R501 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
R502 Wood Floor Framing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
R503 Floor Sheathing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12
R504 Pressure Preservative-Treated Wood
Floors (On Ground) . . . . . . . . . . . . . . . . . . . . . . . . . . 5-14
R505 Cold-Formed Steel Floor Framing . . . . . . . . . . . . . . . 5-14
R506 Concrete Floors (On Ground) . . . . . . . . . . . . . . . . . . . 5-26
R507 Exterior Decks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26
CHAPTER 6 WALL CONSTRUCTION. . . . . . . . . . . . . . . . . . . 6-3
R601 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
R602 Wood Wall Framing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
R603 Cold-Formed Steel Wall Framing. . . . . . . . . . . . . . . . 6-53
R604 Wood Structural Panels . . . . . . . . . . . . . . . . . . . . . . . . 6-93
R605 Particleboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-93
R606 General Masonry Construction. . . . . . . . . . . . . . . . . . 6-93
CRC § 25.4 High relevance — show source text
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
(TYP.)
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FLOORS
SECTION R506—CONCRETE FLOORS (ON GROUND)
R506.1 General. Concrete slab-on-ground floors shall be designed and constructed in accordance with the provisions of this section or ACI 332. Such floors shall be not less than 3 [1] / 2 inches (89 mm) thick (for expansive soils, see Section R403.1.8). The specified compressive strength of concrete shall be as set forth in Section R402.2.
R506.2 Post-tensioned slab-on-ground floors. Post-tensioned concrete slabs-on-ground floors placed on expansive or stable soils shall be designed in accordance with PTI DC10.5.
R506.3 Site preparation. The area within the foundation walls shall have all vegetation, topsoil and foreign material removed.
R506.3.1 Fill. Fill material shall be free of vegetation and foreign material. The fill shall be compacted to ensure uniform support of the slab, and except where approved, the fill depths shall not exceed 24 inches (610 mm) for clean sand or gravel and 8 inches (203 mm) for earth.
R506.3.2 Base. A 4-inch-thick (102 mm) base course consisting of clean graded sand, gravel, crushed stone, crushed concrete or crushed blast-furnace slag passing a 2-inch (51 mm) sieve shall be placed on the prepared subgrade where the slab is below grade.
Exception: A base course is not required where the concrete slab is installed on well-drained or sand-gravel mixture soils classified as Group I according to the United Soil Classification System in accordance with Table R401.4.1(2).
R506.3.3 Vapor retarder. A minimum 6 mil (0.006 inch; 152 μ m) polyethylene or approved vapor retarder with joints lapped not less than 6 inches (152 mm) shall be placed between the concrete floor slab and the base course or the prepared subgrade where a base course does not exist.
Exception: The vapor retarder is not required for the following:
- Garages, utility buildings and other unheated accessory structures.
- For unheated storage rooms having an area of less than 70 square feet (6.5 m [2] ) and carports.
- Driveways, walks, patios and other flatwork not likely to be enclosed and heated at a later date.
- Where approved by the building official, based on local site conditions.
R506.3.3.1 Capillary break. When a vapor retarder is required, a capillary break shall be installed in accordance with the Califor- nia Green Building Standards Code, Chapter 4, Division 4.5.
R506.3.4 Reinforcement support. Where provided in slabs-on-ground, reinforcement shall be supported to remain in place from the center to upper one-third of the slab for the duration of the concrete placement.
SECTION R507—EXTERIOR DECKS
CRC § 0.0254 High relevance — show source text
RIM TRACK
WEB STIFFENER
SHEATHING
TRACK
JOIST
LOAD-BEARING STUD
For SI: 1 mil = 0.0254 mm, 1 inch = 25.4 mm.
FIGURE R505.3.1(2)—FLOOR-TO-WOOD-SILL CONNECTION
SHEATHING
RIM TRACK
MIN. 33 MIL THICK
SILL SEALER AS REQUIRED
For SI: 1 mil = 0.0254 mm, 1 inch = 25.4 mm.
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FLOORS
FIGURE R505.3.1(3)—FLOOR-TO-FOUNDATION CONNECTION
WEB STIFFENER
RIM TRACK (MIN. 33 MIL THICK)
SILL SEALER AS REQUIRED
For SI: 1 mil = 0.0254 mm, 1 inch = 25.4 mm.
FOUNDATION
FIGURE R505.3.1(4)—CANTILEVERED FLOOR-TO-FOUNDATION CONNECTION
SHEATHING
For SI: 1 mil = 0.0254 mm.
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FIGURE R505.3.1(5)—CANTILEVERED FLOOR-TO-WOOD-SILL CONNECTION
BLOCKING EVERY OTHER JOIST
CONNECTION OF BLOCKING
NO. 8 SCREW AT EACH FLANGE (TOP AND BOTTOM)
For SI: 1 mil = 0.0254 mm, 1 inch = 25.4 mm.
FIGURE R505.3.1(6)—CANTILEVERED FLOOR TO EXTERIOR LOAD-BEARING WALL CONNECTION
BLOCKING EVERY OTHER JOIST
WEB STIFFENER
RIM TRACK (MIN. 33 MIL THICK)
NO. 8 SCREWS THROUGH FLANGE, CLIP ANGLE OR BENT STIFFENER
CONNECTION OF BLOCKING
TO JOIST THROUGH EACH
LEG OF WEB STIFFENER OR
CLIP ANGLE WITH 2 NO. 8
SHEATHING
JOIST
TOP TRACK
LOAD-BEARING STUD
For SI: 1 mil = 0.0254 mm.
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FIGURE R505.3.1(7)—CONTINUOUS SPAN JOIST SUPPORTED ON INTERIOR LOAD-BEARING WALL
CONNECTION OF BLOCKING
JOIST
For SI: 1 mil = 0.0254 mm, 1 inch = 25.4 mm.
SHEATHING
EACH FLANGE
FIGURE R505.3.1(8)—LAPPED JOISTS SUPPORTED ON INTERIOR LOAD-BEARING WALL
TRACK
For SI: 1 inch = 25.4 mm.
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FIGURE R505.3.1(9)—BEARING STIFFENERS FOR END JOISTS
CRC § 5-14 High relevance — show source text
Floors (On Ground) . . . . . . . . . . . . . . . . . . . . . . . . . . 5-14
R505 Cold-Formed Steel Floor Framing . . . . . . . . . . . . . . . 5-14
R506 Concrete Floors (On Ground) . . . . . . . . . . . . . . . . . . . 5-26
R507 Exterior Decks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-26
CHAPTER 6 WALL CONSTRUCTION. . . . . . . . . . . . . . . . . . . 6-3
R601 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
R602 Wood Wall Framing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-3
R603 Cold-Formed Steel Wall Framing. . . . . . . . . . . . . . . . 6-53
R604 Wood Structural Panels . . . . . . . . . . . . . . . . . . . . . . . . 6-93
R605 Particleboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-93
R606 General Masonry Construction. . . . . . . . . . . . . . . . . . 6-93
R607 Glass Unit Masonry . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-106
R608 Exterior Concrete Wall Construction. . . . . . . . . . . . 6-107
R609 Exterior Windows and Doors. . . . . . . . . . . . . . . . . . . 6-172
R610 Structural Insulated Panel Wall Construction . . . 6-175
CHAPTER 7 WALL COVERING. . . . . . . . . . . . . . . . . . . . . . . . 7-3
R701 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3
R702 Interior Covering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-3
R703 Exterior Wall Covering . . . . . . . . . . . . . . . . . . . . . . . . . 7-10
R704 Exterior Soffits and Fascias. . . . . . . . . . . . . . . . . . . . . 7-32
R705 BIPV Systems for Exterior Wall Coverings and Fenestration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-35
CHAPTER 8 ROOF-CEILING CONSTRUCTION. . . . . . . . . . . 8-3
CRC § 2-2 High relevance — show source text
ceiling and
two center-bearing
floors|2-2 × 10|6-0|2|4-9|2|4-0|2|5-8|2|4-6|2|3-10|3|5-5|2|4-3|2|3-8|3| |Roof, ceiling and
two center-bearing
floors|2-2 × 12|7-0|2|5-7|2|4-9|3|6-8|2|5-4|3|4-6|3|6-4|2|5-0|3|4-3|3| |Roof, ceiling and
two center-bearing
floors|3-2 × 8|6-4|1|5-0|2|4-3|2|6-0|1|4-9|2|4-1|2|5-8|2|4-6|2|3-10|2| |Roof, ceiling and
two center-bearing
floors|3-2 × 10|7-6|2|5-11|2|5-1|2|7-1|2|5-8|2|4-10|2|6-9|2|5-4|2|4-7|2| |Roof, ceiling and
two center-bearing
floors|3-2 × 12|8-10|2|7-0|2|5-11|2|8-5|2|6-8|2|5-8|3|8-0|2|6-4|2|5-4|3| |Roof, ceiling and
two center-bearing
floors|4-2 × 8|7-3|1|5-9|1|4-11|2|6-11|1|5-6|2|4-8|2|6-7|1|5-2|2|4-5|2| |Roof, ceiling and
two center-bearing
floors|4-2 × 10|8-8|1|6-10|2|5-10|2|8-3|2|6-6|2|5-7|2|7-10|2|6-2|2|5-3|2| |Roof, ceiling and
two center-bearing
floors|4-2 × 12|10-2|2|8-1|2|6-10|2|9-8|2|7-8|2|6-7|2|9-2|2|7-3|2|6-2|2|6-18 2025 CALIFORNIA RESIDENTIAL CODE
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WALL CONSTRUCTION
|TABLE R602.7(1)—GIRDER SPANSa AND HEADER SPANSa FOR EXTERIOR BEARING WALLS
(Maximum spans for Douglas fir-larch, hem-fir, Southern pine and spruce-pine-firb and required number of jackCRC § 5-1 High relevance — show source text
The state agency does not adopt sections identified with the following symbol: †
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5 FLOORS
User notes:
About this chapter: Chapter 5 provides the requirements for the design and construction of floor systems that will be capable of supporting minimum required design loads. This chapter covers wood floor framing, wood floors on the ground, cold-formed steel floor framing and concrete slabs on the ground. Allowable span tables are provided that greatly simplify the determination of joist, girder and sheathing sizes for raised floor systems of wood framing and cold-formed steel framing. This chapter also contains prescriptive requirements for wood-framed exterior decks and their attachment to the main building.
SECTION R501—GENERAL
R501.1 Application. The provisions of this chapter shall control the design and construction of the floors for buildings, including the floors of attic spaces used to house mechanical or plumbing fixtures and equipment.
R501.2 Requirements. Floor construction shall be capable of accommodating all loads in accordance with Section R301 and of transmitting the resulting loads to the supporting structural elements.
SECTION R502—WOOD FLOOR FRAMING
R502.1 General. Wood and wood-based products used for load-supporting purposes shall conform to the applicable provisions of this section.
R502.1.1 Sawn lumber. Sawn lumber shall be identified by a grade mark of an accredited lumber grading or inspection agency and have design values certified by an accreditation body that complies with DOC PS 20. In lieu of a grade mark, a certificate of inspection issued by a lumber grading or inspection agency meeting the requirements of this section shall be accepted.
Note: See Section R301.1.1.1 for limited-density owner- built rural dwellings.
R502.1.1.1 Preservative-treated lumber. Preservative treated dimension lumber shall be identified as required by Section R304.2.
R502.1.1.2 End-jointed lumber. Approved end-jointed lumber identified by a grade mark conforming to Section R502.1.1 shall be permitted to be used interchangeably with solid-sawn members of the same species and grade. End-jointed lumber used in an assembly required elsewhere in this code to have a fire-resistance rating shall have the designation “Heat-Resistant Adhesive” or “HRA” included in its grade mark.
R502.1.2 Prefabricated wood I-joists. Structural capacities and design provisions for prefabricated wood I-joists shall be established and monitored in accordance with ASTM D5055.
R502.1.3 Structural glued-laminated timbers. Glued-laminated timbers shall be manufactured and identified as required in ANSI A190.1, ANSI 117 and ASTM D3737.
R502.1.4 Structural log members. Structural log members shall comply with the provisions of ICC 400.
R502.1.5 Structural composite lumber. Structural capacities for structural composite lumber shall be established and monitored in accordance with ASTM D5456.
R502.1.6 Cross-laminated timber. Cross-laminated timber shall be manufactured and identified as required by ANSI/APA PRG 320.
CRC § 5-14 High relevance — show source text
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R505.2 Structural framing. Load-bearing cold-formed steel floor framing members shall be in accordance with this section.
R505.2.1 Material. Load-bearing cold-formed steel framing members shall be cold formed to shape from structural quality sheet steel complying with the requirements of AISI S240, Section A3.
R505.2.2 Corrosion protection. Load-bearing cold-formed steel framing shall have a metallic coating complying with AISI S240, Section A4.
R505.2.3 Dimension, thickness and material grade. Load-bearing cold-formed steel floor framing members shall comply with AISI S230, Section A4.3 and material grade requirements as specified in AISI S230, Section A4.4.
R505.2.4 Identification. Load-bearing cold-formed steel framing members shall meet the product identification requirements of AISI S240, Section A5.5.
R505.2.5 Fastening. Screws for steel-to-steel connections shall be installed with a minimum edge distance and center-to-center spacing of [1] / 2 inch (12.7 mm), shall be self-drilling tapping, and shall conform to ASTM C1513. Floor sheathing shall be attached to cold-formed steel joists with minimum No. 8 self-drilling tapping screws that conform to ASTM C1513. Screws attaching floor sheathing to cold-formed steel joists shall have a minimum head diameter of 0.292 inch (7.4 mm) with countersunk heads and shall be installed with a minimum edge distance of [3] / 8 inch (9.5 mm). Gypsum board ceilings shall be attached to cold-formed steel joists with minimum No. 6 screws conforming to ASTM C954 or ASTM C1513 with a bugle-head style and shall be installed in accordance with Section R702. For all connections, screws shall extend through the steel not fewer than three exposed threads. Fasteners shall have a rust-inhibitive coating suitable for the installation in which they are being used, or be manufactured from material not susceptible to corrosion.
R505.2.6 Web holes, web hole reinforcing and web hole patching. Web holes in floor framing members shall comply with the conditions as prescribed in AISI S230, Section A4.5. Web holes not in compliance with the conditions as prescribed in AISI S230, Section A4.5 shall be reinforced in accordance with the provisions of AISI S230, Section A4.6 or patched in accordance with the provisions of AISI S230, Section A4.7.
R505.3 Floor construction. Cold-formed steel floors shall be constructed in accordance with this section.
R505.3.1 Floor-to-foundation or load-bearing wall connections. Cold-formed steel-framed floors shall be anchored to foundations, wood sills or load-bearing walls in accordance with Table R505.3.1(1) and Figure R505.3.1(1), R505.3.1(2), R505.3.1(3), R505.3.1(4), R505.3.1(5) or R505.3.1(6). Anchor bolts shall be located not more than 12 inches (305 mm) from corners or the termination of bottom tracks.
CRC § 3-82 Medium relevance — show source text
R336 Large Family Day-Care Homes . . . . . . . . . . . . . . . . . . . 3-82
R337 Materials and Construction Methods for Exterior
Wildfire Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-83
R338 Electric Vehicle . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-83
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CONTENTS
R339 Reserved . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-84
R340 Pollutant Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-84
CHAPTER 4 FOUNDATIONS . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
R401 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-3
R402 Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-5
R403 Footings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-6
R404 Foundation and Retaining Walls . . . . . . . . . . . . . . . . 4-24
R405 Foundation Drainage . . . . . . . . . . . . . . . . . . . . . . . . . . 4-42
R406 Foundation Waterproofing and Dampproofing . . . 4-43
R407 Columns. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-44
R408 Under-Floor Space . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-44
CHAPTER 5 FLOORS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
R501 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
R502 Wood Floor Framing . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3
R503 Floor Sheathing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12
R504 Pressure Preservative-Treated Wood
CRC § 1.6 Medium relevance — show source text
Foam plastics R302.8 Insulation R302.10, R302.14 Penetrations R302.4
Townhouse separation R302.2 Two-family dwellings R302.3 Under-stair protection R302.7 Wall and ceiling finishes R302.9 Fire-Separation Distance Exterior walls and wall projections R302.1 Ground-mounted photovoltaic systems R329.7, R329.8 Fixtures
Clearance R327.1
Flood protection R306.1.6 Plumbing fixture, general R326, R327 Flame Spread Index R302.10, R302.9 Flashing R703.4, R703.8.5, R903.2, R905 Flood Protection Plan Areas protected by the facilities of Central Valley Appendix CK Flood-Resistant Construction
General and structural R301.2.4, R306 Floors
Bathtub and shower R327.2 Concrete (on ground) R506 Loads R301, R501.2 Steel framing R505 Treated wood (on ground) R504
Wood framing R502 Flue
Area R1003.14, R1003.15 Lining R1003.11, R1003.12 Multiple R1003.13 Foam Plastics R303 Footings R403 Foundations Chapter 4 Cripple walls R602.10.9, R602.11.2, R602.9
Frost protection R403.1.4.1 Inspection R109.1.1 Walls R404
Frame
Inspection R109.1.4 Frost Protection R507.3, R507.3.3, R1001.2 Fuel Cell Power System, Stationary R322 Fuel-Burning Appliances (see Appliances)
Garbage Disposal (see Food-Waste Disposers) Garages R317, R330.8.1 Electric vehicle charging infrastructure R317.6 Protection of Energy Storage Systems R330.8
Generators R331
Girders R502.5 Glazing Aggregate area R325.1 Greenhouses R324.6.6 Protection of openings R301.2.1.2 Safety glazing at hazardous locations R324
Site-built R324.5 Skylights and sloped glazing R324.6 Grade
Of lumber R502.1.1, R602.1.1, R802.1.1 Grade Plane R101.2, R301.2.2.7, R316.3 Ground Floors (on ground) R504, R506 Guards or Guardrail R321, R324.4.4 Exterior R507.10 Guestroom (see Lodging House) Gypsum Board and Gypsum Panel Products R702.3
Hallways R318.6 Hand Shower (see Shower) Handrails R318.7.8, R318.8.3, R320, R324.4.4 Alternating tread devices R318.7.12.2 Ship’s ladders R318.7.13.2 Hazardous Location R324
Headers
SIP R610.8
Steel R603.6
Wood R602.7
CRC § 2.3.1 Medium relevance — show source text
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APPENDIX CK-8 2025 CALIFORNIA RESIDENTIAL CODE
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APPENDIX NA-2 2025 CALIFORNIA RESIDENTIAL CODE
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Concrete Capillary break R506.2.3.1 Compressive strength R402.2 Floors (on ground) R506 Tile (roof) R905.3 Weathering Figure R301.2(1), R402.2 Construction
3D-printed Appendix BM Cavity wall masonry R608 Cob Appendix BK Extended plate walls Appendix BN Flood-resistant R306
Floors Chapter 5 Footings R403 Foundation material R402
Foundation walls R404
Foundations Chapter 4 Hemp-lime Appendix BL Masonry R606, R607, R608, R610 Pollutant control R340 Roofs Chapter 8 Steel framing R505, R603, R804 Strawbale Appendix BJ Straw-clay Appendix BI Walls Chapter 6 Waste R334.1 Wood framing R502, R602, R802 Construction Documents R106, R306.3.9
Court Emergency escape and rescue openings R319.1, R319.2.4 Means of egress R318.1 Natural light R325.1.1 Covering Exterior R703
Interior R702 Roof Chapter 9 Wall Chapter 7 Crawl Space R408
Access R408.4
Damper Fireplace R1001.7.1 Dampproofing R406 Day Care Appendix BD Defined R202 Large family day-care homes R336 Dead Loads R301.4
Decay Protection against R304 Deck
Attachment R318.5 Supported by exterior wall R507 Wood/plastic composite boards R507.2.2
Definitions Building R202 Mechanical system R202 Plumbing R202 Design Criteria R301 Alternative provisions R301.1.1 Application R301.1 Climatic and geographic R301.2 Dead load R301.4
Deflection R301.6 Engineered design R301.1.3
Accessibility R322 Accessory Dwelling Unit R202 Authority to Enforce Automatic Fire Sprinkler Systems 1.8.9.1, R313.2 Accessory Structure Elevations R306.3.2
Energy R330.5 Exterior walls R302.1
Scope R101.2 Addition (see also Existing Buildings) Carbon monoxide alarms R311.2.2 Change of occupancy R110.1 Construction R302.2.3
CRC § 3.8 Medium relevance — show source text
Each header joist shall be connected to trimmer joists with four 2-inch by 2-inch (51-mm by 51-mm) clip angles. Each clip angle shall be fastened to both the header and trimmer joists with four No. 8 screws, evenly spaced, through each leg of the clip angle. The clip angles shall have a thickness not less than that of the floor joist. Each track section for a built-up header or trimmer joist shall extend the full length of the joist (continuous).
FIGURE R505.3.8(1)—COLD-FORMED STEEL FLOOR CONSTRUCTION—6-FOOT FLOOR OPENING
JOIST
CLIP ANGLE
For SI: 1 foot = 304.8 mm.
For SI: 1 foot = 304.8 mm.
JOIST
FIGURE R505.3.8(2)—COLD-FORMED STEEL FLOOR CONSTRUCTION—8-FOOT FLOOR OPENING
JOIST
CLIP ANGLE
JOIST
5-24 2025 CALIFORNIA RESIDENTIAL CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
FLOORS
WITH 4 NO. 8 SCREWS THROUGH EACH LEG, BOTH SIDES OF CONNECTION
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
MINIMUM 2 IN. × 2 IN. CLIP ANGLE
WITH 4 NO. 8 SCREWS THROUGH EACH LEG, BOTH SIDES OF CONNECTION
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
(TYP.)
2025 CALIFORNIA RESIDENTIAL CODE 5-25
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
FLOORS
SECTION R506—CONCRETE FLOORS (ON GROUND)
R506.1 General. Concrete slab-on-ground floors shall be designed and constructed in accordance with the provisions of this section or ACI 332. Such floors shall be not less than 3 [1] / 2 inches (89 mm) thick (for expansive soils, see Section R403.1.8). The specified compressive strength of concrete shall be as set forth in Section R402.2.
R506.2 Post-tensioned slab-on-ground floors. Post-tensioned concrete slabs-on-ground floors placed on expansive or stable soils shall be designed in accordance with PTI DC10.5.
R506.3 Site preparation. The area within the foundation walls shall have all vegetation, topsoil and foreign material removed.
R506.3.1 Fill. Fill material shall be free of vegetation and foreign material. The fill shall be compacted to ensure uniform support of the slab, and except where approved, the fill depths shall not exceed 24 inches (610 mm) for clean sand or gravel and 8 inches (203 mm) for earth.
R506.3.2 Base. A 4-inch-thick (102 mm) base course consisting of clean graded sand, gravel, crushed stone, crushed concrete or crushed blast-furnace slag passing a 2-inch (51 mm) sieve shall be placed on the prepared subgrade where the slab is below grade.
CRC § 916-574 Medium relevance — show source text
Note: Contact information for the California Department of Water Resources and the Department’s Directory of Flood Officials, which includes levee and reclamation district boundary maps, is available on-line at the following website: www.water.ca.gov/ BuildingCodes. The Department of Water Resources Building Code Project Engineer can be contacted at 916-574-1451. The Central Valley Flood Control Board Chief Engineer can be contacted at 916-574-0609. The California Emergency Management Agency Inland Region Program Manager can be contacted at 916-845-8488.
CK109.2 Appeals. When a request for an alternate means of protection has been denied by the building official, the applicant may file a written appeal with the board of appeals. In considering such appeal, the board of appeals may provide additional information to, and request additional written statements from the Central Valley Flood Protection Board, the California Department of Water Resources and the California Emergency Management Agency. If such additional written statements are provided, the board of appeals shall consider those statements.
2025 CALIFORNIA RESIDENTIAL CODE APPENDIX CK-5
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
APPENDIX CK — AREAS PROTECTED BY THE FACILITIES OF THE CENTRAL VALLEY FLOOD PROTECTION PLAN
APPENDIX CK-6 2025 CALIFORNIA RESIDENTIAL CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
APPENDIX CK — AREAS PROTECTED BY THE FACILITIES OF THE CENTRAL VALLEY FLOOD PROTECTION PLAN
2025 CALIFORNIA RESIDENTIAL CODE APPENDIX CK-7
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
APPENDIX CK-8 2025 CALIFORNIA RESIDENTIAL CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
2025 CALIFORNIA RESIDENTIAL CODE APPENDIX NA-1
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
APPENDIX NA-2 2025 CALIFORNIA RESIDENTIAL CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
Concrete Capillary break R506.2.3.1 Compressive strength R402.2 Floors (on ground) R506 Tile (roof) R905.3 Weathering Figure R301.2(1), R402.2 Construction
3D-printed Appendix BM Cavity wall masonry R608 Cob Appendix BK Extended plate walls Appendix BN Flood-resistant R306
Floors Chapter 5 Footings R403 Foundation material R402
Foundation walls R404
Foundations Chapter 4 Hemp-lime Appendix BL Masonry R606, R607, R608, R610 Pollutant control R340 Roofs Chapter 8 Steel framing R505, R603, R804 Strawbale Appendix BJ Straw-clay Appendix BI Walls Chapter 6 Waste R334.1 Wood framing R502, R602, R802 Construction Documents R106, R306.3.9
Frequently asked questions
What does Chapter 5 require for slab‑on‑ground construction?
Slab‑on‑ground floors must meet the R506 provisions (or ACI 332), including minimum thickness, site prep, base, reinforcement support and a minimum 6‑mil vapor retarder where required; exceptions are listed in §R506.3.3 .
Where are the prescriptive tables for wood joists and sheathing?
Prescriptive allowable‑span and fastening tables for wood floor joists and floor sheathing are provided in §R502 and §R503 of Chapter 5, which simplify joist, girder and sheathing sizing for typical raised floor systems .
How does the CRC treat crawlspace ventilation and unvented crawlspaces?
Under‑floor ventilation requirements and minimum net opening areas are given in §R408; unvented crawlspaces require a continuous Class I vapor retarder and specified mechanical or conditioned‑air strategies per §R408.3 .
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