CRC · California Residential Code
Wood floor framing
Wood floor framing in the CRC is covered primarily in Section R502 (with R503–R505 and R504 for sheathing, steel framing and on‑ground floors) and provides the span tables, bearing, lateral‑restraint and notching rules used to size and construct typical residential wood floors.
Last reviewed: July 6, 2026
Overview
This hub covers the CRC prescriptive rules and tables used to size and build raised wood floor systems: joists, girders, bearing details, rim/band joists, bridging/blocking, allowable spans and the attachment of subfloor sheathing (§ R501–R502). Chapter 5 provides the overall scope for floors and introduces Section R502—Wood Floor Framing (§ R502.1)—which governs lumber identification, engineered members and general framing requirements .
You’ll rely on the CRC’s allowable span tables and joist-sizing rules (see § R502.3 and Tables R502.3.1(1)/(2)), plus bearing and load-path requirements (§ R502.6–R502.7) and limits on cutting, drilling and notching (§ R502.8). Floor sheathing and fastening/attachment rules are in § R503, while pressure‑treated on‑ground floors and cold‑formed steel floor framing are handled in § R504 and § R505 respectively—these sections contain the prescriptive tables, figures and fastening schedules you’ll use on typical residential projects .
In this section
Code references
Grounded in the retrieved California Residential Code — click a citation to read the verbatim passage:
CRC § 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 § 2025 High relevance — show source text
The prescriptive provisions of this chapter provide requirements for constructing footings and walls for foundations of wood, masonry, concrete and precast concrete. In addition to a foundation’s ability to support the required design loads, this chapter addresses several other factors that can affect foundation performance. These include controlling surface water and subsurface drainage, requiring soil tests where conditions warrant and evaluating proximity to slopes and minimum depth requirements. The chapter also provides requirements to minimize adverse effects of moisture, decay and pests in basements and crawl spaces.
Chapter 5 Floors.
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 four different types: 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.
Chapter 6 Wall Construction.
Chapter 6 contains provisions that regulate the design and construction of walls. The wall construction covered in Chapter 6 consists of five different types: wood framed, cold-formed steel framed, masonry, concrete and structural insulated panel (SIP). The primary concern of this chapter is the structural integrity of wall construction and transfer of all imposed loads to the supporting structure. This chapter provides the requirements for the design and construction of wall systems that are capable of supporting the minimum design vertical loads (dead, live and snow loads) and lateral loads (wind or seismic loads). This chapter contains the prescriptive requirements for wall bracing and/or shear walls to resist the imposed lateral loads due to wind and seismic activity.
Chapter 6 also regulates exterior windows and doors installed in walls. This chapter contains criteria for the performance of exterior windows and doors and includes provisions for testing and labeling, garage doors, windborne debris protection and anchorage details.
Chapter 7 Wall Covering.
Chapter 7 contains provisions for the design and construction of interior and exterior wall coverings. This chapter establishes the various types of materials, materials standards and methods of application permitted for use as interior coverings, including interior plaster, gypsum board, ceramic tile, wood veneer paneling, hardboard paneling, wood shakes and wood shingles. Chapter 7 also contains requirements for the use of vapor retarders for moisture control in walls.
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Exterior wall coverings provide the weather-resistant exterior envelope that protects the building’s interior from the elements. Chapter 7 provides the requirements for wind resistance and water-resistive barrier for exterior wall coverings. This chapter prescribes the exterior wall coverings as well as the water-resistive barrier required beneath the exterior materials. Exterior wall coverings regulated by this section include aluminum, stone and masonry veneer, wood, hardboard, particleboard, wood structural panel siding, wood shakes and shingles, exterior plaster, steel, vinyl, fiber cement and exterior insulation finish systems.
Chapter 8 Roof-Ceiling Construction.
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 § 6.1 High relevance — show source text
The sill plate shall provide a minimum nominal bearing area of 48 square inches (30 865 mm [2] ).
R502.6.1 Floor systems. Joists framing from opposite sides over a bearing support shall lap not less than 3 inches (76 mm) and shall be nailed together with a minimum three 10d face nails. A wood or metal splice with strength equal to or greater than that provided by the nailed lap is permitted.
R502.6.2 Joist framing. Joists framing into the side of a wood girder shall be supported by approved framing anchors or on ledger strips not less than nominal 2 inches by 2 inches (51 mm by 51 mm).
R502.7 Lateral restraint at supports. Joists shall be supported laterally at the ends by full-depth solid blocking not less than 2 inches (51 mm) nominal in thickness; or by attachment to a full-depth header, band or rim joist, or to an adjoining stud or shall be otherwise provided with lateral support to prevent rotation.
Exceptions:
- Trusses, structural composite lumber, structural glued-laminated members and I-joists shall be supported laterally as required by the manufacturer’s recommendations.
- In Seismic Design Categories D 0, D 1 and D 2, lateral restraint shall be provided at each intermediate support.
R502.7.1 Bridging. Joists exceeding a nominal 2 inches by 12 inches (51 mm by 305 mm) shall be supported laterally by solid blocking, diagonal bridging (wood or metal), or a continuous 1-inch by 3-inch (25 mm by 76 mm) strip nailed across the bottom of joists perpendicular to joists at intervals not exceeding 8 feet (2438 mm).
Exception: Trusses, structural composite lumber, structural glued-laminated members and I-joists shall be supported laterally as required by the manufacturer’s recommendations.
R502.8 Cutting, drilling and notching. Structural floor members shall not be cut, bored or notched in excess of the limitations specified in this section. See Figure R502.8.
FIGURE R502.8—CUTTING, NOTCHING AND DRILLING
Col1 Col2 Col3 Col4 Col5 Col6 D/4 MAX. D/4 MAX. D/4 MAX. D/4 MAX. PIPE OR CONDUIT
D
D/3 MAX.
FLOOR JOIST— END CUTS
2 IN. MIN. FROM TOP AND BOTTOM OF JOIST
For SI: 1 inch = 25.4 mm.
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CRC § 25.4 High relevance — show source text
Applicable to all grades of sanded exterior-type plywood.|For SI: 1 inch = 25.4 mm, 1 pound per square foot = 0.0479 kPa.
a. Plywood continuous over two or more spans and face grain perpendicular to supports. Unsupported edges shall be tongue-and-groove or blocked except where nominal1/4-
inch-thick wood panel-type underlayment, fiber-cement underlayment or3/4-inch wood finish floor is used. Fiber-cement underlayment shall comply with ASTM C1288 or ISO
8336 Category C. Allowable uniform live load at maximum span based on deflection of1/360 of span is 100 psf.
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R503.2.2 Allowable spans. The maximum allowable span for wood structural panels used as subfloor or combination subfloor underlayment shall be as set forth in Table R503.2.1.1(1), or APA E30. The maximum span for sanded plywood combination subfloor underlayment shall be as set forth in Table R503.2.1.1(2).
R503.2.3 Installation. Wood structural panels used as subfloor or combination subfloor underlayment shall be attached to wood framing in accordance with Table R602.3(1) and shall be attached to cold-formed steel framing in accordance with Table R505.3.1(2).
R503.3 Particleboard.
R503.3.1 Identification and grade. Particleboard shall conform to ANSI A208.1 and shall be so identified by a grade mark or certificate of inspection issued by an approved agency. R503.3.2 Floor underlayment. Particleboard floor underlayment shall conform to Type PBU and shall be not less than [1] / 4 inch (6.4 mm) in thickness.
R503.3.3 Installation. Particleboard underlayment shall be installed in accordance with the recommendations of the manufacturer and attached to framing in accordance with Table R602.3(1).
SECTION R504—PRESSURE PRESERVATIVE-TREATED WOOD FLOORS (ON GROUND)
R504.1 General. Pressure preservative-treated wood basement floors and floors on ground shall be designed to withstand axial forces and bending moments resulting from lateral soil pressures at the base of the exterior walls and floor live and dead loads. Floor framing shall be designed to meet joist deflection requirements in accordance with Section R301.
R504.1.1 Unbalanced soil loads. Unless special provision is made to resist sliding caused by unbalanced lateral soil loads, wood basement floors shall be limited to applications where the differential depth of fill on opposite exterior foundation walls is 2 feet (610 mm) or less.
R504.1.2 Construction. Joists in wood basement floors shall bear tightly against the narrow face of studs in the foundation wall or directly against a band joist that bears on the studs. Plywood subfloor shall be continuous over lapped joists or over butt joints between in-line joists. Sufficient blocking shall be provided between joists to transfer lateral forces at the base of the end walls into the floor system.
CRC § 2.1 Medium relevance — show source text
R502.2.1 Framing at braced wall lines. A load path for lateral forces shall be provided between floor framing and braced wall panels located above or below a floor, as specified in Section R602.10.8.
R502.2.2 Blocking and subflooring. Blocking for fastening panel edges or fixtures shall be not less than utility grade lumber. Subflooring shall be not less than utility grade lumber, No. 4 common grade boards or wood structural panels as specified in Section R503.2. Fireblocking shall be of any grade lumber.
R502.3 Allowable joist spans. Spans for floor joists shall be in accordance with Tables R502.3.1(1) and R502.3.1(2). For other grades and species and for other loading conditions, refer to the AWC STJR.
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R502.3.1 Sleeping areas and attic joists. Table R502.3.1(1) shall be used to determine the maximum allowable span of floor joists that support sleeping areas and attics that are accessed by means of a fixed stairway in accordance with Section R318.7 provided that the design live load does not exceed 30 pounds per square foot (1.44 kPa) and the design dead load does not exceed 20 pounds per square foot (0.96 kPa). The allowable span of ceiling joists that support attics used for limited storage or no storage shall be determined in accordance with Section R802.5.
TABLE R502.3.1(1)—FLOOR JOIST SPANS FOR COMMON LUMBER SPECIES
(Residential sleeping areas, live load = 30 psf, L/Δ = 360)aCol2 Col3 Col4 Col5 Col6 Col7 Col8 Col9 Col10 Col11 ** JOIST SPACING**
(inches)** SPECIES AND GRADE** ** SPECIES AND GRADE** ** DEAD LOAD = 10 psf** ** DEAD LOAD = 10 psf** ** DEAD LOAD = 10 psf** ** DEAD LOAD = 10 psf** ** DEAD LOAD = 20 psf** ** DEAD LOAD = 20 psf** ** DEAD LOAD = 20 psf** ** DEAD LOAD = 20 psf** ** JOIST SPACING**
(inches)** SPECIES AND GRADE** ** SPECIES AND GRADE** ** 2 × 6** ** 2 × 8** ** 2 × 10** ** 2 × 12** ** 2 × 6** ** 2 × 8** ** 2 × 10** ** 2 × 12** ** JOIST SPACING**
(inches)** SPECIES AND GRADE** ** SPECIES AND GRADE** ** Maximum floor joist spans** ** Maximum floor joist spans** ** Maximum floor joist spans** ** Maximum floor joist spans** ** Maximum floor joist spans** ** Maximum floor joist spans** ** Maximum floor joist spans** ** Maximum floor joist spans** ** JOIST SPACING**
(inches)** SPECIES AND CRC § 5-9 Medium relevance — show source text
Linear interpolation shall be permitted for ground snow loads other than shown.|
R502.4 Joists under bearing partitions. Joists under parallel bearing partitions shall be of adequate size to support the load. Double joists, sized to adequately support the load, that are separated to permit the installation of piping or vents shall be full-depth solid blocked with lumber not less than 2 inches (51 mm) in nominal thickness spaced not more than 4 feet (1219 mm) on center. Bearing partitions perpendicular to joists shall not be offset from supporting girders, walls or partitions more than the joist depth unless such joists are of sufficient size to carry the additional load.
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R502.5 Allowable girder and header spans. The allowable spans of girders and headers fabricated of dimension lumber shall not exceed the values set forth in Tables R602.7(1), R602.7(2) and R602.7(3). R502.6 Bearing. The ends of each joist, beam or girder shall have not less than 1 [1] / 2 inches (38 mm) of bearing on wood or metal, have not less than 3 inches of bearing (76 mm) on masonry or concrete or be supported by approved joist hangers. Alternatively, the ends of joists shall be supported on a 1-inch by 4-inch (25 mm by 102 mm) ribbon strip and shall be nailed to the adjacent stud. The bearing on masonry or concrete shall be direct, or a sill plate of 2-inch-minimum (51 mm) nominal thickness shall be provided under the joist, beam or girder. The sill plate shall provide a minimum nominal bearing area of 48 square inches (30 865 mm [2] ).
R502.6.1 Floor systems. Joists framing from opposite sides over a bearing support shall lap not less than 3 inches (76 mm) and shall be nailed together with a minimum three 10d face nails. A wood or metal splice with strength equal to or greater than that provided by the nailed lap is permitted.
R502.6.2 Joist framing. Joists framing into the side of a wood girder shall be supported by approved framing anchors or on ledger strips not less than nominal 2 inches by 2 inches (51 mm by 51 mm).
R502.7 Lateral restraint at supports. Joists shall be supported laterally at the ends by full-depth solid blocking not less than 2 inches (51 mm) nominal in thickness; or by attachment to a full-depth header, band or rim joist, or to an adjoining stud or shall be otherwise provided with lateral support to prevent rotation.
Exceptions:
- Trusses, structural composite lumber, structural glued-laminated members and I-joists shall be supported laterally as required by the manufacturer’s recommendations.
- In Seismic Design Categories D 0, D 1 and D 2, lateral restraint shall be provided at each intermediate support.
R502.7.1 Bridging. Joists exceeding a nominal 2 inches by 12 inches (51 mm by 305 mm) shall be supported laterally by solid blocking, diagonal bridging (wood or metal), or a continuous 1-inch by 3-inch (25 mm by 76 mm) strip nailed across the bottom of joists perpendicular to joists at intervals not exceeding 8 feet (2438 mm).
CRC § 1.3 Medium relevance — show source text
R504.1.3 Uplift and buckling. Where required, resistance to uplift or restraint against buckling shall be provided by interior bearing walls or properly designed stub walls anchored in the supporting soil below.
R504.2 Site preparation. The area within the foundation walls shall have all vegetation, topsoil and foreign material removed, and any fill material that is added shall be free of vegetation and foreign material. The fill shall be compacted to ensure uniform support of the pressure preservative-treated wood floor sleepers. R504.2.1 Base. A minimum 4-inch-thick (102 mm) granular base of gravel having a maximum size of [3] / 4 inch (19.1 mm) or crushed stone having a maximum size of [1] / 2 inch (12.7 mm) shall be placed over the compacted earth.
R504.2.2 Moisture barrier. Polyethylene sheeting of minimum 6-mil (0.15 mm) thickness shall be placed over the granular base. Joints shall be lapped 6 inches (152 mm) and left unsealed. The polyethylene membrane shall be placed over the pressure preservative-treated wood sleepers and shall not extend beneath the footing plates of the exterior walls.
R504.3 Materials. Framing materials, including sleepers, joists, blocking and plywood subflooring, shall be pressure-preservative treated and dried after treatment in accordance with AWPA U1 (Commodity Specification A, Special Requirement 4.2), and shall bear the label of an accredited agency.
SECTION R505—COLD-FORMED STEEL FLOOR FRAMING
R505.1 Cold-formed steel floor framing. Elements shall be straight and free of any defects that would significantly affect structural performance. Cold-formed steel floor framing members shall be in accordance with the requirements of this section.
R505.1.1 Applicability limits. The provisions of this section shall control the construction of cold-formed steel floor framing for buildings not greater than 60 feet (18 288 mm) in length perpendicular to the joist span, not greater than 40 feet (12 192 mm) in width parallel to the joist span and less than or equal to three stories above grade plane. Cold-formed steel floor framing constructed in accordance with the provisions of this section shall be limited to sites where the ultimate design wind speed is less than 140 miles per hour (63 m/s), Exposure Category B or C, and the ground snow load is less than or equal to 70 pounds per square foot (3.35 kPa).
R505.1.1.1 Alternate applications. Cold-formed steel floor framing for buildings exceeding the applicability limits of Section R505.1.1 is permitted to be designed and constructed in accordance with AISI S230, subject to the limits therein.
R505.1.2 In-line framing. Where supported by cold-formed steel-framed walls in accordance with Section R603, cold-formed steel floor framing shall be constructed with floor joists located in-line with load-bearing studs located below the joists in accordance with the tolerances specified in AISI S240, Section B1.2.3.
CRC § 6-45 Medium relevance — show source text
END OF BRACED WALL LINE
FIRST BRACED
WALL PANEL
D*
10′ MAX
CONTINUOUSLY SHEATHED
BRACED WALL LINE
CONTINUOUSLY SHEATHED
BRACED WALL LINE
CONTINUOUSLY SHEATHED
BRACED WALL LINE
CONTINUOUSLY SHEATHED
BRACED WALL LINE
END CONDITION 2
END CONDITION 3
END CONDITION 5
END CONDITION 4
REQUIREMENTS
Return panel: 24″ for braced wall lines sheathed with
wood structural panels
32″ for braced wall lines sheathed with
structural fiberboard
24″ for braced wall lines sheathed with
wood structural panels
32″ for braced wall lines sheathed with
structural fiberboard
Distance D:
800 lbs capacity fastened to the edge of the
braced wall panel closest to the corner and
to the foundation or floor framing below
Hold-down
device:
10′ MAX
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WALL CONSTRUCTION
R602.10.8 Braced wall panel connections. Braced wall panels shall be connected to floor framing or foundations as follows:
- Where joists are perpendicular to a braced wall panel above or below, a rim joist, band joist or blocking shall be provided along the entire length of the braced wall panel in accordance with Figure R602.10.8(1). Fastening of top and bottom wall plates to framing, rim joist, band joist or blocking shall be in accordance with Table R602.3(1).
- Where joists are parallel to a braced wall panel above or below, a rim joist, end joist or other parallel framing member shall be provided directly above and below the braced wall panel in accordance with Figure R602.10.8(2). Where a parallel framing member cannot be located directly above and below the panel, full-depth blocking at 16-inch (406 mm) spacing shall be provided between the parallel framing members to each side of the braced wall panel in accordance with Figure R602.10.8(2). Fastening of blocking and wall plates shall be in accordance with Table R602.3(1) and Figure R602.10.8(2).
CRC § 6.1. Medium relevance — show source text
- The entire length of the braced wall panel does not occur over an opening in the wall below.
- Floor and roof opening. Conditions where an opening in a floor or roof exceeds the lesser of 12 feet (3658 mm) or 50 percent of the least floor or roof dimension.
- Floor level offset. Conditions where portions of a floor level are vertically offset.
Exceptions:
- Framing supported directly by continuous foundations at the perimeter of the building.
- For wood light-frame construction, floors shall be permitted to be vertically offset where the floor framing is lapped or tied together as required by Section R502.6.1.
- Perpendicular shear wall and wall bracing. Conditions where shear walls and braced wall lines do not occur in two perpendicular directions.
- Wall bracing in stories containing masonry or concrete construction. Conditions where stories above grade plane are partially or completely braced by wood wall framing in accordance with Section R602 or cold-formed steel wall framing in accordance with Section R603 include masonry or concrete construction. Where this irregularity applies, the entire story shall be designed in accordance with accepted engineering practice.
Exception: Fireplaces, chimneys and masonry veneer in accordance with this code. 8. Hillside light-frame construction. Conditions in which all of the following apply: 8.1. The grade slope exceeds 1 unit vertical in 5 units horizontal where averaged across the full length of any side of the building.
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BUILDING PLANNING
8.2. The tallest cripple wall clear height exceeds 7 feet (2134 mm), or where a post and beam system occurs at the building perimeter, the post and beam system tallest post clear height exceeds 7 feet (2134 mm). 8.3. Of the total plan area below the lowest framed floor, whether open or enclosed, less than 50 percent is living space having interior wall finishes conforming to Section R702.
Where Item 8 is applicable, design in accordance with accepted engineering practice shall be provided for the floor immediately above the cripple walls or post and beam system and all structural elements and connections from this diaphragm down to and including connections to the foundation and design of the foundation to transfer lateral loads from the framing above.
Exception: Light-frame construction in which the lowest framed floor is supported directly on concrete or masonry walls over the full length of all sides except the downhill side of the building need not be considered an irregular building under Item 8.
R301.2.2.7 Height limitations. Wood-framed buildings shall be limited to three stories above grade plane or the limits given in Table R602.10.3(3). Wood-framed buildings in Seismic Design Category D 2 exceeding two stories shall be designed for wind and seismic loads in accordance with accepted engineering practice. Cold-formed steel-framed buildings shall be limited to less than or equal to three stories above grade plane in accordance with AISI S230. Mezzanines as defined in Section R202 that comply with Section R314 shall not be considered as stories. Structural insulated panel buildings shall be limited to two stories above grade plane.
CRC § 6.1 Medium relevance — show source text
SPAN
USE HANGER IF HEADER
SPANS MORE THAN
6 FT.||||||| |||HEADER-DOUBLE IF
MORE THAN 4 FT. SPAN
USE HANGER IF HEADER
SPANS MORE THAN
6 FT.||||||| |||HEADER-DOUBLE IF
MORE THAN 4 FT. SPAN
USE HANGER IF HEADER
SPANS MORE THAN
6 FT.||||||| |||HEADER-DOUBLE IF
MORE THAN 4 FT. SPAN
USE HANGER IF HEADER
SPANS MORE THAN
6 FT.||||||| |||HEADER-DOUBLE IF
MORE THAN 4 FT. SPAN
USE HANGER IF HEADER
SPANS MORE THAN
6 FT.||||||| |||HEADER-DOUBLE IF
MORE THAN 4 FT. SPAN
USE HANGER IF HEADER
SPANS MORE THAN
6 FT.|||||PIER|PIER| |||||||||| |||||||||| |||||||||| |||||||||| ||LAP JOIST 3 IN. MIN. OR
SPLICE–SEE SECTION
R502.6.1|LAP JOIST 3 IN. MIN. OR
SPLICE–SEE SECTION
R502.6.1|LAP JOIST 3 IN. MIN. OR
SPLICE–SEE SECTION
R502.6.1|||||| |||||||||| ||||||||||JOISTS–SEE SECTION
R502.7.1
PROVISION FOR PIPES
AND VENTS
DOUBLE JOISTS UNDER BEARING
PARTITIONS. IF JOISTS ARE SEPARATED FOR PIPES, BLOCK
4 FT. ON-CENTER MAXIMUM
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
R502.2.1 Framing at braced wall lines. A load path for lateral forces shall be provided between floor framing and braced wall panels located above or below a floor, as specified in Section R602.10.8.
R502.2.2 Blocking and subflooring. Blocking for fastening panel edges or fixtures shall be not less than utility grade lumber. Subflooring shall be not less than utility grade lumber, No. 4 common grade boards or wood structural panels as specified in Section R503.2. Fireblocking shall be of any grade lumber.
R502.3 Allowable joist spans. Spans for floor joists shall be in accordance with Tables R502.3.1(1) and R502.3.1(2). For other grades and species and for other loading conditions, refer to the AWC STJR.
5-4 2025 CALIFORNIA RESIDENTIAL CODE
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
FLOORS
R502.3.1 Sleeping areas and attic joists. Table R502.3.1(1) shall be used to determine the maximum allowable span of floor joists that support sleeping areas and attics that are accessed by means of a fixed stairway in accordance with Section R318.7 provided that the design live load does not exceed 30 pounds per square foot (1.44 kPa) and the design dead load does not exceed 20 pounds per square foot (0.96 kPa). The allowable span of ceiling joists that support attics used for limited storage or no storage shall be determined in accordance with Section R802.5.
|TABLE R502.3.
CRC § 4-8 Medium relevance — show source text
Joist to sill, top plate, or girder|4-8d box (21/2″ × 0.113″); or
3-8d common (21/2″ × 0.131″); or floor
3-10d box (3″ × 0.128″); or
3-3″ × 0.131″ nails; or
3-3″ 14 gage staples,7/16″ crown|Toenail| |22. Rim joist, band joist, or blocking to top plate, sill or other framing
below|8d box (21/2″ × 0.113″)|4_"_ o.c., toenail| |22. Rim joist, band joist, or blocking to top plate, sill or other framing
below|8d common (21/2″ × 0.131″); or
10d box (3″ × 0.128″); or
3″ × 0.131″ nails; or
3″ 14 gage staples,7/16″ crown|6″ o.c., toenail| |23. 1″ × 6″ subfloor or less to each joist|3-8d box (21/2″ × 0.113″); or
2-8d common (21/2″ × 0.131″); or
3-10d box (3″ × 0.128″); or
2-13/4″ 16 gage staples, 1″ crown|Face nail| |24. 2 subfloor to joist or girder|3-16d box (31/2″ × 0.135″); or
2-16d common (31/2″ × 0.162″)|Blind and face nail| |25. 2″ planks (plank & beam – floor & roof)|3-16d box (31/2″ × 0.135″); or
2-16d common (31/2″ × 0.162″)|Each bearing, face nail|2025 CALIFORNIA BUILDING CODE 23-19
on Jul 18, 2025 11:14 AM (CDT) THEREUNDER.
WOOD
TABLE 2304.10.2—FASTENING SCHEDULE—continued Col2 Col3 Col4 DESCRIPTION OF BUILDING ELEMENTS NUMBER AND TYPE OF FASTENERg SPACING AND LOCATION SPACING AND LOCATION 26. Built-up girders and beams, 2″ lumber layers 20d common (4″ × 0.192″) 32″ o.c., face nail at top and
bottom staggered on oppo-
site sides32″ o.c., face nail at top and
bottom staggered on oppo-
site sides26. Built-up girders and beams, 2″ lumber layers 10d box (3″ × 0.128″); or
3″ × 0.131″ nails; or
3″ 14 gage staples,7/16″ crown24″ o.c. face nail at top and
bottom staggered on oppo-
site sides24″ o.c. face nail at top and
bottom staggered on oppo-
site sides26.
Frequently asked questions
Where do I find the allowable joist spans for common lumber?
The allowable spans are in § R502.3 and the associated Tables R502.3.1(1) and R502.3.1(2), which give maximum spans by joist size, spacing, species/grade and design loads .
What section limits cutting, drilling or notching of floor joists?
Limits and illustrations for cutting, drilling and notching of structural floor members are given in § R502.8 (see Figure R502.8 for typical conditions) .
Are floors on the ground covered in the same section as raised floors?
No—pressure‑preservative‑treated wood floors on ground are addressed separately in § R504, which includes material, site preparation and construction requirements specific to on‑ground applications .
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