CBC · California Building Code
What are the attic/rafter ventilation and cricket (saddle) requirements around penetrations?
The CBC requires attic/rafter ventilation per § 1202.2 (normally 1/150 of attic area) as referenced in § 1503.4, and requires a cricket/saddle on the ridge side of any roof penetration wider than 30 inches with sheet‑metal or matching covering under § 1503.5; the CBC points to § 1202.2 for vent sizing and allows specific exceptions (unvented attics, certain skylights).
Last reviewed: July 5, 2026
What the code requires — 2–4 sentences
The California Building Code requires that intake and exhaust vents for attics and enclosed rafter assemblies be provided per the roof-ventilation provisions (see § 1202.2) and the vent product manufacturer’s installation instructions; this requirement is referenced directly in § 1503.4. For chimneys or other roof penetrations wider than 30 inches (measured perpendicular to the slope), the CBC requires a cricket (saddle) on the ridge side, and the cricket covering must be sheet metal or the same material as the roof covering (§ 1503.5).
Requirements in detail
Attic and enclosed rafter ventilation (what the CBC says)
- Primary rule: Intake and exhaust vents for attic and enclosed rafter assemblies must be provided in accordance with § 1202.2 and the vent product manufacturer’s instructions (CBC § 1503.4).
- § 1202.2 (referenced by § 1503.4) gives the specific vent-area requirements and the unvented-attic alternative (see table below).
Cricket / saddle around wide penetrations (what the CBC says)
- Primary rule: A cricket or saddle shall be installed on the ridge side of any chimney or penetration greater than 30 inches (762 mm) wide, measured perpendicular to the slope; cricket/saddle coverings must be sheet metal or match the roof covering (§ 1503.5). The code also provides an exception allowing some factory skylights to be installed without a cricket when installed and flashed per the manufacturer’s instructions.
Decision-relevant dimensions & values
| Issue | Decision rule or value | Code Reference |
|---|---|---|
| When ventilation is required for attics/enclosed rafters | Intake and exhaust vents must be provided per § 1202.2 | § 1503.4 ; § 1202.2 |
| Minimum net free ventilating area (standard) | 1/150 of the area of the vented space (net free area) | § 1202.2 (net area requirement) |
| Reduced venting option (exception) | 1/300 of the area of the vented space if conditions met (vapor retarder in CZ 6–8 and 40–50% upper vents) | § 1202.2 exception |
| Cricket / saddle trigger width | Any chimney or penetration > 30 inches (762 mm) measured perpendicular to the slope requires a cricket | § 1503.5 |
| Cricket covering material | Sheet metal or the same material as the roof covering | § 1503.5 |
| Exception for unit skylights | Unit skylights flashed per manufacturer may be installed without a cricket | § 1503.5 exception |
Note: § 1503.4 points to § 1202.2 for the detailed ventilation metrics (vent area, unvented alternatives, and installation details).
Where the CBC is silent or terse
- § 1503.5 establishes the 30‑inch threshold and acceptable covering materials but does not prescribe geometric cricket dimensions. For guidance on cricket geometry (typical height relative to penetration width and roof slope), the Residential Code provides prescriptive cricket dimensions (see R1003.20), which many practitioners use for sizing; the CBC itself does not include those dimension tables. If you rely on the IRC/R-code figure, use it only as a practical guide unless your jurisdiction explicitly adopts the IRC detail.
Exceptions & special cases
- Unvented attics and unvented enclosed rafter assemblies are permitted where the unvented-attic conditions in § 1202.3 are met. In that case the ventilation provisions of § 1202.2 (and therefore the ventilation requirement cited by § 1503.4) do not apply.
- Unit skylights that are installed in accordance with their manufacturer’s instructions and Section 2405.5 (Residential code references) may be installed without a cricket/saddle — CBC § 1503.5 includes that exception. Check the skylight manufacturer’s flashing instructions and local enforcement policy.
- The CBC text for crickets prescribes covering materials but not the detailed shape or minimum height; if your project requires explicit dimensions (for flashing, drainage or fabrication), consult the residential detail R1003.20 or an accepted industry practice as permitted by the local building official.
Common mistakes
- Assuming every penetration needs a cricket: CBC requires a cricket only for penetrations wider than 30 inches measured perpendicular to the slope (§ 1503.5). Small chimneys, vents and most skylights generally do not trigger this requirement unless they exceed that width.
- Forgetting to size ventilation by net free area: Designers sometimes count gross opening area instead of net free ventilating area and fail to meet the 1/150 (or 1/300 exception) requirement in § 1202.2. Always use net free-vent area per manufacturer ratings.
- Omitting the ridge/upper vent proportion when using the 1/300 reduction: The reduced 1/300 ratio requires 40–50% of venting in the upper portion of the attic; failing to provide the correct upper/lower distribution invalidates the reduced-area exception.
- Overlooking the flashing relation: A cricket intersection must be flashed and counter-flashed like other roof–chimney intersections — the CBC requires proper flashing at roof openings (§ 1503.2), so coordinate cricket flashing with general flashing requirements.
Worked example — concrete scenario
Scenario: A residence has an enclosed attic with a floor area of 1,800 ft² and a masonry chimney whose narrow dimension (perpendicular to the slope) is 48 inches (4 ft). Roof slope is 6:12. The project will use a venting scheme with standard ventilation (no reduced 1/300 option).
Ventilation required:
- Net free ventilating area required = attic area / 150 = 1,800 ft² / 150 = 12.0 ft² net free area (equivalently 1,728 in²). This requirement comes from § 1202.2 as referenced in § 1503.4. Provide intake and exhaust so the net free area totals ≥12.0 ft² and follow manufacturer NFAs.
- If you were to use the reduced 1/300 option (only allowed when the conditions in § 1202.2 exception are satisfied), required net area would be 6.0 ft² — but those conditions (vapor retarder and 40–50% upper vents in CZ 6–8) must be met.
Cricket requirement:
- Chimney width = 48 in > 30 in, so a cricket/saddle is required on the ridge side per § 1503.5. Provide cricket covering in sheet metal or same roof material.
- The CBC does not give the cricket height formula. If you adopt the typical prescriptive geometry (from R1003.20 for example), for a 6:12 slope the cricket height H is commonly sized at 1/4 of the chimney width (H = 1/4 × W). For W = 48 in, H = 12 in (this is a residential-code detail used for sizing; CBC § 1503.5 itself does not include H = 1/4 × W). Confirm with the local code official before final fabrication.
Related provisions
- § 1503.4 — Attic and rafter ventilation (requires vents per § 1202.2 and manufacturer’s instructions).
- § 1503.5 — Crickets and saddles (cricket required for penetrations > 30 in; covering material requirement and skylight exception).
- § 1202.2 — Roof ventilation (net free area ratios, unvented alternatives, upper/lower vent distribution) — cited by § 1503.4 for venting metrics.
- § 1503.2 / § 1503.2.1 — Flashing requirements around roof openings (coordinate cricket flashing with these requirements).
- (For prescriptive cricket geometry used in practice) R1003.20 — Residential cricket dimensions table and figure (useful guidance, not a CBC dimension table).
Code references
Grounded in the retrieved California Building Code — click a citation to read the verbatim passage:
CBC § 1503.2 High relevance — show source text
1503.2 Flashing. Flashing shall be installed in such a manner so as to prevent water from entering the wall and roof through joints in copings, through moisture-permeable materials and at intersections with parapet walls and other penetrations through the roof plane.
1503.2.1 Locations. Flashing shall be installed at wall and roof intersections, at gutters, wherever there is a change in roof slope or direction and around roof openings. Where flashing is of metal, the metal shall be corrosion resistant with a thickness of not less than 0.019 inch (0.483 mm) (No. 26 galvanized sheet).
1503.3 Parapet walls. Parapet walls shall be coped or covered in accordance with Sections 1503.3.1 and 1503.3.2. The top surface of the parapet wall shall provide positive drainage.
1503.3.1 Fire-resistance-rated parapet walls. Parapet walls required by Section 705.12 shall be coped or covered with weatherproof materials of a width not less than the thickness of the parapet wall such that the fire-resistance rating of the wall is not decreased.
1503.3.2 Other parapet walls. Parapet walls meeting one of the exceptions in Section 705.12 shall be coped or covered with weatherproof materials of a width not less than the thickness of the parapet wall.
1503.4 Attic and rafter ventilation. Intake and exhaust vents for ventilation of attic and enclosed rafter assemblies shall be provided in accordance with Section 1202.2 and the vent product manufacturer’s installation instructions.
Exception: Unvented attic and unvented enclosed rafter assemblies in accordance with Section 1202.3.
1503.5 Crickets and saddles. A cricket or saddle shall be installed on the ridge side of any chimney or penetration greater than 30 inches (762 mm) wide as measured perpendicular to the slope. Cricket or saddle coverings shall be sheet metal or of the same material as the roof covering.
Exception: Unit skylights installed in accordance with Section 2405.5 and flashed in accordance with the manufacturer’s instructions shall be permitted to be installed without a cricket or saddle.
SECTION 1504—PERFORMANCE REQUIREMENTS
1504.1 Wind resistance of roofs. Roof decks and roof coverings shall be designed in accordance with Section 1504.
2025 CALIFORNIA BUILDING CODE 15-3
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ROOF ASSEMBLIES AND ROOFTOP STRUCTURES
1504.2 Wind resistance of asphalt shingles. Asphalt shingles shall be tested in accordance with ASTM D7158. Asphalt shingles shall meet the classification requirements of Table 1504.2 for the appropriate maximum basic wind speed. Asphalt shingle packaging shall bear a label to indicate compliance with ASTM D7158 and the required classification in Table 1504.2.
Exception: Asphalt shingles not included in the scope of ASTM D7158 shall be tested and labeled in accordance with ASTM D3161. Asphalt shingle packaging shall bear a label to indicate compliance with ASTM D3161 and the required classification in Table 1504.2.
CBC § 1202.3. High relevance — show source text
Exception: Unvented attic and unvented enclosed rafter assemblies in accordance with Section 1202.3.
1503.5 Crickets and saddles. A cricket or saddle shall be installed on the ridge side of any chimney or penetration greater than 30 inches (762 mm) wide as measured perpendicular to the slope. Cricket or saddle coverings shall be sheet metal or of the same material as the roof covering.
Exception: Unit skylights installed in accordance with Section 2405.5 and flashed in accordance with the manufacturer’s instructions shall be permitted to be installed without a cricket or saddle.
SECTION 1504—PERFORMANCE REQUIREMENTS
1504.1 Wind resistance of roofs. Roof decks and roof coverings shall be designed in accordance with Section 1504.
2025 CALIFORNIA BUILDING CODE 15-3
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ROOF ASSEMBLIES AND ROOFTOP STRUCTURES
1504.2 Wind resistance of asphalt shingles. Asphalt shingles shall be tested in accordance with ASTM D7158. Asphalt shingles shall meet the classification requirements of Table 1504.2 for the appropriate maximum basic wind speed. Asphalt shingle packaging shall bear a label to indicate compliance with ASTM D7158 and the required classification in Table 1504.2.
Exception: Asphalt shingles not included in the scope of ASTM D7158 shall be tested and labeled in accordance with ASTM D3161. Asphalt shingle packaging shall bear a label to indicate compliance with ASTM D3161 and the required classification in Table 1504.2.
TABLE 1504.2—CLASSIFICATION OF STEEP SLOPE ROOF SHINGLES TESTED IN ACCORDANCE WITH ASTM D3161 OR D7158 Col2 Col3 Col4 MAXIMUM BASIC WIND SPEED,****V, FROM
FIGURES 1609.3(1)–(4) OR ASCE 7 (mph)MAXIMUM ALLOWABLE STRESS DESIGN WIND
SPEED,****Vasd, FROM Table 1609.3.1 (mph)**ASTM D7158a **
CLASSIFICATIONASTM D3161 or
UL 7103 CLASSIFICATION110 85 D, G or H A, D or F 116 90 D, G or H A, D or F 129 100 G or H A, D or F 142 110 G or H F 155 120 G or H F 168 130 H F 181 140 H F 194 150 H F For SI: 1 foot = 304.8 mm, 1 mph = 0.447 m/s.
a. The standard calculations contained in ASTM D7158 assume Exposure Category B or C and building height of 60 feet or less. Additional calculations are required for condi-
tions outside of these assumptions.For SI: 1 foot = 304.8 mm, 1 mph = 0.447 m/s.
a. The standard calculations contained in ASTM D7158 assume Exposure Category B or C and building height of 60 feet or less.CBC § 1.1 High relevance — show source text
Openings in roof framing members shall conform to the requirements of Section R802.7. Required ventilation openings shall open directly to the outside air and shall be protected to prevent the entry of birds, rodents, snakes and other similar creatures.
R806.1.1 Vents in the Wildland Urban Interface (WUI). Where provided, ventilation openings for enclosed attics, gable ends, ridge ends, under eaves and cornices, enclosed eave soffit spaces, enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters, underfloor ventilation, foundations and crawl spaces, or any other opening intended to permit ventilation, either in a horizontal or vertical plane, shall be in accordance with Part 7, California Wildland-Urban Interface Code to resist building ignition from the intrusion of burning embers and flame through the ventilation openings. R806.2 Minimum vent area. The minimum net free ventilating area shall be [1] / 150 of the area of the vented space. Exception: The minimum net free ventilation area shall be [1] / 300 of the vented space provided both of the following conditions are met:
- In Climate Zones 6, 7 and 8, a Class I or II vapor retarder is installed on the warm-in-winter side of the ceiling.
- Not less than 40 percent and not more than 50 percent of the required ventilating area is provided by ventilators located in the upper portion of the attic or rafter space. Upper ventilators shall be located not more than 3 feet (914 mm) below the ridge or highest point of the space, measured vertically. The balance of the required ventilation provided shall be located in the bottom one-third of the attic space. Where the location of wall or roof framing members conflicts with the installation of upper ventilators, installation more than 3 feet (914 mm) below the ridge or highest point of the space shall be permitted.
R806.3 Vent and insulation clearance. Where eave or cornice vents are installed, blocking, bridging and insulation shall not block the free flow of air. Not less than a 1-inch (25 mm) space shall be provided between the insulation and the roof sheathing and at the location of the vent.
R806.4 Installation and weather protection. Ventilators shall be installed in accordance with manufacturer’s instructions. Installation of ventilators in roof systems shall be in accordance with the requirements of Section R903. Installation of ventilators in wall systems shall be in accordance with the requirements of Section R703.1.
R806.5 Unvented attic and unvented enclosed rafter assemblies. Unvented attics and unvented enclosed roof framing assemblies created by ceilings that are applied directly to the underside of the roof framing members and structural roof sheathing applied directly to the top of the roof framing members/rafters, shall be permitted where all the following conditions are met:
- The unvented attic space is completely within the building thermal envelope.
- Interior Class I vapor retarders are not installed on the ceiling side (attic floor) of the unvented attic assembly or on the ceiling side of the unvented enclosed roof framing assembly.
- Where wood shingles or shakes are used, a minimum [1] / 4 -inch (6.4 mm) vented airspace separates the shingles or shakes and the roofing underlayment above the structural sheathing.
CBC § 3.8 High relevance — show source text
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ROOF-CEILING CONSTRUCTION
R804.3.8 Roof tie-down. Roof assemblies shall be connected to walls below in accordance with Table R804.3. A continuous load path shall be provided to transfer uplift loads to the foundation.
SECTION R805—CEILING FINISHES
R805.1 Ceiling installation. Ceilings shall be installed in accordance with the requirements for interior wall finishes as provided in Sections R702.1 through R702.6.
SECTION R806—ROOF VENTILATION
Note: The IECC climate zones used by this section differ from those used by the California Energy Code to determine applicability of energy efficiency measures. Comparison of IECC and California Energy Code climate zones is shown in Table R702.7.3.
R806.1 Ventilation required. Enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters shall have cross ventilation for each separate space by ventilating openings protected against the entrance of rain or snow. Ventilation openings shall have a least dimension of [1] / 16 inch (1.6 mm) minimum and [1] / 4 inch (6.4 mm) maximum. Ventilation openings having a least dimension larger than [1] / 4 inch (6.4 mm) shall be provided with corrosion-resistant wire cloth screening, hardware cloth, perforated vinyl or similar material with openings having a least dimension of [1] / 16 inch (1.6 mm) minimum and [1] / 4 inch (6.4 mm) maximum. Openings in roof framing members shall conform to the requirements of Section R802.7. Required ventilation openings shall open directly to the outside air and shall be protected to prevent the entry of birds, rodents, snakes and other similar creatures.
R806.1.1 Vents in the Wildland Urban Interface (WUI). Where provided, ventilation openings for enclosed attics, gable ends, ridge ends, under eaves and cornices, enclosed eave soffit spaces, enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters, underfloor ventilation, foundations and crawl spaces, or any other opening intended to permit ventilation, either in a horizontal or vertical plane, shall be in accordance with Part 7, California Wildland-Urban Interface Code to resist building ignition from the intrusion of burning embers and flame through the ventilation openings. R806.2 Minimum vent area. The minimum net free ventilating area shall be [1] / 150 of the area of the vented space. Exception: The minimum net free ventilation area shall be [1] / 300 of the vented space provided both of the following conditions are met:
- In Climate Zones 6, 7 and 8, a Class I or II vapor retarder is installed on the warm-in-winter side of the ceiling.
- Not less than 40 percent and not more than 50 percent of the required ventilating area is provided by ventilators located in the upper portion of the attic or rafter space. Upper ventilators shall be located not more than 3 feet (914 mm) below the ridge or highest point of the space, measured vertically. The balance of the required ventilation provided shall be located in the bottom one-third of the attic space.
CBC § 1202.1 High relevance — show source text
SECTION 1202—VENTILATION
1202.1 General. Buildings shall be provided with natural ventilation in accordance with Section 1202.5, or mechanical ventilation in accordance with the California Mechanical Code .
Dwelling units complying with the air leakage requirements of the California Energy Code or ASHRAE 90.1 shall be ventilated by mechanical means in accordance with Section 403 of the California Mechanical Code . Ambulatory care facilities and Group I-2 occupancies shall be ventilated by mechanical means in accordance with Section 407 of the California Mechanical Code .
1202.2 Roof ventilation. Roof assemblies shall be ventilated in accordance with this section or shall comply with Section 1202.3.
1202.2.1 Ventilated attics and rafter spaces. Enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof framing members shall have cross ventilation for each separate space by ventilation openings protected against the entrance of rain and snow. Blocking and bridging shall be arranged so as not to interfere with the movement of air. An airspace of not less than 1 inch (25 mm) shall be provided between the insulation and the roof sheathing. The net free ventilating area shall be not less than [1] / 150 of the area of the space ventilated. Ventilators shall be installed in accordance with manufacturer’s installation instructions.
Exception: The net free cross-ventilation area shall be permitted to be reduced to [1] / 300 provided both of the following conditions are met:
- In Climate Zones 6, 7 and 8, a Class I or II vapor retarder is installed on the warm-in-winter side of the ceiling.
- At least 40 percent and not more than 50 percent of the required venting area is provided by ventilators located in the upper portion of the attic or rafter space. Upper ventilators shall be located not more than 3 feet (914 mm) below the ridge or highest point of the space, measured vertically, with the balance of the ventilation provided by eave or cornice vents. Where the location of wall or roof framing members conflicts with the installation of upper ventilators, installation more than 3 feet (914 mm) below the ridge or highest point of the space shall be permitted.
1202.2.2 Openings into attic. Exterior openings into the attic space of any building intended for human occupancy shall be protected to prevent the entry of birds, squirrels, rodents, snakes and other similar creatures. Openings for ventilation having a least dimension of not less than [1] / 16 inch (1.6 mm) and not more than [1] / 4 inch (6.4 mm) shall be permitted. Openings for ventilation having a least dimension larger than [1] / 4 inch (6.4 mm) shall be provided with corrosion-resistant wire cloth screening, hardware cloth, perforated vinyl or similar material with openings having a least dimension of not less than [1] / 16 inch (1.6 mm) and not more than [1] / 4 inch (6.4 mm). Where combustion air is obtained from an attic area, it shall be in accordance with Chapter 7 of the California Mechanical Code .
1202.3 Unvented attic and unvented enclosed rafter assemblies. Unvented attics and unvented enclosed roof framing assemblies created by ceilings applied directly to the underside of the roof framing members/rafters and the structural roof sheathing at the top of the roof framing members shall be permitted where all of the following conditions are met: 1.
CBC § 0.024 High relevance — show source text
024 inch (nominal 24
gauge) sheet metal over 1
inch glass fiber or min-
eral wool batts reinforced
with wire on rear face
with ventilated air space|18|12|9|6|6|4|5|3|3|3| |(4) 31⁄2 inch thick masonry
wall with ventilated air
space|––|12|––|6|––|6|––|6|––|6| |(5) 0.024 inch (nominal 24
gauge) sheet metal with
ventilated air space|18|12|9|6|6|4|5|3|3|2| |(6) 1⁄2 of an inch thick insula-
tion board with ventilated
air space|18|12|9|6|6|4|5|3|3|3| |(7) 0.024 inch (nominal 24
gauge) sheet metal with
ventilated air space over
0.024 inch (nominal 24
gauge) sheet metal with
ventilated air space|18|12|9|6|6|4|5|3|3|3| |(8) 1 inch glass fiber or
mineral wool batts sand-
wiched between two
sheets 0.024 inch (nom-
inal 24 gauge) sheet
metal with ventilated air
space|18|12|9|6|6|4|5|3|3|3|For SI units: 1 inch = 25.4 mm
Notes:
1 Reduction of clearances from combustible materials shall not interfere with combustion air, draft hood clearance and relief, and accessibility of servicing. 2 All clearances shall be measured from the outer surface of the combustible material to the nearest point on the surface of the appliance, disregarding any intervening protection applied to the combustible material. 3 Spacers and ties shall be of noncombustible material. No spacer or tie shall be used directly opposite the appliance or connector. 4 Where all clearance reduction systems use a ventilated air space, adequate provision for air circulation shall be provided as described. [See Figure 303.10.1(2) and Figure 303.10.1(3)] 5 At least 1 inch (25.4 mm) shall be between clearance reduction systems and combustible walls and ceilings for reduction systems using a ventilated air space. 6 Where a wall protector is installed on a single flat wall away from corners, it shall have a minimum 1 inch (25.4 mm) air gap. To provide adequate air circulation, the bottom and top edges, or only the side and top edges, or all edges shall be left open. 7 Mineral wool batts (blanket or board) shall have a minimum density of 8 pounds per cubic foot (lb/ft 3 ) (128 kg/m 3 ) and a minimum melting point of 1500°F (816°C). 8 Insulation material used as part of a clearance reduction system shall have a thermal conductivity of 1.0 British thermal unit inch per hour square foot degree Fahrenheit [Btu•in/(h•ft [2] - °F)] [0.1W/(m•K)] or less. 9 At least 1 inch (25.4 mm) shall be between the appliance and the protector. The clearance between the appliance and the combustible surface shall not be reduced below that allowed in Table 303.10.1. 10 All clearances and thicknesses are minimum; larger clearances and thicknesses are acceptable.
CBC § 2308.11.2 Medium relevance — show source text
The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the
bearing walls, such as rafter ties, is provided at that location. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the
adjustment factors in Table 2308.11.2(7).|Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.
a. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the
bearing walls, such as rafter ties, is provided at that location. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the
adjustment factors in Table 2308.11.2(7).|Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.
a. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the
bearing walls, such as rafter ties, is provided at that location. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the
adjustment factors in Table 2308.11.2(7).|Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.
a. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the
bearing walls, such as rafter ties, is provided at that location. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the
adjustment factors in Table 2308.11.2(7).|Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.
a. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the
bearing walls, such as rafter ties, is provided at that location. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the
adjustment factors in Table 2308.11.2(7).|2025 CALIFORNIA BUILDING CODE 23-75
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CBC § 25.4 Medium relevance — show source text
Span exceeds 26 feet in length.|Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.
a. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the
bearing walls, such as rafter ties, is provided at that location. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the
adjustment factors in Table 2308.11.2(7).
b. Span exceeds 26 feet in length.|Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.
a. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the
bearing walls, such as rafter ties, is provided at that location. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the
adjustment factors in Table 2308.11.2(7).
b. Span exceeds 26 feet in length.|Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.
a. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the
bearing walls, such as rafter ties, is provided at that location. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the
adjustment factors in Table 2308.11.2(7).
b. Span exceeds 26 feet in length.|Check sources for availability of lumber in lengths greater than 20 feet.
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 pound per square foot = 0.0479 kPa.
a. The tabulated rafter spans assume that ceiling joists are located at the bottom of the attic space or that some other method of resisting the outward push of the rafters on the
bearing walls, such as rafter ties, is provided at that location. Where ceiling joists or rafter ties are located higher in the attic space, the rafter spans shall be multiplied by the
adjustment factors in Table 2308.11.2(7).
b. Span exceeds 26 feet in length.|23-70 2025 CALIFORNIA BUILDING CODE
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|TABLE 2308.11.2(5)—RAFTER SPANS FOR COMMON LUMBER SPECIES
(Allowable stress design ground snow load, p = 30 psf, ceiling attached to rafters, L/Δ =CBC § 1501.1 Medium relevance — show source text
ICC code development note: Code change proposals to sections preceded by the designation [BF] or [P] will be considered by one of the code development committees meeting during the 2024 (Group A) Code Development Cycle. All other code change proposals will be considered by a code development committee meeting during the 2025 (Group B) Code Development Cycle.
SECTION 1501—GENERAL
1501.1 Scope. The provisions of this chapter shall govern the design, materials, construction and quality of roof assemblies, and rooftop structures.
SECTION 1502—ROOF DRAINAGE
[P] 1502.1 General. Design and installation of roof drainage systems shall comply with this section, Section 1611 of this code and Chapter 11 of the California Plumbing Code .
[P] 1502.2 Secondary (emergency overflow) drains or scuppers. Where roof drains are required, secondary (emergency overflow) roof drains or scuppers shall be provided where the roof perimeter construction extends above the roof in such a manner that water will be entrapped if the primary drains allow buildup for any reason. The installation and sizing of secondary emergency overflow drains, leaders and conductors shall comply with Section 1611 of this code and Chapter 11 of the California Plumbing Code .
1502.3 Gutters. Gutters and leaders placed on the outside of buildings, other than Group R-3, private garages and buildings of Type V construction, shall be of noncombustible material or not less than Schedule 40 plastic pipe.
SECTION 1503—WEATHER PROTECTION
1503.1 General. Roof decks shall be covered with approved roof coverings secured to the building or structure in accordance with the provisions of this chapter. Roof coverings shall be designed in accordance with this code, and installed in accordance with this code and the manufacturer’s approved instructions.
1503.2 Flashing. Flashing shall be installed in such a manner so as to prevent water from entering the wall and roof through joints in copings, through moisture-permeable materials and at intersections with parapet walls and other penetrations through the roof plane.
1503.2.1 Locations. Flashing shall be installed at wall and roof intersections, at gutters, wherever there is a change in roof slope or direction and around roof openings. Where flashing is of metal, the metal shall be corrosion resistant with a thickness of not less than 0.019 inch (0.483 mm) (No. 26 galvanized sheet).
1503.3 Parapet walls. Parapet walls shall be coped or covered in accordance with Sections 1503.3.1 and 1503.3.2. The top surface of the parapet wall shall provide positive drainage.
1503.3.1 Fire-resistance-rated parapet walls. Parapet walls required by Section 705.12 shall be coped or covered with weatherproof materials of a width not less than the thickness of the parapet wall such that the fire-resistance rating of the wall is not decreased.
1503.3.2 Other parapet walls. Parapet walls meeting one of the exceptions in Section 705.12 shall be coped or covered with weatherproof materials of a width not less than the thickness of the parapet wall.
1503.4 Attic and rafter ventilation. Intake and exhaust vents for ventilation of attic and enclosed rafter assemblies shall be provided in accordance with Section 1202.2 and the vent product manufacturer’s installation instructions.
CBC § 2.1 Medium relevance — show source text
R903.2.1 Locations. Flashings shall be installed at wall and roof intersections, wherever there is a change in roof slope or direction and around roof openings. A flashing shall be installed to divert the water away from where the eave of a sloped roof intersects a vertical sidewall. Where flashing is of metal, the metal shall be corrosion resistant with a thickness of not less than 0.019 inch (0.5 mm) (No. 26 galvanized sheet).
R903.2.2 Crickets and saddles. A cricket or saddle shall be installed on the ridge side of any chimney or penetration more than 30 inches (762 mm) wide as measured perpendicular to the slope. Cricket or saddle coverings shall be sheet metal or of the same material as the roof covering.
Exception: Unit skylights installed in accordance with Section R324.6 and flashed in accordance with the manufacturer’s instructions shall be permitted to be installed without a cricket or saddle.
R903.3 Coping. Parapet walls shall be properly coped with noncombustible, weatherproof materials of a width not less than the thickness of the parapet wall.
R903.4 Roof drainage. Unless roofs are sloped to drain over roof edges, roof drains shall be installed at each low point of the roof.
R903.4.1 Secondary (emergency overflow) drains or scuppers. Where roof drains are required, secondary emergency overflow roof drains or scuppers shall be provided where the roof perimeter construction extends above the roof in such a manner that water will be entrapped if the primary drains allow buildup for any reason. Overflow drains having the same size as the roof drains shall be installed with the inlet flow line located 2 inches (51 mm) above the low point of the roof, or overflow scuppers having three times the size of the roof drains and having a minimum opening height of 4 inches (102 mm) shall be installed in the adjacent parapet walls with the inlet flow located 2 inches (51 mm) above the low point of the roof served. The installation and sizing of overflow drains, leaders and conductors shall comply with the California Plumbing Code .
SECTION R904—MATERIALS
R904.1 Scope. The requirements set forth in this section shall apply to the application of roof covering materials specified herein. Roof assemblies shall be applied in accordance with this chapter and the manufacturer’s installation instructions. Installation of roof assemblies shall comply with the applicable provisions of Section R905.
R904.2 Compatibility of materials. Roof assemblies shall be of materials that are compatible with each other and with the building or structure to which the materials are applied.
R904.3 Material specifications and physical characteristics. Roof covering materials shall conform to the applicable standards listed in this chapter.
R904.4 Product identification. Roof covering materials shall be delivered in packages bearing the manufacturer’s identifying marks and approved testing agency labels required. Bulk shipments of materials shall be accompanied by the same information issued in the form of a certificate or on a bill of lading by the manufacturer.
SECTION R905—REQUIREMENTS FOR ROOF COVERINGS
R905.1 Roof covering application. Roof coverings shall be applied in accordance with the applicable provisions of this section and the manufacturer’s installation instructions. Unless otherwise specified in this section, roof coverings shall be installed to resist the component and cladding loads specified in Table R301.2.1(1), adjusted for height and exposure in accordance with Table R301.2.1(2).
CBC § 304.8 Medium relevance — show source text
For residential subdivisions where all dwellings and townhouses are equipped throughout with an automatic sprinkler system installed in accordance with Section_R309_, the fire
separation distance for exterior walls not fire-resistance rated and for fire-resistance-rated projections shall be permitted to be reduced to 0 feet, and unlimited unprotected
openings and penetrations shall be permitted, where the adjoining lot provides an open setback yard that is 6 feet or more in width on the opposite side of the property line.
b. The fire-resistance rating shall be permitted to be reduced to 0 hours on the underside of the eave overhang if fireblocking is provided from the wall top plate to the underside
of the roof sheathing.
c. The fire-resistance rating shall be permitted to be reduced to 0 hours on the underside of the rake overhang where vent openings that communicate with the attic are not
installed in the overhang or gable wall.|For SI: 1 foot = 304.8 mm.
NA = Not Applicable.
a. For residential subdivisions where all dwellings and townhouses are equipped throughout with an automatic sprinkler system installed in accordance with Section_R309_, the fire
separation distance for exterior walls not fire-resistance rated and for fire-resistance-rated projections shall be permitted to be reduced to 0 feet, and unlimited unprotected
openings and penetrations shall be permitted, where the adjoining lot provides an open setback yard that is 6 feet or more in width on the opposite side of the property line.
b. The fire-resistance rating shall be permitted to be reduced to 0 hours on the underside of the eave overhang if fireblocking is provided from the wall top plate to the underside
of the roof sheathing.
c. The fire-resistance rating shall be permitted to be reduced to 0 hours on the underside of the rake overhang where vent openings that communicate with the attic are not
installed in the overhang or gable wall.|For SI: 1 foot = 304.8 mm.
NA = Not Applicable.
a. For residential subdivisions where all dwellings and townhouses are equipped throughout with an automatic sprinkler system installed in accordance with Section_R309_, the fire
separation distance for exterior walls not fire-resistance rated and for fire-resistance-rated projections shall be permitted to be reduced to 0 feet, and unlimited unprotected
openings and penetrations shall be permitted, where the adjoining lot provides an open setback yard that is 6 feet or more in width on the opposite side of the property line.
b. The fire-resistance rating shall be permitted to be reduced to 0 hours on the underside of the eave overhang if fireblocking is provided from the wall top plate to the underside
of the roof sheathing.
c. The fire-resistance rating shall be permitted to be reduced to 0 hours on the underside of the rake overhang where vent openings that communicate with the attic are not
installed in the overhang or gable wall.|R302.2 Townhouses. Walls separating townhouse units shall be constructed in accordance with Section R302.2.1 or R302.2.2 and shall comply with Sections R302.2.3 through R302.2.5.
R302.2.1 Double walls. Each townhouse unit shall be separated from other townhouse units by two 1-hour fire-resistance-rated wall assemblies tested in accordance with ASTM E119, UL 263 or Section 703.2.2 of the California Building Code.
3-24 2025 CALIFORNIA RESIDENTIAL CODE
Frequently asked questions
Do all chimneys require a cricket?
No — the CBC requires a cricket only where the chimney or penetration is greater than 30 inches (762 mm) wide as measured perpendicular to the slope; smaller penetrations do not trigger the mandatory cricket requirement (§ 1503.5).
How do I calculate how much attic ventilation I need?
Use the net free ventilating area ratios in § 1202.2: normally 1/150 of the attic area; the code allows 1/300 when the specified conditions are met (vapor retarder in certain climate zones and correct upper/lower vent distribution). § 1503.4 points you to § 1202.2 for these specifics.
Does the CBC prescribe the size/height of the cricket?
No — § 1503.5 requires a cricket for penetrations over 30 inches and prescribes acceptable covering materials but does not give a dimension table. Many practitioners reference the residential detail (R1003.20) for typical cricket geometry; confirm with the local official.
Can a factory skylight be installed without a cricket?
Yes — the CBC includes an exception allowing unit skylights flashed per the manufacturer’s instructions to be installed without a cricket (§ 1503.5 exception).
If I have an unvented attic, do these ventilation rules apply?
Not if the unvented-attic criteria of § 1202.3 are met; § 1503.4 explicitly refers to the ventilated requirement but excepts unvented attics constructed per § 1202.3.
More in California Building Code
- Administration & Permits
- Energy Efficiency
- Existing Buildings
- Occupancy Classification & Use
- Hazardous Materials & Occupancies
- Types of Construction
- Fire-Resistance & Fire Safety
- Interior Finishes
- Means of Egress
- Accessibility
- Exterior Walls
- Roofing & Roof Assemblies
- Structural Design
- Special Inspections & Tests
- Foundations & Soils
- Concrete
- Masonry
- Steel
- Wood
- Elevators & Conveying Systems
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