CBC · California Building Code

What are the wind and performance requirements for roof coverings and edge systems?

In plain terms: the CBC requires roofs and their edge details to be designed for the site wind speed. Asphalt shingles must be tested and labeled to the ASTM classes listed in Table 1504.2 (§ 1504.2), and metal edge systems on low‑slope roofs must be designed to Chapter 16 wind loads and tested per ANSI/SPRI ES‑1 (gutters have a separate SPRI test path) (§ 1504.6 and § 1504.6.1) .

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Last reviewed: July 5, 2026

What the code requires — 2–4 sentences

The California Building Code requires that roof decks and roof coverings be designed for wind resistance and that certain coverings and edge systems meet specified test/classification requirements. Specifically, roof coverings and their performance are governed by § 1504.1, asphalt shingles by § 1504.2, and low‑slope roof edge systems by § 1504.6. These sections require testing or design for the applicable basic wind speed and reference specific test standards and Chapter 16 load rules for determining design wind (see § 1504.1, § 1504.2 and § 1504.6) .

Requirements in detail

1) General rule: Roofs must be designed for wind

Rule: Roof decks and roof coverings shall be designed in accordance with Section 1504 (i.e., wind resistance is mandatory) — § 1504.1 .
Practical effect: The roof system must resist the design wind pressures established in Chapter 16 (basic wind speed, exposure, pressure zones) when applicable (see cross‑references in Chapter 16).

2) Asphalt shingles — tests and labeling (§ 1504.2)

Rule: Asphalt shingles must be tested to ASTM D7158 and meet the classification in Table 1504.2 for the applicable maximum basic wind speed; packaging must bear a label showing compliance. If a shingle is outside ASTM D7158 scope, ASTM D3161 is permitted as an alternate test and labeling is required — § 1504.2 .
What to check on product: Packaging label showing ASTM D7158 (and the D7158 class) or ASTM D3161/UL classification as required by Table 1504.2.

Decision table (steep‑slope shingle classifications from Table 1504.2)

Decision item	Required value / test	Code Reference
Test standard required for most asphalt shingles	ASTM D7158 and labeling showing the D7158 class	§ 1504.2
Alternate test (where D7158 not applicable)	ASTM D3161 or UL 7103 labeling per Table 1504.2	§ 1504.2 (exception)
Minimum D7158 class for V = 142 mph basic wind speed	D7158 class G or H (see Table 1504.2)	Table 1504.2, § 1504.2

(Use Table 1504.2 to map the project’s basic wind speed V to the required ASTM class; the table and § 1504.2 show the full mapping) .

3) Edge systems for low‑slope roofs (§ 1504.6 and § 1504.6.1)

Rule: Metal edge systems (except gutters and counterflashing) installed on built‑up, modified bitumen and single‑ply low‑slope roofs must be designed and installed for wind loads per Chapter 16 and tested for resistance using Test Methods RE‑1, RE‑2 and RE‑3 of ANSI/SPRI ES‑1. The basic wind speed used for those tests must be determined from the wind maps in Section 1609 (Figures 1609.3(1)–(4)) — § 1504.6 .
Gutters used to secure the membrane: must be designed to resist wind loads per Section 1609 and tested to SPRI GT‑1 Test Methods G‑1 and G‑2 — § 1504.6.1 .

Quick reference (edge systems)

Decision item	Required action / test	Code Reference
Metal edge systems on low‑slope built‑up, modified bitumen, single‑ply	Design for Chapter 16 wind loads; test per ANSI/SPRI ES‑1 (RE‑1/RE‑2/RE‑3) with V from Figures 1609.3	§ 1504.6
Gutters securing membrane	Design per Section 1609 wind loads; test per SPRI GT‑1 (G‑1, G‑2)	§ 1504.6.1

4) Other related performance rules referenced in Section 1504

The code links roof covering wind performance to the roof system wind provisions in Chapter 16 (see Section 1609.6 and related subsections on roof systems and roof coverings). For example, § 1609.6.2 requires roof coverings to be designed for the roof system pressures; asphalt shingle cross‑reference to § 1504.2 appears in 1609.6.2.1 — see Chapter 16 references .

Exceptions & special cases

Asphalt shingle alternate testing: If a shingle is outside the scope of ASTM D7158, the code allows testing and labeling under ASTM D3161 instead (see exception in § 1504.2) .
Edge scope exclusion: § 1504.6 explicitly excludes gutters and counterflashing from the general edge‑system testing requirement; gutters used to secure membrane have their own test requirement (§ 1504.6.1) .
Ballasted systems: Ballasted single‑ply low‑slope roofs are treated differently (design per ANSI/SPRI RP‑4) — referenced in § 1504.5 (note: not one of the three controlling sections you asked about, but important where ballasted systems are used) .

If a specific roofing material or assembly is not covered in full by § 1504.1, § 1504.2 or § 1504.6 (for example, rigid tile wind uplift moment equations and special testing), the code points you to other sections (e.g., § 1504.3 for clay/concrete tile and Chapter 16 for rigid tile uplift calculations). I relied only on text retrieved from the provided CBC excerpts; if you want verbatim language or other sections, I can fetch those next.

Common mistakes

Accepting product literature that does not show the required ASTM test standard and class on the packaging — § 1504.2 requires packaging labeling showing compliance with the correct ASTM classification .
Applying ES‑1 edge testing without using the correct basic wind speed (V) from Figures 1609.3 — § 1504.6 requires basic wind speed to be determined from those figures for ES‑1 testing .
Treating gutters and counterflashing the same as metal edge flashings — the code excludes them from the general edge‑system tests and gives gutters a separate test path (§ 1504.6 and § 1504.6.1) .
Using the wrong ASTM test: confusing ASTM D7158 (wind classification for shingles) with ASTM D3161 (impact/wind for some shingle types) or UL/ FM standards used for other membranes — check § 1504.2 and the tables carefully .

Worked example — concrete scenario with numbers

Scenario: A commercial steep‑slope roof in California is located in a site where the basic wind speed from Figures 1609.3 is V = 142 mph. The owner wants to use asphalt shingles.

Step 1 — Shingle classification required:

Look up V = 142 mph in Table 1504.2. For V = 142 mph the table requires ASTM D7158 classification G or H for steep‑slope shingles. Therefore the installer must select shingles whose packaging shows compliance with ASTM D7158 and the D7158 class G or H (per § 1504.2) .

Step 2 — Verify labeling:

Confirm the shingle package carries an ASTM D7158 label with class G or H, or (only if the product is outside D7158 scope) an ASTM D3161/UL label matching the table entry — § 1504.2 (and its exception) .

Step 3 — Edge and gutters (if low‑slope portions present):

If the building also has adjacent low‑slope roof areas with metal edge systems, those edge systems must be designed for the Chapter 16 wind loads corresponding to V = 142 mph and tested per ANSI/SPRI ES‑1 (RE‑1/RE‑2/RE‑3) using that wind speed — § 1504.6 .
If gutters are used to secure a low‑slope membrane, they must be tested per SPRI GT‑1 (G‑1 and G‑2) and designed per Section 1609 wind loads — § 1504.6.1 .

This shows how to turn the basic wind speed (from Chapter 16 maps) into a material selection and test requirement under § 1504.2 and § 1504.6.

Related provisions (direct references you should also check)

§ 1504.1 — Wind resistance of roofs (general requirement)
§ 1504.2 — Wind resistance, asphalt shingles (tests/labeling and Table 1504.2)
§ 1504.3 — Wind resistance and testing requirements for clay and concrete tile (overturning, wind tunnel, lift coefficient)
§ 1504.4 — Wind resistance of nonballasted roofs and referenced test standards (FM, UL, ASTM)
§ 1504.5 — Ballasted low‑slope single‑ply roof systems (ANSI/SPRI RP‑4)
§ 1504.6 and § 1504.6.1 — Edge systems and gutter securement for low‑slope roofs (ANSI/SPRI ES‑1 and SPRI GT‑1)
Chapter 16 (Section 1609 and 1609.6) — How to determine basic wind speed, exposure, and roof system pressures used to size and test coverings and edges — see § 1609.6 and 1609.6.2.1 for links to § 1504.2 and roof covering design

Code references

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

CBC § 1504.3.1.3 High relevance — show source text
1504.3.1.3 Air permeability testing. The lift coefficient for concrete and clay tile shall be 0.2 or shall be determined in accordance with SBCCI SSTD 11 or ASTM C1570.

1504.4 Wind resistance of nonballasted roofs. Roof coverings installed on roofs in accordance with Section 1507 that are mechanically attached or adhered to the roof deck shall be designed to resist the design wind load pressures for components and cladding in accordance with Section 1609.6.2. The wind load on the roof covering shall be permitted to be determined using allowable stress design.

1504.4.1 Other roof systems. Built-up, modified bitumen, fully adhered or mechanically attached single-ply roof systems, metal panel roof systems applied to a solid or closely fitted deck and other types of membrane roof coverings shall be tested in accordance with FM 4474, UL 580 or UL 1897.

1504.4.2 Structural metal panel roof systems. Where the metal roof panel functions as the roof deck and roof covering and it provides both weather protection and support for loads, the structural metal panel roof system shall comply with this section. Structural standing-seam metal panel roof systems shall be tested in accordance with ASTM E1592 or FM 4474. Structural through-fastened metal panel roof systems shall be tested in accordance with ASTM E1592, FM 4474 or UL 580.

Exceptions:
1. Metal roofs constructed of cold-formed steel shall be permitted to be designed and tested in accordance with the applicable referenced structural design standard in Section 2204.1.
2. Metal roofs constructed of aluminum shall be permitted to be designed and tested in accordance with the applicable referenced structural design standard in Section 2002.1.
1504.4.3 Metal roof shingles. Metal roof shingles applied to a solid or closely fitted deck shall be tested in accordance with ASTM D3161, FM 4474, UL 580 or UL 1897. Metal roof shingles tested in accordance with ASTM D3161 shall meet the classification requirements of Table 1504.2 for the appropriate maximum basic wind speed and the metal shingle packaging shall bear a label to indicate compliance with ASTM D3161 and the required classification in Table 1504.2.

1504.4.4 Slate shingles. Slate shingles shall be tested in accordance with ASTM D3161. Slate packaging shall bear a label indicating compliance with ASTM D3161 and the required classification in Table 1504.2.

1504.5 Ballasted low-slope single-ply roof systems. Ballasted low-slope single-ply roof system coverings installed in accordance with Section 1507.12 shall be designed in accordance with ANSI/SPRI RP-4.

1504.6 Edge systems for low-slope roofs. Metal edge systems, except gutters and counterflashing, installed on built-up, modified bitumen and single-ply roof systems on a low-slope roof shall be designed and installed for wind loads in accordance with Chapter 16

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ROOF ASSEMBLIES AND ROOFTOP STRUCTURES

and tested for resistance in accordance with Test Methods RE-1, RE-2 and RE-3 of ANSI/SPRI ES-1, except basic wind speed, V, shall be determined from Figures 1609.3(1)through 1609.3(4), as applicable.
CBC § 1504.4.4 High relevance — show source text
1504.4.4 Slate shingles. Slate shingles shall be tested in accordance with ASTM D3161. Slate packaging shall bear a label indicating compliance with ASTM D3161 and the required classification in Table 1504.2.

1504.5 Ballasted low-slope single-ply roof systems. Ballasted low-slope single-ply roof system coverings installed in accordance with Section 1507.12 shall be designed in accordance with ANSI/SPRI RP-4.

1504.6 Edge systems for low-slope roofs. Metal edge systems, except gutters and counterflashing, installed on built-up, modified bitumen and single-ply roof systems on a low-slope roof shall be designed and installed for wind loads in accordance with Chapter 16

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and tested for resistance in accordance with Test Methods RE-1, RE-2 and RE-3 of ANSI/SPRI ES-1, except basic wind speed, V, shall be determined from Figures 1609.3(1)through 1609.3(4), as applicable.

1504.6.1 Gutter securement for low-slope roofs. Gutters that are used to secure the perimeter edge of the roof membrane on low-slope built-up, modified bitumen, and single-ply roofs, shall be designed, constructed and installed to resist wind loads in accordance with Section 1609 and shall be tested in accordance with Test Methods G-1 and G-2 of SPRI GT-1.

1504.7 Impact resistance. Roof coverings installed on low-slope roofs in accordance with Section 1507 shall resist impact damage based on the results of tests conducted in accordance with ASTM D3746, ASTM D4272 or the “Resistance to Foot Traffic Test” in FM 4470.

1504.8 Wind resistance of aggregate-surfaced roofs. Parapets shall be provided for aggregate surfaced roofs and shall comply with Table 1504.8. Such parapets shall be provided on the perimeter of the roof at all exterior sides except where an adjacent wall extends above the roof to a height at least equivalent to that required for the parapet. For roofs with differing surface elevations due to slope or sections at different elevations, the minimum parapet height shall be determined based on each roof surface elevation, and at no point shall the parapet height be less than that required by Table 1504.8.

Exception: Ballasted single-ply roof coverings shall be designed and installed in accordance with Section 1504.5.

|TABLE 1504.8—MINIMUM REQUIRED PARAPET HEIGHT (INCHES) FOR AGGREGATE SURFACED ROOFSa, b, c, d,
CBC § 1609.5 High relevance — show source text
Exposure C. Exposure C shall apply for all cases where Exposure B or D does not apply.

Exposure D. Exposure D shall apply where the ground surface roughness, as defined by Surface Roughness D, prevails in the upwind direction for a distance of not less than 5,000 feet (1524 m) or 20 times the height of the building, whichever is greater. Exposure D shall apply where the ground surface roughness immediately upwind of the site is B or C, and the site is within a distance of 600 feet (183 m) or 20 times the building height, whichever is greater, from an Exposure D condition as defined in the previous sentence.

1609.5 Tornado loads. The design and construction of Risk Category III and IV buildings and other structures located in the tornadoprone region as shown in Figure 1609.5 shall be in accordance with Chapter 32 of ASCE 7, except as modified by this code.

FIGURE 1609.5—TORNADO-PRONE REGION

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STRUCTURAL DESIGN

1609.6 Roof systems. Roof systems shall be designed and constructed in accordance with Sections 1609.6.1 through 1609.6.3, as applicable.

1609.6.1 Roof deck. The roof deck shall be designed to withstand the greater of wind pressures or tornado pressures determined in accordance with ASCE 7.

1609.6.2 Roof coverings. Roof coverings shall comply with Section 1609.6.1.

Exception: Rigid tile roof coverings that are air permeable and installed over a roof deck complying with Section 1609.6.1 are permitted to be designed in accordance with Section 1609.6.3.

1609.6.2.1 Asphalt shingles. Asphalt shingles installed over a roof deck complying with Section 1609.6.1 shall comply with the wind-resistance requirements of Section 1504.2.

1609.6.3 Rigid tile. Wind and tornado loads on rigid tiles shall comply with Section 1609.6.3.1 or 1609.6.3.2, as applicable.

1609.6.3.1 Aerodynamic uplift moment. The aerodynamic uplift moment for rigid tile roof coverings shall be determined in accordance with the following equation: Equation 16-19 M a = q h K d C L bLL a [1.0 - GC p ] For SI: M a = q h K d C L bLL a [1.0 - GC p ] / 1000

where:

b = Exposed width, feet (mm) of the roof tile.

C L = Lift coefficient. The lift coefficient for concrete and clay tile shall be 0.2 or shall be determined by test in accordance with Section 1504.3.1.

GC p = Roof pressure coefficient for each applicable roof zone determined from Chapter 30 of ASCE 7. Roof coefficients shall not be adjusted for internal pressure.

K d = Wind directionality factor determined from Chapter 26 of ASCE 7.
CBC § 6.1 High relevance — show source text
FIGURE 1609 A .5—TORNADO-PRONE REGION

1609 A .6 Roof systems. Roof systems shall be designed and constructed in accordance with Sections 1609 A .6.1 through 1609 A .6.3, as applicable.

1609 A .6.1 Roof deck. The roof deck shall be designed to withstand the greater of wind pressures or tornado pressures determined in accordance with ASCE 7.

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STRUCTURAL DESIGN

1609 A .6.2 Roof coverings. Roof coverings shall comply with Section 1609 A .6.1.

Exception: Rigid tile roof coverings that are air permeable and installed over a roof deck complying with Section 1609 A .6.1 are permitted to be designed in accordance with Section 1609 A .6.3.

1609 A .6.2.1 Asphalt shingles. Asphalt shingles installed over a roof deck complying with Section 1609 A .6.1 shall comply with the wind-resistance requirements of Section 1504.2.

1609 A .6.3 Rigid tile. Wind and tornado loads on rigid tiles shall comply with Section 1609 A .6.3.1 or 1609 A .6.3.2, as applicable.

1609 A .6.3.1 Aerodynamic uplift moment. The aerodynamic uplift moment for rigid tile roof coverings shall be determined in accordance with the following equation: Equation 16 A -19 M a = q h K d C L bLL a [1.0 - GC p ] For SI: M a = q h K d C L bLL a [1.0 - GC p ] / 1000

where:

b = Exposed width, feet (mm) of the roof tile.

C L = Lift coefficient. The lift coefficient for concrete and clay tile shall be 0.2 or shall be determined by test in accordance with Section 1504.3.1.

GC p = Roof pressure coefficient for each applicable roof zone determined from Chapter 30 of ASCE 7. Roof coefficients shall not be adjusted for internal pressure.

K d = Wind directionality factor determined from Chapter 26 of ASCE 7.

L = Length, feet (mm) of the roof tile.

L a = Moment arm, feet (mm) from the axis of rotation to the point of uplift on the roof tile. The point of uplift shall be taken at 0.76 L from the head of the tile and the middle of the exposed width.
CBC § 0.42 High relevance — show source text
Spacing of fasteners not included in this table shall be based on Table R602.3(2).
f. For wood structural panel roof sheathing attached to gable end roof framing and to intermediate supports within 48 inches of roof edges and ridges, nails shall be spaced at 4
inches on center where the ultimate design wind speed is greater than 130 mph in Exposure B or greater than 110 mph in Exposure C. Fastener spacing applies where roof
framing specific gravity is 0.42 or larger. Where roof framing specific gravity is greater than or equal to 0.35 but less than 0.42 in accordance with AWC NDS, fastening of roof
sheathing shall be with RSRS-03 (21/2″ × 0.131″ × 0.281″ head) nails.
g. Gypsum sheathing shall conform to ASTM C1396 and shall be installed in accordance with ASTM C1280 or GA 253 . Fiberboard sheathing shall conform to ASTM C208.
h. Spacing of fasteners on floor sheathing panel edges applies to panel edges supported by framing members and required blocking and at floor perimeters only. Spacing of fasteners
on roof sheathing panel edges applies to panel edges supported by framing members and required blocking. Blocking of roof or floor sheathing panel edges perpendicular to the
framing members need not be provided except as required by other provisions of this code. Floor perimeter shall be supported by framing members or solid blocking.
i. Where a rafter is fastened to an adjacent parallel ceiling joist in accordance with this schedule, provide two toe nails on one side of the rafter and toe nails from the ceiling joist
to top plate in accordance with this schedule. The toe nail on the opposite side of the rafter shall not be required.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s; 1 ksi = 6.895 MPa.
a. Nails are smooth-common, box or deformed shanks except where otherwise stated. Nails used for framing and sheathing connections are carbon steel and shall have mini-
mum average bending yield strengths as shown: 80 ksi for shank diameter of 0.192 inch (20d common nail), 90 ksi for shank diameters larger than 0.142 inch but not larger than
0.177 inch, and 100 ksi for shank diameters of 0.142 inch or less. Connections using nails and staples of other materials, such as stainless steel, shall be designed by accepted
engineering practice or approved under Section R104.2.2.
b. RSRS-01 is a Roof Sheathing Ring Shank nail meeting the specifications in ASTM F1667.
c. Nails shall be spaced at not more than 6 inches on center at all supports where spans are 48 inches or greater.
d. Four-foot by 8-foot or 4-foot by 9-foot panels shall be applied vertically.
e. Spacing of fasteners not included in this table shall be based on Table R602.3(2).
f. For wood structural panel roof sheathing attached to gable end roof framing and to intermediate supports within 48 inches of roof edges and ridges, nails shall be spaced at 4
inches on center where the ultimate design wind speed is greater than 130 mph in Exposure B or greater than 110 mph in Exposure C. Fastener spacing applies where roof
framing specific gravity is 0.42 or larger.
CBC § 2.1.1. High relevance — show source text
** Buildings and portions thereof shall be constructed in accordance with the wind provisions of this code using the ultimate design wind speed in Table R301.2 as determined from Figure R301.2(2). The structural provisions of this code for wind loads are not permitted where wind design is required as specified in Section R301.2.1.1. Where different construc-tion methods and structural materials are used for various portions of a building, the applicable requirements of this section for each portion shall apply. Where not otherwise specified, the wind loads listed in Table R301.2.1(1) adjusted for height and expo-sure using Table R301.2.1(2) shall be used to determine design load performance requirements for wall coverings, curtain walls, roof coverings, exterior windows, skylights, garage doors and exterior doors. Asphalt shingles shall be designed for wind speeds in accordance with Section R905.2.4. Metal roof shingles shall be designed for wind speeds in accordance with Section R905.4.4. A continuous load path shall be provided to transmit the applicable uplift forces in Section R802.11 from the roof assembly to the foundation. Where ultimate design wind speeds in Figure R301.2(2) are less than the lowest wind speed indicated in the prescrip-tive provisions of this code, the lowest wind speed indicated in the prescriptive provisions of this code shall be used.

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BUILDING PLANNING

0.2h

0.6h

FIGURE R301.2.1—COMPONENT AND CLADDING PRESSURE ZONES

3 0. Col3 Col4

2h
3
3 1'
0.6h
0.6h
0.6h
0
0.6h
3
3
2
2
2
1
1
2 1'
0.6h
0.6h
0.6h
0
0.6h
3
3
2
2
2
1
1
2

2h
3
3 1'
0.6h
0.6h
0.6h
0
0.6h
3
3
2
2
2
1
1
2 0.6h
0.6h
3
3 0.6h
0.6h
3
3

PLAN

Col1 Col2 Col3

Ѳ

Ѳ h

Gable and Flat Roofs Ѳ ≤ 7º

ELEVATION

h

Ѳ
B Col2 Col3

Ѳ
B B

ELEVATION VIEW

Col1 Col2 a a

2 3 3

1 2 2

2 3 3
CBC § 4.1 High relevance — show source text
1|||X||||||||||||||||||||| |R902.1 - R902.4|||X||||||||||||||||||||| |R903.4.1||||X|||||||||||||||||||| |R904.1 - R904.4|||X||||||||||||||||||||| |R905.15||||X|||||||||||||||||||| |R905.16||||X|||||||||||||||||||| |R907.1||||X|||||||||||||||||||| |R907.2 – R907.5|||X||||||||||||||||||||| |R909|||X|||||||||||||||||||||

The state agency does not adopt sections identified with the following symbol: †

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9 ROOF ASSEMBLIES

User notes:

About this chapter: Chapter 9 addresses the design and construction of roof assemblies. A roof assembly includes the roof deck, substrate or thermal barrier, insulation, vapor retarder and roof covering. This chapter provides the requirement for wind resistance of roof coverings. The types of roof covering materials and installation addressed by Chapter 9 are: asphalt shingles, clay and concrete tile, metal roof shingles, mineral-surfaced roll roofing, slate and slate-type shingles, wood shakes and shingles, built-up roofs, metal roof panels, modified bitumen roofing, thermoset and thermoplastic single-ply roofing, sprayed polyurethane foam roofing, liquid applied coatings and building-integrated photovoltaic (BIPV) roof coverings. Chapter 9 also provides requirements for roof drainage, flashing, above-deck thermal insulation, rooftop-mounted photovoltaic systems and recovering or replacing an existing roof covering.

SECTION R901—GENERAL

R901.1 Scope. The provisions of this chapter shall govern the design, materials, construction and quality of roof assemblies.

SECTION R902—FIRE CLASSIFICATION

R902.1 Roof assemblies. Roof decks shall be covered with materials as set forth in Section R904 or with roof coverings as set forth in Section R905. A minimum Class A, B or C roofing shall be installed in areas designated by this section or where the edge of the roof deck is less than 3 feet (914 mm) from a lot line. Where Class A, B or C roof assemblies are required, they shall be tested in accordance with ASTM E108 or UL 790. Where required, the roof assembly shall be listed and identified as to class by an approved testing agency.

Exceptions:
1. Class A roof assemblies include those with coverings of brick, masonry and exposed concrete roof deck.
2. Class A roof assemblies include ferrous or copper shingles or sheets, metal sheets and shingles, clay or concrete roof tile, or slate installed on noncombustible roof decks or ferrous, copper or metal sheets installed without a roof deck on noncombustible framing.
3. Class A roof assemblies include minimum 16 ounces per square foot (4.882 kg/m [2] ) copper sheets installed over combustible roof decks.
4. Class A roof assemblies include slate installed over underlayment over ASTM D226, Type II underlayment over combustible decks.
CBC § 1.18 High relevance — show source text
ASCE 7 Hazard Tool at https://asce7hazardtool.online/ or an approved equivalent. 2. Lines shown on the figure are contours separated by a constant ratio 1.18 with values of 10, 12, 14, 16, 19, 23, 27, 32, 38, 44, 52, 62, 73, 86, 101, 119 and 140 psf. 3. Values denoted with a “+” symbol indicate design ground snow loads at state capitals or other high-population locations. 4. Areas shown in gray represent areas with ground snow loads exceeding 140 psf. Ground snow load values for these locations can be determined from the Geodatabase. R301.2.1 Wind design criteria. Buildings and portions thereof shall be constructed in accordance with the wind provisions of this code using the ultimate design wind speed in Table R301.2 as determined from Figure R301.2(2). The structural provisions of this code for wind loads are not permitted where wind design is required as specified in Section R301.2.1.1. Where different construc-tion methods and structural materials are used for various portions of a building, the applicable requirements of this section for each portion shall apply. Where not otherwise specified, the wind loads listed in Table R301.2.1(1) adjusted for height and expo-sure using Table R301.2.1(2) shall be used to determine design load performance requirements for wall coverings, curtain walls, roof coverings, exterior windows, skylights, garage doors and exterior doors. Asphalt shingles shall be designed for wind speeds in accordance with Section R905.2.4. Metal roof shingles shall be designed for wind speeds in accordance with Section R905.4.4. A continuous load path shall be provided to transmit the applicable uplift forces in Section R802.11 from the roof assembly to the foundation. Where ultimate design wind speeds in Figure R301.2(2) are less than the lowest wind speed indicated in the prescrip-tive provisions of this code, the lowest wind speed indicated in the prescriptive provisions of this code shall be used.

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BUILDING PLANNING

0.2h

0.6h

FIGURE R301.2.1—COMPONENT AND CLADDING PRESSURE ZONES

CBC § 1507.1.1 High relevance — show source text

An approved
underlayment complying with Table 1507.1.1(1) for
the applicable roof covering and basic wind speed
shall be applied over the entire roof over the 4-inch-
wide membrane strips. Underlayment shall be
applied in accordance with this table using the
application requirements for where the maximum
basic wind speed is less than 130 mph.
3.
A single layer of self-adhering polymer modified
bitumen underlayment complying with ASTM
D1970, installed in accordance with the
underlayment and roof covering manufacturers’
installation instructions for the deck material, roof
ventilation configuration, and climate exposure of
the roof covering.| |For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s.|For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s.|

2025 CALIFORNIA BUILDING CODE 15-9

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

ROOF ASSEMBLIES AND ROOFTOP STRUCTURES

TABLE 1507.1.1(3)—UNDERLAYMENT FASTENING	Col2	Col3	Col4
ROOF COVERING	SECTION	MAXIMUM BASIC WIND SPEED,V < 130 MPH IN HURRICANE-PRONE REGIONS ORV < 140 MPH OUTSIDE HURRICANE-PRONE REGIONS	MAXIMUM BASIC WIND SPEED,V ≥ 130 MPH IN HURRICANE-PRONE REGIONS ORV ≥ 140 MPH OUTSIDE HURRICANE-PRONE REGIONS
Asphalt shingles	1507.2	Fastened sufficiently to hold in place	Mechanically fastened underlayment shall be fastened with corrosion-resistant fasteners in a grid pattern of not greater than 12 inches horizontally and vertically between side laps with a 6-inch spacing at side and end laps. Mechanically fastened underlayment shall be fastened using annular ring or deformed shank nails with 1-inch diameter metal or plastic caps. Metal caps shall have a thickness of not less than 32-gage (0.0134 inch) sheet metal. Power-driven metal caps shall have a minimum thickness of 0.010 inch. Minimum thickness of the outside edge of plastic caps shall be 0.035 inch. The cap nail shank shall be not less than 0.083 inch. The cap nail shank shall have a length sufficient to penetrate through the roof sheathing or not less than3/4 inch into the roof sheathing.

CBC § 1.0 High relevance — show source text

Interpolation shall be permitted for wind speed, mean roof height and parapet height. Extrapolation is not permitted.
c. Basic wind speed,V, and wind exposure shall be determined in accordance with Section 1609.
d. Where the minimum required parapet height is indicated to be 2 inches (51 mm), a gravel stop shall be permitted and shall extend not less than 2 inches (51 mm) from the roof
surface and not less than the height of the aggregate.
e. The tabulated values apply only to conditions where the topographic factor (Kzt) determined in accordance with Chapter 26 of ASCE 7 is 1.0 or where_Kzt_ is incorporated in the
basic wind speed in Section 1609.
f. For Exposure D, add 8 inches (203 mm) to the parapet height required for Exposure C and the parapet height shall not be less than 12 inches (305 mm).|

SECTION 1505—FIRE CLASSIFICATION

[BF] 1505.1 General. Fire classification of roof assemblies shall be in accordance with Section 1505. The minimum fire classification of roof assemblies installed on buildings shall comply with Table 1505.1 based on type of construction of the building. Class A, B and C roof assemblies and roof coverings required to be listed by this section shall be tested in accordance with ASTM E108 or UL 790. In addition, fire-retardant-treated woodroof coverings shall be tested in accordance with ASTM D2898; fire-retardant-treated shingles and shakes shall comply with Section 1505.6.

Exception: Skylights and sloped glazing that comply with Chapter 24 or Section 2610.

[BF] TABLE 1505.1—MINIMUM ROOF ASSEMBLY CLASSIFICATION FOR TYPES OF CONSTRUCTIONa, b	Col2	Col3	Col4	Col5	Col6	Col7	Col8	Col9
IA	IB	IIA	IIB	IIIA	IIIB	IV	VA	VB
B	B	B	Cc	B	Cc	B	B	Cc
For SI: 1 foot = 304.8 mm, 1 square foot = 0.0929 m2. a. Unless otherwise required in accordance with the_California Wildland-Urban Interface Code_ or due to the location of the building within a fire district in accordance with Appendix D. b. Nonclassified roof coverings shall be permitted on buildings of Group U occupancies, where there is a minimum fire-separation distance of 6 feet measured from the leading edge of the roof. c. Buildings that are not more than two stories above grade plane and having not more than 6,000 square feet of projected roof area and where there is a minimum 10-foot fire- separation distance from the leading edge of the roof to a lot line on all sides of the building, except for street fronts or public ways, shall be permitted to have roofs of No. 1 cedar or redwood shakes and No. 1 shingles constructed in accordance with Section 1505.7.	For SI: 1 foot = 304.8 mm, 1 square foot = 0.0929 m2. a. Unless otherwise required in accordance with the_California Wildland-Urban Interface Code_ or due to the location of the building within a fire district in accordance with Appendix D. b.

CBC § 15-8 High relevance — show source text

Underlayment shall be
applied in accordance with this table using the
application requirements for where the maximum
basic wind speed is less than 130 mph.
3.
A single layer of self-adhering polymer modified
bitumen underlayment complying with ASTM
D1970, installed in accordance with the
underlayment and roof covering manufacurers’
installation instructions for the deck material, roof
ventilation configuration, and climate exposure of
the roof covering.|

15-8 2025 CALIFORNIA BUILDING CODE

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

ROOF ASSEMBLIES AND ROOFTOP STRUCTURES

TABLE 1507.1.1(2)—UNDERLAYMENT APPLICATION—continued	Col2	Col3	Col4
ROOF COVERING	SECTION	MAXIMUM BASIC WIND SPEED,V < 130 MPH IN HURRICANE-PRONE REGIONS ORV < 140 MPH OUTSIDE HURRICANE-PRONE REGIONS	MAXIMUM BASIC WIND SPEED,V ≥ 130 MPH IN HURRICANE-PRONE REGIONS ORV ≥ 140 MPH OUTSIDE HURRICANE-PRONE REGIONS
Metal roof panels	1507.4	Apply in accordance with the manufacturer’s installa- tion instructions	Underlayment shall be one of the following: 1. Two layers of mechanically fastened underlayment applied in the following manner: Apply a strip of underlayment that is half the width of a full sheet parallel to and starting at the eaves, fastened sufficiently to hold in place. Starting at the eaves, apply full-width sheets of underlayment, overlapping successful sheets half the width of a full sheet plus 2 inches. Distortions in the underlayment shall not interfere with the ability of the shingles to seal. End laps shall be 4 inches and shall be offset by 6 feet. 2. A strip not less than 4 inches in width of self- adhering polymer modified bitumen underlayment complying with ASTM D1970, installed in accordance with the manufacturer’s installation instructions for the deck material, shall be applied over all joints in the roof decking. An approved underlayment complying with Table 1507.1.1(1) for the applicable roof covering and basic wind speed shall be applied over the entire roof over the 4-inch- wide membrane strips. Underlayment shall be applied in accordance with this table using the application requirements for where the maximum basic wind speed is less than 130 mph. 3. A single layer of self-adhering polymer modified bitumen underlayment complying with ASTM D1970, installed in accordance with the underlayment and roof covering manufacurers’ installation instructions for the deck material, roof ventilation configuration, and climate exposure of the roof covering.
Metal roof shingles	1507.5	1507.5	1507.

Frequently asked questions

Do I always need to get product labels showing ASTM tests?

Yes. § 1504.2 requires asphalt shingle packaging to bear a label indicating compliance with ASTM D7158 (or ASTM D3161 where allowed) and the required classification in Table 1504.2 .

Which wind speed value do I use when checking tables and tests?

Use the basic wind speed V determined from Figures 1609.3(1)–(4) (Section 1609); § 1504.6 explicitly requires that basic wind speed be used for ES‑1 edge testing and the code directs roof covering design to Chapter 16 wind values .

Are gutters tested the same as other edge flashings?

No. Gutters and counterflashing are excluded from the general metal edge testing in § 1504.6; gutters that secure the membrane must be designed per Section 1609 and tested per SPRI GT‑1 Test Methods G‑1 and G‑2 (§ 1504.6.1) .

What if my project uses a ballasted single‑ply roof?

Ballasted single‑ply low‑slope systems are designed per ANSI/SPRI RP‑4 as allowed by § 1504.5 (see related provisions) rather than the nonballasted test paths used for mechanically attached or adhered membranes .

If a shingle manufacturer gives a wind rating but no test standard on the label, is that acceptable?

No. The code requires the specific ASTM standard and classification to be shown on packaging for compliance with § 1504.2; a generic “wind‑rated” claim without a referenced test/class is not what the code requires .

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