Weather protection, flashing, ventilation, and underlayment

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

• CBC § 1507.8.9 High relevance — show source text

  26 galvanized sheet gage) corrosion-resistant metal. The valley flashing shall extend not less than 11 inches (279 mm) from the centerline each way and have a splash diverter rib not less than 1 inch (25 mm) high at the flow line formed as part of the flashing. Sections of flashing shall have an end lap of not less than 4 inches (102 mm). For roof slopes of three units vertical in 12 units horizontal (25percent slope) and over, the valley flashing shall have a 36-inch-wide (914 mm) underlayment of either one layer of Type I underlayment running the full length of the valley or a self-adhering polymer-modified bitumen sheet bearing a label indicating compliance with ASTM D1970, in addition to other required underlayment. In areas where the average daily temperature in January is 25°F (-4°C) or less or where there is a possibility of ice forming along the eaves causing a backup of water, the metal valley flashing underlayment shall be solidly cemented to the roofing underlayment for slopes under seven units vertical in 12 units horizontal (58-percent slope) or self-adhering polymer-modified bitumen sheet shall be installed.

  1507.8.9 Label required. Each bundle of shingles shall be identified by a label of an approved grading or inspection bureau or

  agency.

  1507.9 Wood shakes. The installation of wood shakes shall comply with the provisions of this section and Table 1507.8.

  1507.9.1 Deck requirements. Wood shakes shall only be used on solid or spaced sheathing. Where spaced sheathing is used, sheathing boards shall be not less than 1-inch by 4-inch (25 mm by 102 mm) nominal dimensions and shall be spaced on centers equal to the weather exposure to coincide with the placement of fasteners. Where 1-inch by 4-inch (25 mm by 102 mm) spaced sheathing is installed at 10 inches (254 mm) on center, additional 1-inch by 4-inch (25 mm by 102 mm) boards shall be installed between the sheathing boards. Where wood shakes are installed over spaced sheathing and the underside of the shakes are exposed to the attic space, the attic shall be ventilated in accordance with Section 1202.2. The shakes shall not be backed with materials that will occupy the required air gap space and prevent the free movement of air on the interior side of the spaced sheathing.

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  ROOF ASSEMBLIES AND ROOFTOP STRUCTURES

  1507.9.1.1 Solid sheathing required. Solid sheathing is required in areas where the average daily temperature in January is 25°F (-4°C) or less or where there is a possibility of ice forming along the eaves causing a backup of water.

  1507.9.2 Deck slope. Wood shakes shall only be used on slopes of not less than 4 units vertical in 12 units horizontal (33-percent slope).

  1507.9.3 Underlayment. Underlayment shall comply with Section 1507.1.1.

  1507.9.4 Ice barrier. Where required, ice barriers shall comply with Section 1507.1.2.

  1507.9.5 Interlayment. Interlayment shall comply with ASTM D226, Type I.

• CBC § 1507.8.7 High relevance — show source text

  TABLE 1507.8.7—WOOD SHINGLE WEATHER EXPOSURE AND ROOF SLOPE	Col2	Col3	Col4	Col5
  ROOFING MATERIAL	LENGTH (inches)	GRADE	EXPOSURE (inches)	EXPOSURE (inches)
  ROOFING MATERIAL	LENGTH (inches)	GRADE	3:12 pitch to < 4:12	4:12 pitch or steeper
  Shingles of naturally durable wood	16	No. 1 No. 2 No. 3	3.75 3.5 3	5 4 3.5
  Shingles of naturally durable wood	18	No. 1 No. 2 No. 3	4.25 4 3.5	5.5 4.5 4
  Shingles of naturally durable wood	24	No. 1 No. 2 No. 3	5.75 5.5 5	7.5 6.5 5.5
  For SI: 1 inch = 25.4 mm.	For SI: 1 inch = 25.4 mm.	For SI: 1 inch = 25.4 mm.	For SI: 1 inch = 25.4 mm.	For SI: 1 inch = 25.4 mm.

  1507.8.8 Flashing. At the juncture of the roof and vertical surfaces, flashing and counterflashing shall be provided in accordance with the manufacturer’s installation instructions, and where of metal, shall be not less than 0.019-inch (0.48 mm) (No. 26 galvanized sheet gage) corrosion-resistant metal. The valley flashing shall extend not less than 11 inches (279 mm) from the centerline each way and have a splash diverter rib not less than 1 inch (25 mm) high at the flow line formed as part of the flashing. Sections of flashing shall have an end lap of not less than 4 inches (102 mm). For roof slopes of three units vertical in 12 units horizontal (25percent slope) and over, the valley flashing shall have a 36-inch-wide (914 mm) underlayment of either one layer of Type I underlayment running the full length of the valley or a self-adhering polymer-modified bitumen sheet bearing a label indicating compliance with ASTM D1970, in addition to other required underlayment. In areas where the average daily temperature in January is 25°F (-4°C) or less or where there is a possibility of ice forming along the eaves causing a backup of water, the metal valley flashing underlayment shall be solidly cemented to the roofing underlayment for slopes under seven units vertical in 12 units horizontal (58-percent slope) or self-adhering polymer-modified bitumen sheet shall be installed.

  1507.8.9 Label required. Each bundle of shingles shall be identified by a label of an approved grading or inspection bureau or

  agency.

  1507.9 Wood shakes. The installation of wood shakes shall comply with the provisions of this section and Table 1507.8.

  1507.9.1 Deck requirements. Wood shakes shall only be used on solid or spaced sheathing.

• CBC § 5.5 High relevance — show source text

  2|5.5
  7.5| |Taper sawn shakes of naturally durable wood|18
  24|No. 1
  No. 1|7.5
  10| |Taper sawn shakes of naturally durable wood|18
  24|No. 2
  No. 2|5.5
  7.5| |For SI: 1 inch = 25.4 mm.
  a. For 24-inch by 0.375-inch handsplit shakes, the maximum exposure is 7.5 inches.|For SI: 1 inch = 25.4 mm.
  a. For 24-inch by 0.375-inch handsplit shakes, the maximum exposure is 7.5 inches.|For SI: 1 inch = 25.4 mm.
  a. For 24-inch by 0.375-inch handsplit shakes, the maximum exposure is 7.5 inches.|For SI: 1 inch = 25.4 mm.
  a. For 24-inch by 0.375-inch handsplit shakes, the maximum exposure is 7.5 inches.|

  1507.9.9 Flashing. At the juncture of the roof and vertical surfaces, flashing and counterflashing shall be provided in accordance with the manufacturer’s installation instructions, and where of metal, shall be not less than 0.019-inch (0.48 mm) (No. 26 galvanized sheet gage) corrosion-resistant metal. The valley flashing shall extend not less than 11 inches (279 mm) from the centerline each way and have a splash diverter rib not less than 1 inch (25 mm) high at the flow line formed as part of the flashing. Sections of flashing shall have an end lap of not less than 4 inches (102 mm). For roof slopes of three units vertical in 12 units horizontal (25percent slope) and over, the valley flashing shall have a 36-inch-wide (914 mm) underlayment of either one layer of Type I underlayment running the full length of the valley or a self-adhering polymer-modified bitumen sheet bearing a label indicating compliance with ASTM D1970, in addition to other required underlayment. In areas where the average daily temperature in January is 25°F (-4°C) or less or where there is a possibility of ice forming along the eaves causing a backup of water, the metal valley flashing underlayment shall be solidly cemented to the roofing underlayment for slopes under seven units vertical in 12 units horizontal (58-percent slope) or self-adhering polymer-modified bitumen sheet shall be installed.

  2025 CALIFORNIA BUILDING CODE 15-17

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

  ROOF ASSEMBLIES AND ROOFTOP STRUCTURES

  1507.9.10 Label required. Each bundle of shakes shall be identified by a label of an approved grading or inspection bureau or

  agency.

  1507.10 Built-up roofs. The installation of built-up roofs shall comply with the provisions of this section. 1507.10.1 Slope. Built-up roofs shall have a design slope of not less than [1] / 4 unit vertical in 12 units horizontal (2-percent slope) for drainage, except for coal-tar built-up roofs that shall have a design slope of not less than [1] / 8 unit vertical in 12 units horizontal (1-percent slope).

• CBC § 0.083 High relevance — show source text

  Minimum fastener size. Corrosion-resistant nails not less than No. 11 gage with5/16-inch head. Fasteners shall be long enough to penetrate into the sheathing3/4 inch or
  through the thickness of the sheathing, whichever is less. Attaching wire for clay and concrete tile shall not be smaller than 0.083 inch.
  b. Snow areas. Not fewer than two fasteners per tile are required or battens and one fastener.
  c. Roof slopes greater than 24:12. The nose of all tiles shall be securely fastened.
  d. Horizontal battens. Battens shall be not less than 1 inch by 2 inches nominal. Provisions shall be made for drainage by a riser of not less than1/8 inch at each nail or by 4-foot-
  long battens with not less than a1/2-inch separation between battens. Horizontal battens are required for slopes over 7:12.
  e. Perimeter fastening areas include three tile courses but not less than 36 inches from either side of hips or ridges and edges of eaves and_gable_ rakes.
  f._ Vasd_ shall be determined in accordance with Section 1609.3.1.|

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  ROOF ASSEMBLIES AND ROOFTOP STRUCTURES

  1507.3.8 Application. Tile shall be applied according to the manufacturer’s installation instructions, based on the following:

  1. Climatic conditions.

  2. Roof slope.

  3. Underlayment system.

  4. Type of tile being installed.

  1507.3.9 Flashing. At the juncture of the roof vertical surfaces, flashing and counterflashing shall be provided in accordance with the manufacturer’s installation instructions, and where of metal, shall be not less than 0.019-inch (0.48 mm) (No. 26 galvanized sheet gage) corrosion-resistant metal. The valley flashing shall extend not less than 11 inches (279 mm) from the centerline each way and have a splash diverter rib not less than 1 inch (25 mm) high at the flow line formed as part of the flashing. Sections of flashing shall have an end lap of not less than 4 inches (102 mm). For roof slopes of three units vertical in 12 units horizontal (25-percent slope) and over, the valley flashing shall have a 36-inch-wide (914 mm) underlayment of either one layer of Type I underlayment running the full length of the valley, or a self-adhering polymer-modified bitumen sheet bearing a label indicating compliance with ASTM D1970, in addition to other required underlayment. In areas where the average daily temperature in January is 25°F (-4°C) or less or where there is a possibility of ice forming along the eaves causing a backup of water, the metal valley flashing underlayment shall be solid cemented to the roofing underlayment for slopes under seven units vertical in 12 units horizontal (58-percent slope) or self-adhering polymer-modified bitumen sheet shall be installed.

• CBC § 1507.16.9 High relevance — show source text

  1507.16.9 Flashing. Flashing for BIPV shingles shall be installed in accordance with the roof covering manufacturer’s installation instructions 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.

  1507.17 Building-integrated photovoltaic roof panels. The installation of BIPV roof panels shall comply with the provisions of this section.

  1507.17.1 Deck requirements. BIPV roof panels shall be applied to a solid or closely fitted deck, except where the roof covering is specifically designed to be applied over spaced sheathing.

  1507.17.2 Deck slope. BIPV roof panels shall be used only on roof slopes of 2 units vertical in 12 units horizontal (2:12) or greater.

  1507.17.3 Underlayment. Underlayment shall comply with ASTM D226, ASTM D4869 or ASTM D6757.

  2025 CALIFORNIA BUILDING CODE 15-19

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  ROOF ASSEMBLIES AND ROOFTOP STRUCTURES

  1507.17.4 Underlayment application. Underlayment shall be applied shingle fashion, parallel to and starting from the eave, lapped 2 inches (51 mm) and fastened sufficiently to hold in place.

  1507.17.4.1 High-wind attachment. Underlayment applied in areas subject to high winds [V asd greater than 110 mph (49 m/s) as determined in accordance with Section 1609.3.1] shall be applied in accordance with the manufacturer’s instructions. Fasteners shall be applied along the overlap at not more than 36 inches (914 mm) on center. Underlayment installed where V asd is not less than 120 mph (54 m/s) shall comply with ASTM D226, Type III, ASTM D4869, Type IV or ASTM D6757. The underlayment shall be attached in a grid pattern of 12 inches (305 mm) between side laps with a 6-inch (152 mm) spacing at the side laps. The underlayment shall be applied in accordance with Section 1507.1.1 except all laps shall be not less than 4 inches (102 mm). Underlayment shall be attached using cap nails or cap staples. Caps shall be metal or plastic with a nominal head diameter of not less than 1 inch (25.4 mm). Metal caps shall have a thickness of not less than 0.010 inch (0.25 mm). Power-driven metal caps shall have a thickness of not less than 0.010 inch (0.25 mm). Thickness of the outside edge of plastic caps shall be not less than 0.035 inch (0.89 mm). The cap nail shank shall be not less than 0.083 inch (2.11 mm) for ring shank cap nails and 0.091 inch (2.31 mm) for smooth shank cap nails. Staple gage shall be not less than 21 gage [0.0.2 inch (0.81 mm)]. Cap nail shank and cap staple legs shall have a length sufficient to penetrate through-the-roof sheathing or not less than [3] / 4 inch (19.1 mm) into the roof sheathing.

  Exception: As an alternative, adhered underlayment complying with ASTM D1970 shall be permitted.

• CBC § 1507.6 High relevance — show source text

  The metal valley flashing underlayment shall be solidly cemented to the roofing underlayment for roof slopes under seven units vertical in 12 units horizontal (58-percent slope) or selfadhering polymer-modified bitumen sheet shall be installed.

  1507.6 Mineral-surfaced roll roofing. The installation of mineral-surfaced roll roofing shall comply with this section.

  1507.6.1 Deck requirements. Mineral-surfaced roll roofing shall be fastened to solidly sheathed roofs.

  1507.6.2 Deck slope. Mineral-surfaced roll roofing shall not be applied on roof slopes below 1 unit vertical in 12 units horizontal (8-percent slope).

  1507.6.3 Underlayment. Underlayment shall comply with Section 1507.1.1.

  1507.6.4 Ice barrier. Where required, ice barriers shall comply with Section 1507.1.2.

  1507.6.5 Material standards. Mineral-surfaced roll roofing shall conform to ASTM D3909 or ASTM D6380.

  1507.7 Slate shingles. The installation of slate shingles shall comply with the provisions of this section.

  1507.7.1 Deck requirements. Slate shingles shall be fastened to solidly sheathed roofs.

  1507.7.2 Deck slope. Slate shingles shall only be used on slopes of 4 units vertical in 12 units horizontal (4:12) or greater.

  1507.7.3 Underlayment. Underlayment shall comply with Section 1507.1.1.

  1507.7.4 Ice barrier. Where required, ice barriers shall comply with Section 1507.1.2.

  1507.7.5 Material standards. Slate shingles shall comply with ASTM C406.

  1507.7.6 Application. Minimum headlap for slate shingles shall be in accordance with Table 1507.7.6. Slate shingles shall be secured to the roof with two fasteners per slate.

  TABLE 1507.7.6—SLATE SHINGLE HEADLAP	Col2
  SLOPE	HEADLAP (inches)
  4:12 < slope < 8:12	4
  8:12 < slope < 20:12	3
  slope ≥ 20:12	2
  For SI: 1 inch = 25.4 mm.	For SI: 1 inch = 25.4 mm.

  1507.7.7 Flashing. Flashing and counterflashing shall be made with sheet metal. Valley flashing shall be not less than 15 inches (381 mm) wide. Valley and flashing metal shall be a minimum uncoated thickness of 0.0179-inch (0.455 mm) zinc-coated G90. Chimneys, stucco or brick walls shall have not fewer than two plies of felt for a cap flashing consisting of a 4-inch-wide (102 mm)

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  ROOF ASSEMBLIES AND ROOFTOP STRUCTURES

  strip of felt set in plastic cement and extending 1 inch (25 mm) above the first felt and a top coating of plastic cement. The felt shall extend over the base flashing 2 inches (51 mm).

• CBC § 6.7 High relevance — show source text

  R905.6.7 Flashing. Flashing and counterflashing shall be made with sheet metal. Valley flashing shall be not less than 15 inches (381 mm) wide. Valley and flashing metal shall be a minimum uncoated thickness of 0.0179-inch (0.5 mm) zinc-coated G90. Chimneys, stucco or brick walls shall have not less than two plies of felt for a cap flashing consisting of a 4-inch-wide (102 mm) strip of felt set in plastic cement and extending 1 inch (25 mm) above the first felt and a top coating of plastic cement. The felt shall extend 2 inches (51 mm) over the base flashing.

  R905.7 Wood shingles. The installation of wood shingles shall comply with the provisions of this section.

  R905.7.1 Sheathing requirements. Wood shingles shall be fastened to wood structural panels, solid lumber sheathing or spaced lumber sheathing. Where spaced lumber sheathing is used, sheathing boards shall be not less than 1-inch by 4-inch (25 mm by 102 mm) nominal dimensions and shall be spaced on centers equal to the weather exposure to coincide with the placement of fasteners. Where 1-inch by 4-inch (25 mm by 102 mm) spaced sheathing is installed at 10 inches (254 mm) or greater, additional 1-inch by 4-inch (25 mm by 102 mm) boards shall be installed between the sheathing boards. Where wood shingles are installed over spaced sheathing and the underside of the shingles are exposed to the attic space, the attic shall be ventilated in accordance with Sections R806.1, R806.2, R806.3 and R806.4. The shingles shall not be backed with materials that will occupy the required air gap space and prevent the free movement of air on the interior side of the spaced sheathing.

  R905.7.1.1 Solid sheathing required. In areas where the average daily temperature in January is 25°F (-4°C) or less, wood structural panels or solid lumber sheathing is required on that portion of the roof deck requiring the application of an ice barrier.

  R905.7.2 Slope. Wood shingles shall be installed on slopes of 3 units vertical in 12 units horizontal (25-percent slope) or greater.

  R905.7.3 Underlayment. Underlayment shall comply with Section R905.1.1.

  R905.7.3.1 Ice barrier. Where required, ice barriers shall comply with Section R905.1.2.

  R905.7.4 Material standards. Wood shingles shall be of naturally durable wood and comply with the requirements of Table R905.7.4.

  TABLE R905.7.4—WOOD SHINGLE MATERIAL REQUIREMENTS	Col2	Col3
  ** MATERIAL**	** MINIMUM GRADES**	** APPLICABLE GRADING RULES**
  Wood shingles of naturally durable wood	1, 2 or 3	CSSB

• CBC § 7.7 High relevance — show source text

  R905.7.7 Valley flashing. Roof flashing shall be not less than No. 26 gage [0.019 inches (0.5 mm)] corrosion-resistant sheet metal and shall extend 10 inches (254 mm) from the centerline each way for roofs having slopes less than 12 units vertical in 12 units horizontal (100-percent slope), and 7 inches (178 mm) from the centerline each way for slopes of 12 units vertical in 12 units horizontal (100-percent slope) and greater. Sections of flashing shall have an end lap of not less than 4 inches (102 mm).

  R905.7.8 Label required. Each bundle of shingles shall be identified by a label of an approved grading or inspection bureau or

  agency.

  R905.8 Wood shakes. The installation of wood shakes shall comply with the provisions of this section.

  R905.8.1 Sheathing requirements. Wood shakes shall be fastened to wood structural panels, solid lumber sheathing or spaced lumber sheathing. Where spaced lumber sheathing is used, sheathing boards shall be not less than 1-inch by 4-inch (25 mm by 102 mm) nominal dimensions and shall be spaced on centers equal to the weather exposure to coincide with the placement of fasteners. Where 1-inch by 4-inch (25 mm by 102 mm) spaced lumber sheathing is installed at 10 inches (254 mm) on center, additional 1-inch by 4-inch (25 mm by 102 mm) boards shall be installed between the sheathing boards. Where wood shakes are installed over spaced sheathing and the underside of the shakes are exposed to the attic space, the attic shall be ventilated in accordance with Sections R806.1, R806.2, R806.3 and R806.4. The shakes shall not be backed with materials that will occupy the required air gap space and prevent the free movement of air on the interior side of the spaced sheathing.

  R905.8.1.1 Solid sheathing required. In areas where the average daily temperature in January is 25°F (-4°C) or less, wood structural panels or solid lumber sheathing is required on that portion of the roof deck requiring an ice barrier.

  R905.8.2 Slope. Wood shakes shall only be used on slopes of 3 units vertical in 12 units horizontal (25-percent slope) or greater.

  R905.8.3 Underlayment. Underlayment shall comply with Section R905.1.1.

  R905.8.3.1 Ice barrier. Where required, ice barriers shall comply with Section R905.1.2.

  R905.8.4 Interlayment. Interlayment shall comply with ASTM D226, Type I.

  R905.8.5 Material standards. Wood shakes shall comply with the requirements of Table R905.8.5.

  2025 CALIFORNIA RESIDENTIAL CODE 9-13

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

  ROOF ASSEMBLIES

• CBC § 4.1 High relevance — show source text

  For roof slopes of 3 units vertical in 12 units horizontal (25-percent slope) and greater, valley flashing shall have a 36-inch-wide (914 mm) underlayment of one layer of Type I underlayment running the full length of the valley, in addition to other required underlayment. In areas where the average daily temperature in January is 25°F (-4°C) or less, metal valley flashing underlayment shall be solid-cemented to the roofing underlayment for slopes less than 7 units vertical in 12 units horizontal (58-percent slope) or be of self-adhering polymer-modified bitumen sheet.

  R905.4 Metal roof shingles. The installation of metal roof shingles shall comply with the provisions of this section.

  R905.4.1 Sheathing requirements. Metal roof shingles shall be fastened to wood structural panels, solid lumber sheathing or closely fitted lumber sheathing, except where the roof covering is specifically designed to be applied to spaced lumber sheathing.

  R905.4.2 Slope. Metal roof shingles shall not be installed on roof slopes below 3 units vertical in 12 units horizontal (25-percent slope).

  R905.4.3 Underlayment. Underlayment shall comply with Section R905.1.1.

  R905.4.3.1 Ice barrier. Where required, ice barriers shall comply with Section R905.1.2.

  R905.4.4 Material standards. Metal roof shingle roof coverings shall comply with Table R905.10.3(1). The materials used for metal roof shingle roof coverings shall be naturally corrosion resistant or be made corrosion resistant in accordance with the standards and minimum thicknesses listed in Table R905.10.3(2).

  R905.4.4.1 Wind resistance of metal roof shingles. Metal roof shingles fastened to wood structural panels, solid lumber sheathing or closely fitted lumber sheathing 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 R905.4.4.1 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 R905.2.4.1.

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  ROOF ASSEMBLIES

• CBC § 1507.1.1. Medium relevance — show source text

  Where 1″ × 4″ spaced sheathing is
  installed at 10 inches, boards must be installed
  between the sheathing boards.| |In areas where the average daily
  temperature in January is 25°F or
  less or where there is a possibility
  of ice forming along the eaves
  causing a backup of water.|Solid sheathing is required.|Solid sheathing is required.| |3. Interlayment|No requirements.|Interlayment shall comply with ASTM D226, Type 1.| |4. Underlayment|4. Underlayment|4. Underlayment| |Temperate climate|Underlayment shall comply with Section
  1507.1.1.|Underlayment shall comply with Section 1507.1.1.| |5. Application|5. Application|5. Application| |Attachment|Fasteners for wood shingles shall be hot-
  dipped galvanized or Type 304 (Type 316 for
  coastal areas) stainless steel with a minimum
  penetration of 0.75 inch into the sheathing.
  For sheathing less than 0.5 inch thick, the
  fasteners shall extend through the sheathing.|Fasteners for wood shakes shall be hot-dipped galva-
  nized or Type 304 (Type 316 for coastal areas) with a
  minimum penetration of 0.75 inch into the sheath-
  ing. For sheathing less than 0.5 inch thick, the
  fasteners shall extend through the sheathing.| |No. of fasteners|Two per shingle.|Two per shake.| |Exposure|Weather exposures shall not exceed those set
  forth in Table 1507.8.7.|Weather exposures shall not exceed those set forth in
  Table 1507.9.8.| |Method|Shingles shall be laid with a side lap of not
  less than 1.5 inches between joints in courses,
  and no two joints in any three adjacent
  courses shall be in direct alignment. Spacing
  between shingles shall be 0.25 to 0.375 inch.|Shakes shall be laid with a side lap of not less than
  1.5 inches between joints in adjacent courses. Spac-
  ing between shakes shall not be less than 0.375 inch
  or more than 0.625 inch for shakes and taper sawn
  shakes of naturally durable wood and shall be 0.25 to
  0.375 inch for preservative-treated taper sawn
  shakes.| |Flashing|In accordance with Section 1507.8.8.|In accordance with Section 1507.9.9.| |For SI: 1 inch = 25.4 mm, °C = [(°F) - 32]/1.8.|For SI: 1 inch = 25.4 mm, °C = [(°F) - 32]/1.8.|For SI: 1 inch = 25.4 mm, °C = [(°F) - 32]/1.8.|

  1507.8.1 Deck requirements. Wood shingles shall be installed on solid or spaced sheathing. Where spaced sheathing is used, sheathing boards shall be not less than 1-inch by 4-inch (25 mm by 102 mm) nominal dimensions and shall be spaced on centers equal to the weather exposure to coincide with the placement of fasteners.

• CBC § 4.5 Medium relevance — show source text

  R905.4.5 Application. Metal roof shingles shall be secured to the roof in accordance with this chapter and the approved manufacturer’s installation instructions.

  R905.4.6 Flashing. Roof valley flashing shall be of corrosion-resistant metal of the same material as the roof covering or shall comply with the standards in Table R905.10.3(1). The valley flashing shall extend not less than 8 inches (203 mm) from the centerline each way and shall have a splash diverter rib not less than [3] / 4 inch (19 mm) in height at the flow line formed as part of the flashing. Sections of flashing shall have an end lap of not less than 4 inches (102 mm). The metal valley flashing shall have a 36inch-wide (914 mm) underlayment directly under it consisting of one layer of underlayment running the full length of the valley, in addition to underlayment required for metal roof shingles. In areas where the average daily temperature in January is 25°F (-4°C) or less, the metal valley flashing underlayment shall be solid-cemented to the roofing underlayment for roof slopes under 7 units vertical in 12 units horizontal (58-percent slope) or self-adhering polymer-modified bitumen sheet.

  R905.5 Mineral-surfaced roll roofing. The installation of mineral-surfaced roll roofing shall comply with this section.

  R905.5.1 Sheathing requirements. Mineral-surfaced roll roofing shall be fastened to wood structural panels or solid lumber sheathing.

  R905.5.2 Slope. Mineral-surfaced roll roofing shall not be applied on roof slopes below 1 unit vertical in 12 units horizontal (8percent slope).

  R905.5.3 Underlayment. Underlayment shall comply with Section R905.1.1.

  R905.5.3.1 Ice barrier. Where required, ice barriers shall comply with Section R905.1.2.

  R905.5.4 Material standards. Mineral-surfaced roll roofing shall conform to ASTM D3909 or ASTM D6380, Class M.

  R905.5.5 Application. Mineral-surfaced roll roofing shall be installed in accordance with this chapter and the manufacturer’s instructions.

  R905.5.6 Wind resistance of mineral-surfaced roll roofing. Mineral-surfaced roll roofing 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).

  R905.6 Slate shingles. The installation of slate shingles shall comply with the provisions of this section.

  R905.6.1 Sheathing requirements. Slate shingles shall be fastened to wood structural panels or solid lumber sheathing.

  R905.6.2 Slope. Slate shingles shall be used only on slopes of 4 units vertical in 12 units horizontal (33-percent slope) or greater.

  R905.6.3 Underlayment. Underlayment shall comply with Section R905.1.1.

  R905.6.3.1 Ice barrier. Where required, ice barriers shall comply with Section R905.1.2.

  R905.6.4 Material standards. Slate shingles shall comply with ASTM C406.

• CBC § 3.8. Medium relevance — show source text

  In other areas, clay and concrete roof tiles shall be attached in accordance with Table R905.3.8.

  TABLE R905.3.8—CLAY AND CONCRETE TILE ATTACHMENT	Col2	Col3
  ** SHEATHING**	** ROOF SLOPE**	** NUMBER OF FASTENERS**
  Solid without battens	All	One per tile
  Spaced or solid with battens	Slope < 5:12	Fasteners not required
  Spaced sheathing without battens	5:12 ≤ slope < 12:12	One per tile/every other row
  Spaced sheathing without battens	12:12 ≤ slope < 24:12	One per tile

  R905.3.9 Flashing. At the juncture of roof vertical surfaces, flashing and counterflashing shall be provided in accordance with this chapter and the manufacturer’s installation instructions and, where of metal, shall be not less than 0.019 inch (0.5 mm) (No. 26 galvanized sheet gage) corrosion-resistant metal. The valley flashing shall extend not less than 11 inches (279 mm) from the centerline each way and have a splash diverter rib not less than 1 inch (25 mm) in height at the flow line formed as part of the flashing. Sections of flashing shall have an end lap of not less than 4 inches (102 mm). For roof slopes of 3 units vertical in 12 units horizontal (25-percent slope) and greater, valley flashing shall have a 36-inch-wide (914 mm) underlayment of one layer of Type I underlayment running the full length of the valley, in addition to other required underlayment. In areas where the average daily temperature in January is 25°F (-4°C) or less, metal valley flashing underlayment shall be solid-cemented to the roofing underlayment for slopes less than 7 units vertical in 12 units horizontal (58-percent slope) or be of self-adhering polymer-modified bitumen sheet.

  R905.4 Metal roof shingles. The installation of metal roof shingles shall comply with the provisions of this section.

  R905.4.1 Sheathing requirements. Metal roof shingles shall be fastened to wood structural panels, solid lumber sheathing or closely fitted lumber sheathing, except where the roof covering is specifically designed to be applied to spaced lumber sheathing.

  R905.4.2 Slope. Metal roof shingles shall not be installed on roof slopes below 3 units vertical in 12 units horizontal (25-percent slope).

  R905.4.3 Underlayment. Underlayment shall comply with Section R905.1.1.

  R905.4.3.1 Ice barrier. Where required, ice barriers shall comply with Section R905.1.2.

  R905.4.4 Material standards. Metal roof shingle roof coverings shall comply with Table R905.10.3(1). The materials used for metal roof shingle roof coverings shall be naturally corrosion resistant or be made corrosion resistant in accordance with the standards and minimum thicknesses listed in Table R905.10.3(2).