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Underlayment for asphalt shingles, clay and concrete tile, metal roof shingles, mineral-surfaced roll roofing, slate and slate-type shingles, wood shingles, wood shakes, metal roof panels and photovoltaic shingles shall conform to the applicable standards listed in this chapter. Underlayment materials required to comply with ASTM D226, D1970, D4869 and D6757 shall bear a label indicating compliance with the standard designation and, if applicable, type classification indicated in Table 1507.1.1(1). Underlayment shall be applied in accordance with Table 1507.1.1(2). Underlayment shall be attached in accordance with Table 1507.1.1(3).
Exceptions:
  1. As an alternative, a minimum 4-inch-wide (102 mm) strip of self-adhering polymer modified bitumen membrane complying with ASTM D1970 and 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 for the applicable roof covering for design wind speeds less than 120 mph (54 m/s) shall be applied over the 4-inch-wide (102 mm) membrane strips.
  2.  As an alternative, two layers of underlayment complying with ASTM D226 Type II or ASTM D4869 Type IV shall be permitted to be installed as follows: Apply a 19-inch (483 mm) strip of underlayment parallel with the eave. Starting at the eave, apply 36-inch-wide (914 mm) strips of underlayment felt, overlapping successive sheets 19 inches (483 mm). The underlayment shall be attached with corrosion-resistant fasteners in a grid pattern of 12 inches (305 mm) between side laps with a 6-inch (152 mm) spacing at side and end laps. End laps shall be 4 inches (102 mm) and shall be offset by 6 feet (1829 mm). Underlayment shall be attached using metal or plastic cap nails with a nominal cap diameter of not less than 1 inch (25.4 mm). Metal caps shall have a thickness of not less than 32-gage sheet metal. Power-driven metal caps shall have a thickness of not less than 0.010 inch (0.254 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 (2.1 mm) for ring shank cap nails and 0.091 inch (2.3 mm) for smooth shank cap nails. The cap nail shank 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.
  3. Structural metal panels that do not require a substrate or underlayment.
ROOF COVERING SECTION MAXIMUM BASIC DESIGN WIND SPEED, V < 140 MPH MAXIMUM BASIC DESIGN WIND SPEED, V ≥ 140 MPH
Asphalt shingles 1507.2 ASTM D226 Type I or II

ASTM D4869 Type I, II, III or IV

ASTM D6757
ASTM D226 Type II

ASTM D4869 Type IV

ASTM D6757
Clay and concrete tiles 1507.3 ASTM D226 Type II

ASTM D2626 Type I

ASTM D6380 Class M mineral surfaced roll roofing
ASTM D226 Type II

ASTM D2626 Type I

ASTM D6380 Class M mineral surfaced roll roofing
Metal roof panels 1507.4 Manufacturer's instructions ASTM D226 Type II

ASTM D4869 Type IV
Metal roof shingles 1507.5 ASTM D226 Type I or II

ASTM D4869 Type I, II, III or IV
ASTM D226 Type II

ASTM D4869 Type IV
Mineral-surfaced roll roofing 1507.6 ASTM D226 Type I or II

ASTM D4869 Type I, II, III or IV
ASTM D226 Type II

ASTM D4869 Type IV
Slate shingles 1507.7 ASTM D226 Type II

ASTM D4869 Type III or IV
ASTM D226 Type II

ASTM D4869 Type IV
Wood shingles 1507.8 ASTM D226 Type I or II

ASTM D4869 Type I, II, III or IV
ASTM D226 Type II

ASTM D4869 Type IV
Wood shakes 1507.9 ASTM D226 Type I or II

ASTM D4869 Type I, II, III or IV
ASTM D226 Type II

ASTM D4869 Type IV
Photovoltaic shingles 1507.16 ASTM D226 Type I or II

ASTM D4869 Type I, II, III or IV

ASTM D6757
ASTM D226 Type II

ASTM D4869 Type IV

ASTM D6757
 
TABLE 1507.1.1(2)
UNDERLAYMENT APPLICATION
ROOF COVERING SECTION MAXIMUM BASIC DESIGN WIND SPEED, V < 140 MPH MAXIMUM BASIC DESIGN WIND SPEED, V ≥ 140 MPH
Asphalt shingles 1507.2 For roof slopes from 2 units vertical in 12 units horizontal (2:12), up to 4 units vertical in 12 units horizontal (4:12), underlayment shall be two layers applied as follows: Apply a 19-inch strip of underlayment felt parallel to and starting at the eaves. Starting at the eave, apply 36-inch-wide sheets of underlayment, overlapping successive sheets 19 inches. End laps shall be 4 inches and shall be offset by 6 feet. Distortions in the underlayment shall not interfere with the ability of the shingles to seal. For roof slopes of 4 units vertical in 12 units horizontal (4:12) or greater, underlayment shall be one layer applied as follows: Underlayment shall be applied shingle fashion, parallel to and starting from the eave and lapped 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. Same as Maximum Basic Design Wind Speed, V < 140 mph except all laps shall be not less than 4 inches
Clay and concrete tile 1507.3
For roof slopes from 21/2 units vertical in 12 units horizontal (21/2:12), up to 4 units vertical in 12 units horizontal (4:12), underlayment shall be not fewer than two layers applied as follows: Starting at the eave, a 19-inch strip of underlayment shall be applied parallel with the eave. Starting at the eave, a 36-inch-wide strip of underlayment felt shall be applied, overlapping successive sheets 19 inches. End laps shall be 4 inches and shall be offset by 6 feet.
For roof slopes of 4 units vertical in 12 units horizontal (4:12) or greater, underlayment shall be one layer applied as follows: Underlayment shall be applied shingle fashion, parallel to and starting from the eave and lapped 2 inches. End laps shall be 4 inches and shall be offset by 6 feet.
Same as Maximum Basic Design Wind Speed, V < 140 mph except all laps shall be not less than 4 inches
Metal roof panels 1507.4 Apply in accordance with the manufacturer's installation instructions For roof slopes from 2 units vertical in 12 units horizontal (2:12), up to 4 units vertical in 12 units horizontal (4:12), underlayment shall be two layers applied as follows: Apply a 19-inch strip of underlayment felt parallel to and starting at the eaves. Starting at the eave, apply 36-inch-wide sheets of underlayment, overlapping successive sheets 19 inches. End laps shall be 4 inches and shall be offset by 6 feet.

For roof slopes of 4 units vertical in 12 units horizontal (4:12) or greater, underlayment shall be one layer applied as follows: Underlayment shall be applied shingle fashion, parallel to and starting from the eave and lapped 4 inches. End laps shall be 4 inches and shall be offset by 6 feet.
Metal roof shingles 1507.5
Mineral-surfaced roll roofing 1507.6
Slate shingles 1507.7
Wood shingles 1507.8
Wood shakes 1507.9
Photovoltaic shingles 1507.16 For roof slopes from 3 units vertical in 12 units horizontal (3:12), up to 4 units vertical in 12 units horizontal (4:12), underlayment shall be two layers applied as follows: Apply a 19-inch strip of underlayment felt parallel to and starting at the eaves. Starting at the eave, apply 36-inch-wide sheets of underlayment, overlapping successive sheets 19 inches. End laps shall be 4 inches and shall be offset by 6 feet. Distortions in the underlayment shall not interfere with the ability of the shingles to seal.

For roof slopes of 4 units vertical in 12 units horizontal (4:12) or greater, underlayment shall be one layer applied as follows: Underlayment shall be applied shingle fashion, parallel to and starting from the eave and lapped 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.
Same as Maximum Basic Design Wind Speed, V < 140 mph except all laps shall be not less than 4 inches
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm; 1 mile per hour = 0.447 m/s.
 
TABLE 1507.1.1(3)
UNDERLAYMENT ATTACHMENT
ROOF COVERING SECTION MAXIMUM BASIC DESIGN WIND SPEED, V < 140 MPH MAXIMUM BASIC DESIGN WIND SPEED, V ≥ 140 MPH
Asphalt shingles 1507.2 Fastened sufficiently to hold in place The underlayment shall be attached with corrosion-resistant fasteners in a grid pattern of 12 inches between side laps with a 6-inch spacing at side and end laps. Underlayment shall be attached using metal or plastic cap nails or cap staples with a nominal cap diameter of not less than 1 inch. 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 for ring shank cap nails and 0.091 inch for smooth shank cap nails. Staples shall be not less than 21 gage (0.032 inch). The 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 into the roof sheathing.
Clay and concrete tile 1507.3
Photovoltaic shingles 1507.16
Metal roof panels 1507.4 Manufacturer's installation instructions The underlayment shall be attached with corrosion-resistant fasteners in a grid pattern of 12 inches between side laps with a 6-inch spacing at side and end laps. Underlayment shall be attached using metal or plastic cap nails or cap staples with a nominal cap diameter of not less than 1 inch. Metal caps shall have a thickness of not less than 32-gage 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 for ring shank cap nails and 0.091 inch for smooth shank cap nails. Staples shall be not less than 21 gage. The 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 into the roof sheathing.
Metal roof shingles 1507.5
Mineral-surfacedroll roofing 1507.6
Slate shingles 1507.7
Wood shingles 1507.8
Wood shakes 1507.9
For SI: 1 inch = 25.4 mm; 1 mile per hour = 0.447 m/s.

Related Code Sections

1507.1.1 Roof Assemblies and Rooftop Structures, Underlayment
Underlayment for asphalt shingles, clay and concrete tile, metal roof shingles, mineral-surfaced roll roofing, slate and slate-type shingles, wood ...
1507.1.1 Roof Assemblies and Rooftop Structures, Underlayment
Underlayment for asphalt shingles, clay and concrete tile, metal roof shingles, mineral-surfaced roll roofing, slate and slate-type shingles, wood ...
1507.3.3 Roof Assemblies and Rooftop Structures, Underlayment
Unless otherwise noted, required underlayment shall conform to: ASTM D226, Type II; ASTM D2626 or ASTM D6380, Class M mineral-surfaced roll roofing ...
1507.3.3 Roof Assemblies and Rooftop Structures, Underlayment
Unless otherwise noted, required underlayment shall conform to: ASTM D226, Type II; ASTM D2626 or ASTM D6380, Class M mineral-surfaced roll roofing ...