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 and
greater. Sections of flashing shall have an end lap of not less than 4 inches (102 mm).
R905.7.7 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 Deck Requirements
Wood shakes shall be used only on solid or spaced sheathing. Where spaced sheathing is used, sheathing boards shall not be
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.
R905.8.1.1 Solid Sheathing Required
In areas where the average daily temperature in January is 25°F (-4°C) or less, solid sheathing is required on that portion of
the roof requiring an ice barrier.
R905.8.2 Deck Slope
Wood shakes shall only be used on slopes of three units vertical in 12 units horizontal (25-percent slope) or greater.
R905.8.3 Underlayment
Underlayment shall comply with ASTM D 226, Type I or ASTM D 4869, Type I or II.
R905.8.3.1 Ice Barrier
In areas where there has been a history of ice forming along the eaves causing a backup of water as designated in Table
R301.2(1), an ice barrier that consists of at least two layers of underlayment cemented together or a self-adhering polymer
modified bitumen sheet shall be used in place of normal underlayment and extend from the lowest edges of all roof surfaces
to a point at least 24 inches (610 mm) inside the exterior wall line of the building.
Exception: Detached accessory structures that contain no conditioned floor area.
R905.8.3.2 Underlayment and High Winds
Underlayment applied in areas subject to high winds [above 110 mph (49 m/s) in accordance with Figure R301.2(4)A] shall
be applied with corrosion-resistant fasteners in accordance with manufacturer's installation instructions. Fasteners are to be
applied along the overlap not farther apart than 36 inches (914 mm) on center.
Underlayment installed where the basic wind speed equals or exceeds 120 mph (54 m/s) shall comply with ASTM D 226
Type II or ASTM D 4869 Type IV. 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. Underlayment shall be applied in accordance with Section R905.2.7
except all laps shall be a minimum of 4 inches (102 mm). Underlayment shall be attached using metal or plastic cap nails
with a head diameter of not less than 1 inch (25.4 mm) with a thickness of at least 32-gauge sheet metal. The cap-nail shank
shall be a minimum of 12 gauge (0.105 inches) with a length to penetrate through the roof sheathing or a minimum of
3
/
4
inch
(19 mm) into the roof sheathing.
