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// CODE SNIPPET

R905.8 Wood Shakes

Residential Code 2015 of Utah > 9 Roof Assemblies > R905 REQUIREMENTS FOR ROOF COVERINGS > R905.8 Wood Shakes
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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 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.

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 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.

TABLE R905.8.5 WOOD SHAKE MATERIAL REQUIREMENTS

MATERIAL MINIMUM
GRADES
APPLICABLE
GRADING RULES
Wood shakes of naturally durable
wood
1 Cedar Shake and
Shingle Bureau
Tapersawn shakes of naturally
durable wood
1 or 2 Cedar Shake and
Shingle Bureau
Preservative-treated shakes and
shingles of naturally durable wood
1 Cedar Shake and
Shingle Bureau
Fire-retardant-treated shakes and
shingles of naturally durable wood
1 Cedar Shake and
Shingle Bureau
Preservative-treated tapersawn
shakes of Southern pine treated in
accordance with AWPA Standard
U1 (Commodity Specification A,
Use Category 3B and Section 5.6)
1 or 2 Forest Products
Laboratory of the
Texas Forest
Services

R905.8.6 Application

Wood shakes shall be installed in accordance with this chapter and the manufacturer's installation instructions. Wood shakes shall be laid with a side lap not less than 11/2 inches (38 mm) between joints in adjacent courses. Spacing between shakes in the same course shall be 3/8 inch to 5/8 inch (9.5 mm to 15.9 mm) including tapersawn shakes. Weather exposures for wood shakes shall not exceed those set in Table R905.8.6. Fasteners for untreated (naturally durable) wood shakes shall be box nails in accordance with Table R905.7.5(2). Nails shall be stainless steel Type 304, or Type 316 or hot-dipped with a coating weight of ASTM A153 Class D (1.0 oz/ft2). Alternatively, two 16-gage Type 304 or Type 316 stainless steel staples, with crown widths 7/16 inch (11.1 mm) minimum, 3/4 inch (19.1 mm) maximum, shall be used. Fasteners installed within 15 miles (24 km) of salt water coastal areas shall be stainless steel Type 316. Wood shakes shall be attached to the roof with two fasteners per shake positioned in accordance with the manufacturer's installation instructions Fasteners for fire-retardant-treated (as defined in Section R902) shakes or pressure-impregnated-preservative-treated shakes of naturally durable wood in accordance with AWPA U1 shall be stainless steel Type 316. All fasteners shall have a minimum penetration into the sheathing of 3/4 inch (19.1 mm). Where the sheathing is less than 3/4 inch (19.1 mm) thick, each fastener shall penetrate through the sheathing. Fastener packaging shall bear a label indicating the appropriate grade material or coating weight.

TABLE R905.8.6 WOOD SHAKE WEATHER EXPOSURE AND ROOF SLOPE

ROOFING MATERIAL LENGTH
(inches)
GRADE EXPOSURE (inches)
4:12 pitch or steeper
Shakes of naturally durable wood 18 No. 1 71/2
24 No. 1 10a
Preservative-treated tapersawn
shakes of Southern Yellow Pine
18 No. 1 71/2
24 No. 1 10
18 No. 2 51/2
24 No. 2 71/2
Taper-sawn shakes of naturally
durable wood
18 No. 1 71/2
24 No. 1 10
18 No. 2 51/2
24 No. 2 71/2

For SI: 1 inch = 25.4 mm.
a. For 24-inch by 3/8-inch handsplit shakes, the maximum exposure is 71/2 inches.

R905.8.7 Shake Placement

The starter course at the eaves shall be doubled and the bottom layer shall be either 15-inch (381 mm), 18-inch (457 mm) or 24-inch (610 mm) wood shakes or wood shingles. Fifteen-inch (381 mm) or 18-inch (457 mm) wood shakes shall be permitted to be used for the final course at the ridge. Shakes shall be interlaid with 18-inch-wide (457 mm) strips of not less than No. 30 felt shingled between each course in such a manner that no felt is exposed to the weather by positioning the lower edge of each felt strip above the butt end of the shake it covers a distance equal to twice the weather exposure.

R905.8.8 Valley Flashing

Roof valley flashing shall be not less than No. 26 gage [0.019 inch (0.5 mm)] corrosion-resistant sheet metal and shall extend not less than 11 inches (279 mm) from the centerline each way. Sections of flashing shall have an end lap of not less than 4 inches (102 mm).

R905.8.9 Label Required

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