The installation of wood shakes shall comply with the provisions of this section.
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.
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.
Where required, ice barriers shall comply with Section R905.1.2.
Interlayment shall comply with ASTM D226, Type I.
Wood shakes shall comply with the requirements of Table R905.8.5.
TABLE R905.8.5 WOOD SHAKE MATERIAL REQUIREMENTS
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 |
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
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. |
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.