Code of Massachusetts Regulations
780 CMR - STATE BOARD OF BUILDING REGULATIONS AND STANDARDS
Chapter 15 - Roof Assemblies and Rooftop Structures
Section 1507 - REQUIREMENTS FOR ROOF COVERINGS
Subsection 1507.9 - Wood shakes
Current through Register 1531, September 27, 2024
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 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) o.c., additional 1-inch by 4-inch (25 mm by 102 mm) boards shall be installed between the sheathing boards.
1507.9.2 Deck slope. Wood shakes shall only be used on slopes of four units vertical in 12 units horizontal (33-percent slope) or greater.
1507.9.3 Underlayment. Underlayment shall comply with ASTM D 226, Type I or ASTM D 4869.
1507.9.4 Ice barrier. In areas where there has been a history of ice forming along the eaves causing a backup of water, an ice barrier that consists of at least two layers of underlayment cemented together or of a self-adhering polymer-modified bitumen sheet shall be used in lieu 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.
1507.9.5 Interlayment. Interlayment shall comply with ASTM D 226, Type I.
1507.9.6 Material standards. Wood shakes shall comply with the requirements of Table 1507.9.6.
TABLE 1507.9.6 WOOD SHAKE MATERIAL REQUIREMENTS
| MATERIAL | MINIMUM GRADES | APPLICABLE GRADING RULES |
| Wood shakes of naturally durable wood | 1 | CSSB |
| Taper sawn shakes of naturally durable wood | 1 or 2 | CSSB |
| Preservative-treated shakes and shingles of naturally durable wood | 1 | CSSB |
| Fire-retardant-treated shakes and shingles of naturally durable wood | 1 | CSSB |
| Preservative-treated taper sawn shakes of Southern pine treated in accordance with AWPA U1 (Commodity Specification A, Use Category 3B and Section 5.6) | 1 or 2 | TFS |
| CSSB = Cedar Shake and Shingle Bureau. TFS = Forest Products Laboratory of the Texas Forest Services. |
1507.9.7 Attachment. Fasteners for wood shakes shall be corrosion resistant with a minimum penetration of 3/4 inch (19.1 mm) into the sheathing. For sheathing less than 1/2 inch (12.7 mm) in thickness, the fasteners shall extend through the sheathing. Each shake shall be attached with a minimum of two fasteners.
1507.9.8 Application. 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 to 5/8 inches (9.5 to 15.9 mm) for shakes and taper sawn shakes of naturally durable wood and shall be 1/4 to 3/8 inch (6.4 to 9.5 mm) for preservative taper sawn shakes. Weather exposure for wood shakes shall not exceed those set in Table 1507.9.8.
TABLE 1507.9.8 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 24 | No. 1 No. 1 | 7.5 10a |
| Preservative-treated taper sawn shakes of Southern yellow pine | 18 24 | No. 1 No. 1 | 7.5 10 |
| 18 24 | No. 2 No. 2 | 5.5 7.5 | |
| Taper sawn shakes of naturally durable wood | 18 24 | No. 1 No. 1 | 7.5 10 |
| 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. |
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 not be less than 0.019-inch (0.48 mm) (No. 26 galvanized sheet gage) corrosion-resistant metal. The valley flashing shall extend at least 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 complying with ASTM D 1970, 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.
