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 1507.7 - Slate shingles
Current through Register 1531, September 27, 2024
The installation of slate shingles shall comply with the provisions of this section.
1507.7.1 Deck requirements. Slate shingles shall be fastened to solidly sheathed roofs.
1507.7.2 Deck slope. Slate shingles shall only be used on slopes of four units vertical in 12 units horizontal (4:12) or greater.
1507.7.3 Underlayment. Underlayment shall comply with ASTM D 226, Type I or ASTM D 4869.
1507.7.4 Ice barrier. 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, an ice barrier that consists of at least two layers of underlayment cemented together or of a self-adhering polymer-modified bitumen sheet shall 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.
1507.7.5 Material standards. Slate shingles shall comply with ASTM C 406.
1507.7.6 Application. Minimum headlap for slate shingles shall be in accordance with Table 1507.7.6. Slate shingles shall be secured to the roof with two fasteners per slate.
TABLE 1507.7.6 SLATE SHINGLE HEADLAP
SLOPE | HEADLAP (inches) |
4:12 < slope < 8:12 | 4 |
8:12 < slope < 20:12 | 3 |
Slope >= 20:12 | 2 |
For SI: 1 inch = 25.4 mm. |
1507.7.7 Flashing. Flashing and counterflashing shall be made with sheet metal. Valley flashing shall be a minimum of 15 inches (381 mm) wide. Valley and flashing metal shall be a minimum uncoated thickness of 0.0179-inch (0.455 mm) zinc-coated G90. Chimneys, stucco or brick walls shall have a minimum of two plies of felt for a cap flashing consisting of a 4-inch-wide (102 mm) strip of felt set in plastic cement and extending 1 inch (25 mm) above the first felt and a top coating of plastic cement. The felt shall extend over the base flashing 2 inches (51 mm).