Louisiana Residential Roofing

Key Concepts

Asphalt shingle standards - ASTM D3462, "Standard Specification for Asphalt Shingles Made from Glass Felt and Surfaced with Mineral Granules," addresses tear strength, fastener pull-through resistance and pliability. NRCA recommends designers specify fiberglass-reinforced asphalt shingles complying with D3462 (NRCA Steep Slope, Sec. 4.1—Asphalt Shingle Standards). The code requires the same: "Asphalt shingles shall comply with ASTM D3462" (IBC 2021, Sec. 1507.2.4). - ASTM D3018, "Standard Specification for Class A Asphalt Shingles Surfaced with Mineral Granules," addresses fire test classification, wind resistance, and loss of volatile matter after heating (Sec. 4.1). - AC438, "Acceptance Criteria for Alternative Asphalt Roofing Shingles," is a performance-based alternative to ASTM D3462 for code compliance (Sec. 4.1). - Mineral granules protect asphalt from UV/weathering, improve outside-fire resistance, provide design/color variety, and add weight for wind resistance. They are not a vapor retarder (Sec. 4.1—Surfacing). - Fillers (mineral additives) stabilize the bitumen, reduce natural flow, and increase fire resistance (Sec. 4.1—Asphalt and Fillers). - Fasteners: minimum 12-gage [0.105 inch] shank with minimum 3/8-inch-diameter head (IBC 2021, Sec. 1507.2.5).

Underlayments - ASTM D4869 — asphalt-saturated organic felt shingle underlayment; Types I–IV. Type II, #13 = ASTM D226 Type I (No. 15 felt); Type IV, #26 = ASTM D226 Type II (No. 30 felt) (Sec. 3.1). - ASTM D6757 — "Underlayment Felt Containing Inorganic Fibers Used in Steep-slope Roofing" (Sec. 3.1). - NRCA recommends asphalt felt underlayments comply with ASTM D4869, Type II (No. 15), or ASTM D6757 because heavier underlayments may wrinkle and telegraph through shingles (Sec. 3.1). - ASTM D8257 — mechanically attached polymeric (synthetic) underlayments; approved December 2020, referenced in IBC 2024 and IRC 2024 (Sec. 3.1). - Impermeable synthetic sheet = water…

Key Concepts

Asphalt shingle fastening. Full-length three-tab strip shingles require a minimum of four roofing nails per strip, in a horizontal line about ⅝ inch above the tops of the cutouts (NRCA, Sec. 4.2—Asphalt Shingle Roof System Design and Installation). Nails must be round-headed, sharp-pointed 0.12-inch (11-gauge) galvanized or equivalent corrosion-resistant, with ⅜-inch to 7⁄16-inch heads (Sec. 4.2—Fasteners). Nails extend minimum ⅛ inch through the underside of plywood/wood panel decks less than ¾ inch thick; at least ¾-inch penetration into wood plank or board decks (Sec. 4.2—Fasteners). At 18:12 and greater, NRCA recommends six nails plus hand-tabbing with roof cement spots about 1 inch in diameter (Sec. 4.2). For six-nail attachment of standard-sized laminated shingles in high-wind regions, nails go in a line about 5½ inches above the butt edge, 1 inch in from each end with four evenly spaced between (Sec. 4.2).

Layout. Standard three-tab shingles are 12 in. × 36 in. (Sec. 4—Shapes and Styles); typical exposure is 5 inches for standard 36-inch strip shingles and 5⅝ inches for metric-sized strip shingles (Sec. 4.2—Exposure and Appearance). The common offset is the 6-inch method (Sec. 4.2—Offset Patterns). Starter course: end joints offset minimum 5 inches from the first course, fastened 1½ to 3 inches above the downslope perimeter edges, and roofing material even with or no more than ¾ inch beyond T-type drip edge (Sec. 4.2—Starter Courses).

Based on IBC 2021, IPC 2021 and The NRCA Roofing Manual: Steep-slope Roof Systems

Key Concepts

Primary roof drainage (IBC 1502) - Design and installation of roof drainage systems shall comply with Section 1502, Section 1611 of the IBC, and Chapter 11 of the International Plumbing Code (IBC 2021, 1502.1). - Secondary (emergency overflow) roof drains or scuppers are required where the roof perimeter construction extends above the roof in such a manner that water will be entrapped if the primary drains allow buildup for any reason (IBC 2021, 1502.2).

Scuppers (IBC 1502.3) - Scuppers used for secondary (emergency overflow) drainage shall not have an opening dimension of less than 4 inches (102 mm). - The flow through the primary system shall not be considered when locating and sizing scuppers.

Gutters (IBC 1502.4) - Gutters and leaders on the outside of buildings shall be noncombustible material or not less than Schedule 40 plastic pipe — except Group R-3, private garages, and buildings of Type V construction. A single-family home is Group R-3.

Crickets and saddles (IBC 1503.5) - Required on the ridge side of any chimney or penetration greater than 30 inches (762 mm) wide measured perpendicular to the slope. - Coverings shall be sheet metal or of the same material as the roof covering. - NRCA recommends crickets at the upslope side when the chimney or curb is more than 24 inches wide; backer flashing is generally limited to penetrations 24 inches wide or less (NRCA Steep Slope, Asphalt Shingle — Ch. 7). - A cricket deck flange should have hemmed edges and extend upslope under asphalt shingles a minimum of 8 inches (a backer flashing requires 16…

Key Concepts

Slope, pitch and span - Slope = (Total Rise / Total Run) × 12, expressed as rise in inches per 12 inches of run (Roofing Construction and Estimating, p. 10). - Pitch = Total Rise / Total Span; Slope = 2 × Pitch (RC&E, p. 11).

Roof geometry for estimating - Conventional hip roof: Ridge = L − [2 × (W/2)] = L − W (RC&E, p. 22). - Hip rafter plan length = 1.414 × run (RC&E, Appendix C, Equation 1-14). - Unequal-slope valleys: actual valley length = run of the low-sloping roof × valley length factor from Appendix B (RC&E, p. 22, Example 1-15). - Positive method = divide into rectangles and add; negative method = extend roof lines to one large rectangle and subtract non-roof areas. Both give identical results (RC&E, Ch. 1, pp. 7–8).

Deck type by roof covering - Wood shakes over spaced sheathing: 1 × 6 boards, spacing equal to shake exposure; wood shingles use 1 × 4 (RC&E, p. 30). IBC 1507.9.1 requires spaced boards not less than 1 × 4 nominal, spaced on centers equal to weather exposure. - Solid sheathing required where the average daily January temperature is 25°F or less, or where ice may form at eaves backing up water (IBC 1507.9.1.1). - Concrete and clay tile: solid sheathing only; spaced lumber sheathing permitted only in Seismic Design Categories A, B and C (IBC 1507.3.1). Air-permeable rigid tile requires solid sheathing designed as components and cladding (IBC 1609.5.3).

Key Concepts

Fall protection trigger height. For roofing work on low-slope roofs, OSHA requires fall protection at 6 ft (29 CFR 1926 Subpart M).

Low-slope roofs (slope ≤ 4 in 12). Employees engaged in roofing activities on low-slope roofs with unprotected sides and edges 6 feet or more above lower levels may be protected by guardrail systems, safety net systems, personal fall arrest systems, or a combination of warning line system and safety monitoring system, among other options — §1926.501(b)(10).

Steep roofs (slope greater than 4 in 12). Employees must be protected by guardrail systems with toeboards, safety net systems, or personal fall arrest systems — §1926.501(b)(11). Warning line and safety monitoring systems, alone or combined, are not permitted on steep roofs.

Warning line placement. When mechanical equipment is not being used, the warning line shall be erected not less than 6 feet (1.8 m) from the roof edge — §1926.502(f)(1)(i). When mechanical equipment is being used: not less than 6 feet from the edge parallel to the direction of operation, and not less than 10 feet (3.1 m) from the edge perpendicular to the direction of operation — §1926.502(f)(1)(ii). The warning line shall be erected around all sides of the roof work area — §1926.502(f)(1).