South Carolina Roofing

Key Concepts

Fall protection — 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 (§1926.501(b)(10)). On a low-slope roof 50 feet or less in width, a safety monitoring system may be used alone, without a warning line (§1926.501(b)(10); Subpart M App. A confirms width is the lesser of the two primary dimensions, viewed from above).

Fall protection — steep roofs (slope greater than 4 in 12). Employees on a steep roof with unprotected sides and edges 6 feet or more above lower levels 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 are not options on steep roofs.

Key Concepts

Wood panels — NRCA thickness by rafter spacing (asphalt shingles) - 24-inch rafter spacing: minimum four-ply, nominal ¾-inch-thick plywood (actual 23/32 inch). 16-inch rafter spacing: four-ply, nominal ⅝-inch-thick plywood. These minimums provide support and fastener pull-out resistance. (NRCA Roofing Manual: Steep Slope Roof Systems, Section 2.1—Wood Panels) - Plywood used as roof sheathing should meet or exceed PS 1, "Construction and Industrial Plywood." This applies across steep-slope system types including asphalt shingle, slate, tile, metal shingle, and wood shake. (NRCA Steep Slope, Section 2.1—Wood Panels)

Wood planks and boards - Wood boards are lumber less than 2 inches thick, typically 4 to 12 inches wide. Boards thinner than nominal 1 inch are not considered strong enough to support roof loads. (NRCA Steep Slope, Section 2.2) - Asphalt shingles may be applied only over continuous wood panels or closely spaced planks/boards. Spaced ("skipped") planks or boards are not adequate substrates for asphalt shingles. (NRCA Steep Slope, Asphalt Shingle Roof Systems, Chapter 2—Roof Decks)

Key Concepts

Fire classification (IBC 2021, Chapter 15) - Class A = effective against severe fire-test exposure (§1505.2); Class B = moderate (§1505.3); Class C = light (§1505.4). - Class A, B and C assemblies required to be listed are tested to ASTM E108 or UL 790 (§1505.1). - Class A by exception: minimum 16 oz/sq ft copper sheets over combustible decks (§1505.2, Exc. 3); slate over ASTM D226 Type II underlayment over combustible decks (§1505.2, Exc. 4). - Fire-retardant-treated wood shakes/shingles must be impregnated by the full-cell vacuum-pressure process, per AWPA C1 (§1505.6).

Wind resistance of asphalt shingles - Shingles shall be tested to ASTM D7158 and meet Table 1504.2 for the maximum basic wind speed; ASTM D3161 applies only to shingles outside D7158's scope (IBC 2021 §1504.2). - ASTM D7158: Class D up to and including 90 mph, Class G up to 120 mph, Class H up to 150 mph (NRCA Steep-slope, §4.2—Wind Resistance). - ASTM D3161: Class A = 60 mph, Class D = 90 mph, Class F = 110 mph…

South Carolina Roofing Exam

Key Concepts

System classification and minimum slope - Architectural metal panel roof system on a nailable deck (new construction or roof replacement): minimum slope 3:12 (NRCA Metal Panel and SPF Roof Systems, pp. 24–25; Ch. 1—Roof System Configurations). - Structural metal panel roof system on structural framing (new construction or roof replacement): minimum slope ½:12 (NRCA, pp. 30–31, Ch. 1). - NRCA design slopes for surfaces without valleys: 3 inches per foot for architectural; ½ inch per foot for structural (NRCA, p. 47). - Valleys reduce slope: a 3:12 architectural panel slope yields an approximate valley slope of 2⅛:12 (NRCA, p. 47). - Code minimums: standing-seam metal roof panel systems, 1/4:12 (2%); lapped, nonsoldered panels with applied lap sealant, 1/2:12; lapped panels without sealant, 3:12 (SC Building Code 2021, §1507.4.2). - Metal roof panel coverings must be applied to a solid or closely fitted deck except where the covering is specifically designed for spaced supports (SC Building Code 2021, §1507.4.1).

Key Concepts

Drip edge (steep-slope) - Underlayment is installed over drip edges along eaves; drip edges are installed over underlayment along rake edges (IBC 2021 / SC Building Code 2021, Section 1507.2.8.3). - Vertical leg of drip edges: not less than 1-1/2 inches wide, extending not less than 1/4 inch below sheathing (Section 1507.2.8.3). - Mechanically fastened at intervals not greater than 12 inches on center (Section 1507.2.8.3). NRCA suggests fastening at approximately 12 inches on center, slightly staggered; spacing may be closer in high-wind regions (NRCA Architectural Metal Flashing, Page 97, Section 3.1).

Valleys by roof covering - Clay/concrete tile: valley flashing extends not less than 11 inches from the centerline each way, with a splash diverter rib not less than 1 inch high at the flow line (IBC 2021, Section 1507.3.9). - Metal roof shingles: 8 inches from centerline each way, splash diverter rib not less than ¾ inch high (IBC 2021, Section 1507.5.7). - Slate: valley flashing not less than 15 inches wide, sheet metal with minimum uncoated thickness **0.0179 inch…

Key Concepts

Reroofing definitions (NRCA Steep-slope, Ch. 6.1): Reroofing = re-covering or tearing off and replacing an existing roof covering. Re-covering = installing an additional covering over a prepared existing covering. Replacement = removing the existing covering, repairing damaged substrate, installing new.

Code — general (IBC/SC Building Code 2021, §1512.1): Recover/replacement materials must comply with Chapter 15. Exception 1: replacement or recover of existing low-slope coverings need not meet the ¼:12 (2-percent) minimum design slope where the roof provides positive roof drainage. Exception 2: secondary (overflow) drains/scuppers of §1502.2 not required where positive drainage exists.

Roof replacement (§1512.2): Replacement includes removal of all existing layers down to the roof deck. Exception: an ice barrier membrane adhered to the deck may remain and be covered with an additional layer of ice barrier membrane per §1507.

Key Concepts

Membrane types and materials. EPDM sheets are the only thermoset materials commonly used in single-ply roof membranes in North America; once cured, thermoset sheets can only be bonded to like material with liquid-applied adhesive or adhesive seam tape (Chapter 5—Roof Membranes, Section 5.4). Thermoplastic sheets (PVC, PVC alloys such as CPA, EIP and NBP, KEE, TPO) repeatedly soften when heated and harden when cooled, and typically are seamed by heat welding with hot air (Section 5.4).

EPDM classification. ASTM D4637 Type I = nonreinforced EPDM; Type II = EPDM reinforced internally with scrim or fabric; Type III = EPDM sheets with fabric backing (Chapter 5, Pages 216-217).

Minimum sheet thicknesses (NRCA recommendations). PVC: minimum nominal 45 mils for conventional single-ply roof systems; PVC is produced in 36, 45, 60, 72 and 90 mils (Chapter 5, Page 217; Section 5.4—PVC). TPO: minimum nominal 60-mil sheets, or thicker if project conditions warrant, because thicker sheets carry more UV/heat-aging stabilizers and offer greater thickness over scrim, puncture resistance and breaking strength (Chapter 5, Page 220).…

Key Concepts

Bitumen types and properties - Asphalt complying with ASTM D312, Type III is generally appropriate for interply moppings in built-up membrane application where the slope of the completed membrane is 1:12 or less; Type IV is suggested for slopes greater than 1:12 (NRCA Membrane Roof Systems, Ch. 5, p. 192). - Softening-point ranges (Section 5.2, Asphalt Softening Point table): Type I 135 F–151 F; Type II 158 F–176 F; Type III 185 F–205 F; Type IV 210 F–225 F. - Kettle and tanker temperatures should be maintained at 550 F or lower, and material should never be heated to or above the actual flash point (Ch. 5, p. 199). NRCA recommends kettle/tanker temperatures be kept lower than 25 F below the asphalt's actual FP temperature. ASTM D312-15 raised the minimum FP from 500 F to 575 F; as a result ASTM D312 indicates a maximum heating temperature of 550 F. FP is tested by ASTM D92. - EVT (measured per ASTM D4402): 125 centipoise for mop application, **75 cP for mechanical spreader…