Florida Roofing Contractors General Trade Knowledge Exam

Key Concepts

Slope and drainage - Most model and local building codes require a minimum ¼:12 roof slope for low-slope roof assemblies, except coal tar, which requires a minimum ⅛:12 (NRCA Membrane Roof Systems—2023, Sec. 4.15, p. 172). Walker's Div. 07 adds that coal tar pitch is not recommended for roofs with an incline in excess of 1 inch per foot. - For reroofing (re-cover or tear-off and replacement), codes do not require the new system to meet minimum design slope provided there is positive roof drainage (NRCA Ch. 2, p. 84). - Saddle/cricket material should be twice the slope of the adjacent field; maximum slope of saddle/cricket material is ½:12 (NRCA Ch. 4, p. 177; Ch. 2, p. 84). Crickets go on the high side of curbs 24 inches and wider (Ch. 10, pp. 327–328).

Key Concepts

Asphalt shingle materials and ratings - Fiberglass shingles have a fiberglass base mat saturated and covered with flexible asphalt and surfaced with mineral granules; they contain more asphalt than organic-based shingles (Roofing Construction and Estimating, Ch. 4—Asphalt Shingles). - UL fire classes: Class A = severe fire exposure, Class B = moderate, Class C = light, "exposure" meaning fire from sources outside the building (Ch. 4, p. 4-2). - To bear a UL "wind-resistant" label, a shingle must withstand winds up to 63 mph for two hours without a single tab being uplifted (Ch. 4—Asphalt Shingles, p. 75). - Asphalt strip shingles weigh 135 to 390 pounds per square; they are made 35 5/16 in. to 42 in. long and 12 to 14¼ in. wide, with recommended exposures of 4 to 6 in. (Ch. 4—Asphalt Strip Shingles). - Standard application: slopes 4 in 12 through 21 in 12; slopes as low as…

Key Concepts

Metal types and coatings - Galvalume® alloy coating is reported to be 55% aluminum and 45% zinc by weight; the zinc phase protects sacrificially and the aluminum phase acts as a barrier (NRCA Metal Panel and SPF Roof Systems—2024, Pages 75-76, Sec. 4.1—Galvalume). - Uncoated zinc cladding should be ventilated on the back side with a minimum ⅜ of an inch of uninterrupted ventilation airspace, plus intake and exhaust openings — typically achieved with a drainage mat; otherwise use factory back-coated material (2024 Metal Panel manual, Page 83, Sec. 4.1—Zinc). - Aluminum Alloy 5005 has excellent corrosion resistance and good workability and is typically specified where anodizing is required (NRCA Architectural Metal Flashing…—2022, Page 22, Sec. 1.1—Aluminum).

Key Concepts

Membrane types and thicknesses - NRCA recommends designers specify PVC sheets with a minimum nominal thickness of 45 mils for conventional single-ply roof systems; PVC sheets are produced in 36, 45, 60, 72 and 90 mils (Section 5.4—Single-ply Roof Membranes, PVC; p. 217). - For heat-induction-welded systems, NRCA recommends PVC, KEE and TPO membranes with a minimum thickness of 60 mils (Section 5.4, p. 227). This is a separate case from the 45-mil conventional PVC recommendation. - TPO is seamed by hot-air welding; TPO sheets come in 45, 60, 72, 80 and 90 mils. The U.S. product standard for TPO is ASTM D6878; for KEE it is ASTM D6754, which requires KEE polymer to make up a minimum 50% by weight of the polymer content of the sheet (Section 5.4). - EPDM is the only thermoset material commonly used in North America; NRCA recognizes four attachment methods for EPDM: adhered, mechanically attached,…

Key Concepts

Asphalt heating and application temperatures - Kettle and tanker temperatures should be maintained at 550 F or lower, and materials should never be heated to or above the actual flash point (Ch. 5, Page 199). - For polymer-modified bitumen membrane application, bitumen should be hot enough to promote thorough adhesion and lamination of plies, but not heated above 550 F maximum, and never to or above the actual flash point (Ch. 5, Section 5.3, Page 212). - For hot-mopped SBS cap sheets, the EVT range recommendation generally is not applicable; most manufacturers recommend the mopping asphalt be as hot as possible without overheating in the kettle or tanker — usually hotter than the EVT — to obtain fusion with the modified sheet. The ±25 F EVT field range applies to hot-applied built-up membrane work (Section 5.3, Pages 203 and 212). - EVT is the temperature at which 125 centipoise is attained (mop…

Key Concepts

Roof decks (NRCA, Clay and Concrete Tile Roof Systems, Chapter 2—Roof Decks) - NRCA recommends designers specify roof deck slopes for tile roof systems at 4:12 or greater; building codes permit roof tile on deck slopes at 2½:12. Below 4:12, with certain profiles water can flow backward on the tile top surface — consult the tile manufacturer and local codes. - Plywood should meet or exceed PS 1, "Construction and Industrial Plywood." For tile, NRCA prefers minimum four-ply, nominal ⅝-inch (actual 19⁄32-inch) plywood for 16-inch rafter spacings and four-ply, nominal ¾-inch (actual 23⁄32-inch) for 24-inch rafter spacings (Section 2.1). - OSB is not recommended as a substrate for clay and concrete tile — because of long-term performance concerns and the long-term life expectancy of tile roof systems. Deck material of comparable long-term expected service life is important (Section 2.1). - Wood boards are lumber less than 2 inches thick, typically **4 to…

Key Concepts

Definitions. Waterproofing is "treatment of a surface or structure to prevent the passage of water under hydrostatic conditions"; dampproofing is "the treatment of a surface to resist the passage of moisture in the absence of hydrostatic pressure" (NRCA Waterproofing Manual, 2nd ed., Waterproofing Construction Details Introduction; Section 3.1). Dampproofing must not be used on slabs on grade or foundation walls subject to hydrostatic pressure, on suspended structural decks over habitable space, or on planters, pools or other water-containment structures (Section 3.1).

Positive vs. negative side. Positive (exterior) side = membrane installed between its substrate and the source of water; negative (interior) side = substrate is between the system and the source of water (Construction Details Introduction). Only cementitious and crystalline systems are appropriate for negative (interior) side waterproofing of below-grade walls (Sections 2.3.2.2 and 2.4.2.2).

Key Concepts

Downspouts (SMACNA Architectural Sheet Metal Manual, 7th ed., Page 1.1) - Downspouts shall be constructed with conductor heads every 40 ft (12.2 m) to admit air and prevent a vacuum. - Downspouts of less than 7.00 in.² (4515 mm²) cross section should not be used except for small areas such as porches and canopies. - The downspout size must be constant throughout its length, must suit the bottom width of the gutter, and the gutter outlet capacity should match the downspout capacity. Offsets of more than 10 ft (3.0 m) can affect drainage capacity. - Support straps (Figure 1-35, Page 1.80): downspouts 10 ft (2.5 m) or less get two straps; longer downspouts are supported at 10 ft (2.5 m) maximum intervals.

Key Concepts

Ladders. Minimum clear distance between side rails for all portable ladders (including job-made) is 11 1/2 inches (29 cm) — §1926.1053(a)(4)(ii). Separate figures: 16 inches for individual-rung/step ladders and other fixed ladders (§1926.1053(a)(4)(i)); 15 inches clear width to the nearest permanent object each side of the centerline of a fixed ladder without a cage or well (§1926.1053(a)(17)); 14 inches maximum rung spacing (§1926.1053(a)(3)(i)). Side rails must extend 3 ft (36 in) above the landing surface, and ladders are set at the 4-to-1 angle (§1926.1053(b)(1) and (b)(5)(i)).

Scaffolds. A supported scaffold with a height-to-base-width ratio (including outrigger supports, if used) of more than four to one (4:1) must be restrained from tipping by guying, tying, bracing, or equivalent means — §1926.451(c)(1). The 2:1 figure is the movement limit for riding on mobile scaffolds (§1926.452(w)(6)(ii)), not a tipping trigger. Pole scaffolds over 60 feet and tube and coupler scaffolds over 125 feet must be…