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Accessory Roofing Materials
Roofing material categories in the accessory family.
Asphalt-Saturated Felt Underlayment
Asphalt-saturated felt underlayment is an organic felt sheet impregnated with asphalt and installed between roof decking and asphalt shingles as a secondary water-resistive barrier. It is manufactured to ASTM D226, Standard Specification for Asphalt-Saturated Organic Felt Used in Roofing and Waterproofing, in two weights: Type I (commonly called No. 15 felt) and the heavier Type II (No. 30 felt). IRC Section R905.1.1 (Underlayment) requires labeled underlayment conforming to ASTM D226 Type I or II, or to the related ASTM D4869 steep-slope felt standard, beneath asphalt shingles. It is used almost exclusively on steep-slope roofs.
Box and Turtle Vents
A box or turtle vent is an individual static roof louver installed near the ridge to exhaust attic heat and moisture without moving parts. IRC Section R806 governs attic ventilation: R806.1 requires enclosed attics to have cross ventilation through openings protected against rain and snow entry, and R806.2 sets the minimum net free ventilating area at 1/150 of the vented space, reducible to 1/300 when a Class I or II vapor retarder is installed and 40-50 percent of the ventilating area sits in the upper attic near the ridge. Manufacturers rate individual louvers by net free area in square inches; multiple units combine with soffit intake to meet the required total on steep-slope roofs.
Drip Edge
Drip edge is a corrosion-resistant metal flashing installed along the eaves and rake edges of steep-slope shingle roofs to direct water into gutters and away from the fascia and roof deck. Under IRC Section R905.2.8.5, it must extend at least 1/4 inch below the roof sheathing and at least 2 inches back onto the deck, with adjacent pieces overlapped a minimum of 2 inches and fasteners spaced no more than 12 inches on center. Underlayment is installed over the drip edge at eaves and under the drip edge at rakes. IRC Section R903.2 separately requires that metal flashing be corrosion resistant, at least 0.019 inch thick (No. 26 galvanized sheet) or equivalent.
Ice and Water Barrier
A self-adhering, polymer-modified bituminous sheet installed at roof eaves, valleys, and other vulnerable areas to stop water intrusion from ice-dam backup on steep-slope roofs. The membrane's rubberized asphalt underside bonds directly to the deck and seals around fastener penetrations, giving continuous protection that ordinary felt underlayment cannot. IRC Section R905.1.2 permits it as an alternative to two cemented layers of underlayment in areas with a history of ice damming, requiring that the sheet comply with ASTM D1970. It is used under asphalt shingles, wood shakes, slate, and metal roof shingles on steep-slope assemblies.
Pipe Boot Flashing
Pipe boot flashing seals the roof penetration where a plumbing vent stack or soil pipe passes through an asphalt shingle roof, using a flexible collar (commonly EPDM or thermoplastic) mounted on a metal or plastic base that is woven into the shingle courses. Under the 2021 IRC, R905.2.8.4 "Other Flashing" requires that soil stack and vent pipe flashing be applied per the asphalt shingle manufacturer's printed instructions rather than a prescriptive code detail, and IRC P3103.3 separately requires the vent pipe-to-roof juncture be made watertight by an approved flashing. Where a self-adhering membrane is used to seal around the penetration, that membrane product is commonly specified to ASTM D1970.
Ridge Vent
A ridge vent is a continuous exhaust vent cut into the roof sheathing along the ridge line and covered by a rigid or shingle-over cap, letting warm, moist attic air escape as part of a balanced intake-and-exhaust system. IRC Section R806.2 sets the minimum net free ventilating area at 1/150 of the vented space, reducible to 1/300 where a Class I or II vapor retarder is installed (Climate Zones 6-8) and 40-50 percent of the ventilating area is provided by upper ventilators within 3 feet of the ridge. R806.1 requires ventilation openings to have a least dimension of 1/16 to 1/4 inch, or be covered with corrosion-resistant screening in that same range. Manufacturers publish each product's net free area (NFVA) in square inches per linear foot. Used on steep-slope roofs.
Roof Cement and Mastic
Roof cement, also called plastic cement or flashing cement, is a trowel-grade asphalt-based mastic used to seal flashing laps, felt seams, and penetrations on steep- and low-slope roofs. Modern products are formulated asbestos-free under ASTM D4586, Standard Specification for Asphalt Roof Cement, Asbestos-Free, in Type I or Type II asphalt and Class I (dry) or Class II (wet) grades. Its older sibling, ASTM D2822, covered the asbestos-containing predecessor product and was withdrawn in 2016, though IRC Table R905.9.2 still lists D2822, D3019, and D4586 together as accepted asphalt cements for built-up roof coverings. IRC Section R905.6.6 separately requires a plastic-cement top coating on cap flashing where slate roofing meets chimneys or masonry walls.
Roofing Nails
Roofing nails are the mechanical fasteners used to attach asphalt shingles to roof sheathing, driven through the shingle's nailing zone into structural decking. IRC Section R905.2.5 requires fasteners for asphalt shingles to be galvanized steel, stainless steel, aluminum, or copper roofing nails with a minimum 12-gauge (0.105-inch) shank and a minimum 3/8-inch-diameter head, complying with ASTM F1667, Standard Specification for Driven Fasteners: Nails, Spikes, and Staples. Nails must penetrate at least 3/4 inch into the roof sheathing, or fully through sheathing thinner than 3/4 inch. NRCA recommends ASTM F1667 Type I, Style 20 nails for steep-slope shingle application.
Roofing Screws and Fasteners
Roofing screws are threaded, typically self-drilling and self-tapping fasteners with integrated washered heads, used to mechanically attach exposed-fastener metal roof panels to purlins or decking and to secure insulation, cover boards, and single-ply membrane in low-slope mechanically-attached systems. Unlike smooth-shank roofing nails, these fasteners are governed less by a single material standard than by the tested roof assembly: FM Approvals Standard 4471 (Class 1 Panel Roofs) qualifies metal panel systems, including fastener type and spacing, as a complete wind-uplift assembly, while FM Approval Standard 4470 sets the corrosion-resistance test fasteners must pass for low-slope attachment. Some self-drilling steel screws also reference ASTM C1513, which covers steel tapping screws for cold-formed steel framing connections. Correct selection means matching the screw named in the specific FM or UL assembly listing being installed, not a generic product spec.
Step and Counter Flashing
Step and counter flashing form the watertight assembly used where an asphalt shingle roof plane meets a vertical sidewall, chimney, or dormer. Step flashing is a series of individual L-shaped metal pieces, one per shingle course, interwoven with the shingles as the roof is laid; counter flashing is the wall-side lap - siding, masonry counterflashing, or a cap flashing strip - that overlaps the vertical leg of the step flashing to complete the seal. IRC R905.2.8.3 (Sidewall Flashing) requires this base or step flashing be not less than 4 inches in height and 4 inches in width, and R905.2.8.1 requires corrosion-resistant metal of at least 0.019-inch nominal thickness, under the general flashing mandate of R903.2.
Synthetic Underlayment
Synthetic underlayment is a woven polypropylene or polyethylene sheet installed beneath asphalt shingles on steep-slope roofs as a secondary water-resistive barrier, replacing traditional asphalt-saturated felt. It is governed by ASTM D8257, Standard Specification for Mechanically Attached Polymeric Roof Underlayment Used in Steep Slope Roofing, a dedicated performance-based standard published in 2020 specifically for polymeric sheet products. The 2024 IRC added D8257 alongside D226, D1970, D4869, and D6757 in Table R905.1.1(1) as an accepted underlayment type. It is lighter and covers more roof area per roll than felt, and is commonly used under fastener-applied asphalt shingle roofing.
Valley Flashing
Valley flashing lines the trough where two asphalt-shingle roof planes meet, directing concentrated runoff away from the seam. IRC R905.2.8.2 governs it and distinguishes open valleys, where the lining stays exposed, from closed (cut or woven) valleys, where shingles are carried across the center. Open valleys require corrosion-resistant metal at least 24 inches wide or two-ply mineral-surfaced roll roofing complying with ASTM D3909 or ASTM D6380 Class M. Closed valleys permit one ply of smooth roll roofing at least 36 inches wide complying with ASTM D6380, the same metal or two-ply options, or self-adhering polymer-modified bitumen underlayment complying with ASTM D1970 in place of a separate lining.