Roof Assemblies
Roof coverings, flashing, drainage, and roofing materials
Sections
Scope.
The provisions of this chapter shall govern the design, materials, construction and quality of roof assemblies. SECTION R902 FIRE CLASSIFICATION ES
Roofing Covering Materials
FIRE CLASSIFICATION: All roofing materials must be tested per ASTM E108 or UL 790. Class A is most fire-resistant (required within 3 feet of lot lines). Most architectural asphalt shingles are Class A rated. Verify fire rating on product packaging or manufacturer documentation.
Fire-retardant-treated shingles and shakes.
Fire-retardant-treated wood shakes and shingles shall be treated by impregnation with chemicals by the full-cell vacuum-pressure process, in accordance with AWPA C1.
Building-integrated photovoltaic product.
Building-integrated photovoltaic (BIPV) products installed as the roof covering shall be tested, listed and labeled for fire classification in accordance with UL 7103. Class A, B or C BIPV products shall be installed where the edge of the roof is less than 3 feet (914 mm) from a lot line.
Rooftop-mounted photovoltaic panel systems.
Rooftop-mounted photovoltaic panel systems installed on or above the roof covering shall be tested, listed and identified with a fire classification in accordance with UL 2703.
Weather Protection
Parent section for weather protection requirements including decking, flashing, and crickets.
Roof Drainage
Section R903.1 — Roof Drainage. Unless roofs are sloped to drain over the roof edges, roof drains shall be installed at each low point of the roof. Where required by the building official, overflow drains shall b...
Flashing
General flashing requirements for roof assemblies. Metal flashing must be corrosion-resistant, minimum 26 gauge.
Step Flashing
Section R903.2.1 — Step Flashing. Step flashing at the juncture of roof slopes and vertical surfaces shall consist of individual pieces of flashing material not less than 4 inches in width by 4 inches in height, in...
Crickets and Saddles
CRICKETS & SADDLES - Required on ridge side of chimneys/penetrations >30" wide.
Weather Protection
General weather protection requirement for all roof covering systems.
Roof Drainage
Roofs must drain adequately without ponding. Drains required at low points unless roof slopes to edges.
Secondary (Emergency Overflow) Drains or Scuppers
Secondary emergency overflow drains or scuppers required where roof perimeter extends above roof (parapet walls). Overflow drains same size as primary with inlet 2 inches above low point, OR scuppers 3x size of drains with 4-inch minimum opening height.
Manufacturers Requirements
MANUFACTURER REQUIREMENTS - Roof assemblies MUST be applied per code AND manufacturer installation instructions.
Compatibility of materials.
Roof assemblies shall be of materials that are compatible with each other and with the building or structure to which the materials are applied.
Material specifications and physical characteristics.
Roof covering materials shall conform to the applicable standards listed in this chapter.
Product identification.
Roof covering materials shall be delivered in packages bearing the manufacturer’s identifying marks and approved testing agency labels required. Bulk shipments of materials shall be accompanied by the same information issued in the form of a certificate or on a bill of lading by the manufacturer.
Requirements for Roof Coverings
Comprehensive section covering underlayment, asphalt shingles, metal panels, tile, and other roof covering systems.
Roof Covering Materials
Roof covering materials must be installed per code and manufacturer instructions. Code provisions take precedence over manufacturer instructions when conflicts exist.
Metal Roof Shingles
Section R905.10 — Metal Roof Shingles. Metal roof shingle roof coverings shall be installed on roof slopes of 3 units vertical in 12 units horizontal (3:12) or greater. Metal roof shingles shall comply with UL 580 for u...
Deck requirements.
Metal roof panel roof coverings shall be applied to solid or spaced sheathing, except where the roof covering is specifically designed to be applied to spaced supports.
Material Standards
METAL PANELS - Must meet standards in Table R905.10.2. Corrosion resistant required.
Deck Slope
METAL PANEL SLOPES - Lapped without sealant: 3:12. Lapped with sealant: 0.5:12. Standing seam: 0.25:12.
Attachment.
Metal roof panels shall be secured to the supports in accordance with this chapter and the manufacturer’s installation instructions. In the absence of manufacturer’s installation instructions, the following fasteners shall be used: 1.
Underlayment.
Underlayment shall comply with Section R905.1.1.
Underlayment
Approved underlayment is required for various roof covering types. Most of Nevada has Vult < 140 mph, requiring standard underlayment compliance.
Modified Bitumen Roofing
Section R905.11 — Modified Bitumen Roofing. Modified bitumen membrane roofing shall be installed on roof slopes of 1/4 unit vertical in 12 units horizontal (1/4:12) or greater. The membrane shall be mechanically fastened, ad...
Slope.
Modified bitumen roofing shall have a design slope of not less than one-fourth unit vertical in 12 units horizontal (2-percent slope) for drainage.
Material standards.
Modified bitumen roofing shall comply with the standards in Table R905.11.2.
Base sheet.
A base sheet that complies with the requirements of Section 1507.11.2 of the International Building Code, ASTM D1970 or ASTM D4601 shall be permitted to be used with a modified bitumen cap sheet.
Application.
Modified bitumen roofs shall be installed in accordance with this chapter and the manufacturer’s instructions.
Ice Barriers
Section R905.1.2 — Ice Barriers. In areas where the average daily temperature in January is 25 degrees Fahrenheit or less, an ice barrier that consists of not less than two layers of underlayment cemented together...
Thermoset single-ply roofing.
The installation of thermoset single-ply roofing shall comply with the provisions of this section.
Slope.
Thermoset single-ply membrane roofs shall have a design slope of not less than 1/4 unit vertical in 12 units horizontal (2-percent slope) for drainage.
Material standards.
Thermoset single-ply roof coverings shall comply with ASTM D4637 or ASTM D5019.
Application.
Thermoset single-ply roofs shall be installed in accordance with this chapter and the manufacturer’s instructions.
Thermoplastic single-ply roofing.
The installation of thermoplastic single-ply roofing shall comply with the provisions of this section.
Slope.
Thermoplastic single-ply membrane roofs shall have a design slope of not less than 1/4 unit vertical in 12 units horizontal (2-percent slope).
Material standards.
Thermoplastic single-ply roof coverings shall comply with ASTM D4434, D6754 or D6878.
Application.
Thermoplastic single-ply roofs shall be installed in accordance with this chapter and the manufacturer’s instructions.
Sprayed Polyurethane Foam Roofing
Section R905.14 — Sprayed Polyurethane Foam Roofing. Sprayed polyurethane foam roofing shall be installed on roof slopes of 1/4 unit vertical in 12 units horizontal (1/4:12) or greater. The foam shall have a minimum thickness of 1 in...
Slope.
Sprayed polyurethane foam roofs shall have a design slope of not less than 1/4 unit vertical in 12 units horizontal (2-percent slope) for drainage.
Material standards.
Spray-applied polyurethane foam insulation shall comply with ASTM C1029, Type III or IV or ASTM D7425.
Application.
Foamed-in-place roof insulation shall be installed in accordance with this chapter and the manufacturer’s instructions. A liquid-applied protective coating that complies with Table R905.14.3 shall be applied not less than 2 hours nor more than 72 hours following the application of the foam.
Foam plastics.
Foam plastic materials and installation shall comply with Section R316.
Liquid-applied roofing.
The installation of liquid-applied roofing shall comply with the provisions of this section.
Slope.
Liquid-applied roofing shall have a design slope of not less than 1/4 unit vertical in 12 units horizontal (2-percent slope).
Material standards.
Liquid-applied roofing shall comply with ASTM C836, C957, D1227, D3468, D6083, D6694 or D6947.
Application.
Liquid-applied roofing shall be installed in accordance with this chapter and the manufacturer’s installation instructions.
Photovoltaic shingles.
The installation of photovoltaic shingles shall comply with the provisions of this section, Section R324 and NFPA 70.
Deck requirements.
Photovoltaic shingles shall be applied to a solid or closely-fitted deck, except where the roof covering is specifically designed to be applied over spaced sheathing.
Deck slope.
Photovoltaic shingles shall be used only on roof slopes of 2 units vertical in 12 units horizontal (2:12) or greater.
Underlayment.
Underlayment shall comply with Section R905.1.1.
Ice barrier.
Where required, ice barriers shall comply with Section R905.1.2.
Material standards.
INSIGHTS Photovoltaic shingles shall be listed and labeled in accordance with UL 7103 or with both UL 61730-1 and UL 61730-2. INSIGHTS (2)
Attachment.
Photovoltaic shingles shall be attached in accordance with the manufacturer’s installation instructions.
Wind resistance.
Photovoltaic shingles shall comply with the classification requirements of Table R905.16.6 for the appropriate maximum basic wind speed.
Building-integrated photovoltaic (BIPV) roof panels applied directly to the roof deck.
The installation of BIPV roof panels shall comply with the provisions of this section, Section R324 and NFPA 70.
Deck requirements.
BIPV roof panels shall be applied to a solid or closely-fitted deck, except where the roof covering is specifically designed to be applied over spaced sheathing.
Deck slope.
BIPV roof panels shall be used only on roof slopes of 2 units vertical in 12 units horizontal (17-percent slope) or greater.
Underlayment.
Underlayment shall comply with Section 905.1.1.
Ice barrier.
Where required, an ice barrier shall comply with Section R905.1.2.
Ice barrier.
In areas where there has been a history of ice forming along the eaves causing a backup of water, as designated in Table R301.2, an ice barrier that consists of not less than two layers of underlayment cemented together or of a self-adhering polymer-modified bitumen sheet shall be used in lieu of no...
Material standards.
INSIGHTS BIPV roof panels shall be listed and labeled in accordance with UL 7103 or with both UL 61730-1 and UL 61730-2. INSIGHTS (2)
Attachment.
BIPV roof panels shall be attached in accordance with the manufacturer’s installation instructions. ➡ SECTION R906 ROOF INSULATION ES
Asphalt Shingles
Asphalt shingles require minimum 2:12 slope. Double underlayment required for slopes between 2:12 and 4:12.
Sheathing Requirements for Asphalt Shingles
Asphalt shingles require solid sheathing — 7/16" minimum for 24" OC spacing.
Slope Requirements for Asphalt Shingles
Section R905.2.2 — Slope Requirements for Asphalt Shingles. Asphalt shingles shall only be used on roof slopes of 2 units vertical in 12 units horizontal (2:12) or greater. For roof slopes from 2:12 up to 4:12, double underlayment applicati...
Underlayment.
Underlayment shall comply with Section R905.1.1.
Wind Resistance
Asphalt shingles must be rated for local wind speeds per ASCE 7. Nevada typically requires standard wind-resistant shingles (not hurricane-rated).
Wind resistance of asphalt shingles.
Asphalt shingles shall be tested in accordance with ASTM D7158. Asphalt shingles shall meet the classification requirements of Table R905.2.4.1 for the appropriate ultimate design wind speed.
Fasteners.
Fasteners for asphalt shingles shall be galvanized steel, stainless steel, aluminum or copper roofing nails, minimum 12-gage [0.105 inch (3 mm)] shank with a minimum 3/8-inch-diameter (9.5 mm) head, complying with ASTM F1667, of a length to penetrate through the roofing materials and not less than 3...
Attachment of Asphalt Shingles
Section R905.2.6 — Attachment of Asphalt Shingles. Asphalt shingles shall be fastened to the roof deck with not fewer than four fasteners per strip shingle or two fasteners per individual shingle. Where the ultimate design wind spe...
Flashing
Metal flashing required at critical roof locations (walls, gutters, slope changes, openings). Minimum thickness 0.019 inch (26 gauge galvanized sheet).
Ice Barrier
ICE BARRIER REQUIRED: Virginia Climate Zones 4A/5A mandate ice barrier at ALL eaves. MINIMUM: 24 inches past exterior wall line. RECOMMENDED: 36 inches or second course line. Use self-adhering polymer-modified bitumen membrane (Grace Ice & Water Shield, GAF StormGuard, CertainTeed WinterGuard, or equivalent ASTM D1970 compliant product).
Flashing (Asphalt Shingles)
Flashing requirements specific to asphalt shingle installations.
Base Flashing
BASE FLASHING - Min 26 gauge galvanized metal OR 77 lb mineral roll roofing.
Valley Flashing
VALLEY FLASHING: OPEN VALLEYS require 24" minimum width metal flashing (28-gauge galv. steel or equiv.). CLOSED VALLEYS require 36" minimum roll roofing or ice & water shield (ASTM D1970). Ice & water shield in valleys is BEST PRACTICE for Virginia climate. W-metal valleys provide superior water channeling.
Sidewall Flashing
SIDEWALL FLASHING - Step-flashing method required. Minimum 4" width.
Other flashing.
Flashing against a vertical front wall, as well as soil stack, vent pipe and chimney flashing, shall be applied in accordance with the asphalt shingle manufacturer’s printed instructions.
Drip Edge
DRIP EDGE - Required at eaves/gables. 1/4" min extension below sheathing, 2" back on roof. Fastened 12" o.c.
Clay and Concrete Tile
Section R905.3 — Clay and Concrete Tile. Clay and concrete roof tile shall be installed on roof slopes of 2-1/2 units vertical in 12 units horizontal (2.5:12) or greater. Clay tile shall comply with ASTM C1167 and concret...
Deck requirements.
INSIGHTS Concrete and clay tile shall be installed only over solid sheathing. Exception:Spaced lumber sheathing in accordance with Section R803.1 shall be permitted in Seismic Design Categories A, B and C.
Deck slope.
Clay and concrete roof tile shall be installed on roof slopes of 21/2 units vertical in 12 units horizontal (25-percent slope) or greater.
Underlayment.
Underlayment shall comply with Section R905.1.1.
Clay tile.
Clay roof tile shall comply with ASTM C1167.
Concrete tile.
Concrete roof tile shall comply with ASTM C1492.
Fasteners.
INSIGHTS Nails shall be corrosion resistant and not less than 11-gage [0.120 inch (3 mm)], 5/16-inch (11 mm) head, and of sufficient length to penetrate the deck not less than 3/4 inch (19 mm) or through the thickness of the deck, whichever is less.
Application.
INSIGHTS Tile shall be applied in accordance with this chapter and the manufacturer’s installation instructions, based on the following: 1. Climatic conditions.
Flashing.
At the juncture of roof vertical surfaces, flashing and counterflashing shall be provided in accordance with this chapter and the manufacturer’s installation instructions and, where of metal, shall be not less than 0.019 inch (0.5 mm) (No. 26 galvanized sheet gage) corrosion-resistant metal.
Metal Roof Shingles
Parent section for metal roof shingle requirements.
Deck requirements.
Metal roof shingles shall be applied to a solid or closely fitted deck, except where the roof covering is specifically designed to be applied to spaced sheathing.
Deck Slope
METAL SHINGLES SLOPE - Minimum 3:12 slope required.
Underlayment.
Underlayment shall comply with Section R905.1.1.
Ice barrier.
Where required, ice barriers shall comply with Section R905.1.2.
Material standards.
Metal roof shingle roof coverings shall comply with Table R905.10.3(1). The materials used for metal roof shingle roof coverings shall be naturally corrosion resistant or be made corrosion resistant in accordance with the standards and minimum thicknesses listed in Table R905.10.3(2).
Wind resistance of metal roof shingles.
INSIGHTS Metal roof shingles applied to a solid or closely fitted deck shall be tested in accordance with ASTM D3161, FM 4474, UL 580 or UL 1897.
Application.
Metal roof shingles shall be secured to the roof in accordance with this chapter and the approved manufacturer’s installation instructions.
Flashing.
Roof valley flashing shall be of corrosion-resistant metal of the same material as the roof covering or shall comply with the standards in Table R905.10.3(1).
Mineral-surfaced roll roofing.
The installation of mineral-surfaced roll roofing shall comply with this section.
Deck requirements.
Mineral-surfaced roll roofing shall be fastened to solidly sheathed roofs.
Deck slope.
Mineral-surfaced roll roofing shall not be applied on roof slopes below 1 unit vertical in 12 units horizontal (8-percent slope).
Underlayment.
Underlayment shall comply with Section R905.1.1.
Ice barrier.
Where required, ice barriers shall comply with Section R905.1.2.
Material standards.
Mineral-surfaced roll roofing shall conform to ASTM D3909 or ASTM D6380, Class M.
Application.
Mineral-surfaced roll roofing shall be installed in accordance with this chapter and the manufacturer’s instructions.
Slate shingles.
The installation of slate shingles shall comply with the provisions of this section.
Deck requirements.
Slate shingles shall be fastened to solidly sheathed roofs.
Deck slope.
Slate shingles shall be used only on slopes of 4 units vertical in 12 units horizontal (33-percent slope) or greater.
Underlayment.
Underlayment shall comply with Section R905.1.1.
Ice barrier.
Where required, ice barriers shall comply with Section R905.1.2.
Material standards.
Slate shingles shall comply with ASTM C406.
Application.
Minimum headlap for slate shingles shall be in accordance with Table R905.6.5. Slate shingles shall be secured to the roof with two fasteners per slate.
Flashing.
Flashing and counterflashing shall be made with sheet metal. Valley flashing shall be not less than 15 inches (381 mm) wide.
Metal Roof Panels
Section R905.7 — Metal Roof Panels. Metal roof panel coverings shall be installed on roof slopes of 3 units vertical in 12 units horizontal (3:12) or greater unless the panel system is designed and tested for lower s...
Deck requirements.
Wood shingles shall be installed on solid or spaced sheathing. Where spaced sheathing is used, sheathing boards shall be not less than 1-inch by 4-inch (25 mm by 102 mm) nominal dimensions and shall be spaced on centers equal to the weather exposure to coincide with the placement of fasteners.
Solid sheathing required.
In areas where the average daily temperature in January is 25°F (-4°C) or less, solid sheathing is required on that portion of the roof requiring the application of an ice barrier.
Deck slope.
Wood shingles shall be installed on slopes of 3 units vertical in 12 units horizontal (25-percent slope) or greater.
Underlayment.
Underlayment shall comply with Section R905.1.1.
Ice barrier.
Where required, ice barriers shall comply with Section R905.1.2.
Material standards.
INSIGHTS Wood shingles shall be of naturally durable wood and comply with the requirements of Table R905.7.4. INSIGHTS (1) TABLE R905.7.4 WOOD SHINGLE MATERIAL REQUIREMENTS MATERIAL MINIMUM GRADES APPLICABLE GRADING RULES Wood shingles of naturally durable wood 1, 2 or 3 CSSB
Application.
INSIGHTS Wood shingles shall be installed in accordance with this chapter and the manufacturer’s instructions. Wood shingles shall be laid with a side lap not less than 11/2 inches (38 mm) between joints in courses, and two joints shall not be in direct alignment in any three adjacent courses.
Valley flashing.
Roof flashing shall be not less than No.
Label required.
Each bundle of shingles shall be identified by a label of an approved grading or inspection bureau or agency.
Wood Shingles
Section R905.8 — Wood Shingles. Wood shingles shall be installed on roof slopes of 3 units vertical in 12 units horizontal (3:12) or greater. Shingles shall be No. 1 grade as defined in Table R905.8. Weather expo...
Deck requirements.
Wood shakes shall be used only on solid or spaced sheathing. Where spaced sheathing is used, sheathing boards shall be not less than 1-inch by 4-inch (25 mm by 102 mm) nominal dimensions and shall be spaced on centers equal to the weather exposure to coincide with the placement of fasteners.
Solid sheathing required.
In areas where the average daily temperature in January is 25°F (-4°C) or less, solid sheathing is required on that portion of the roof requiring an ice barrier.
Deck slope.
Wood shakes shall only be used on slopes of 3 units vertical in 12 units horizontal (25-percent slope) or greater.
Underlayment.
Underlayment shall comply with Section R905.1.1.
Ice barrier.
Where required, ice barriers shall comply with Section R905.1.2.
Interlayment.
Interlayment shall comply with ASTM D226, Type I.
Material standards.
Wood shakes shall comply with the requirements of Table R905.8.5.
Application.
INSIGHTS Wood shakes shall be installed in accordance with this chapter and the manufacturer’s installation instructions. Wood shakes shall be laid with a side lap not less than 11/2 inches (38 mm) between joints in adjacent courses.
Shake placement.
The starter course at the eaves shall be doubled and the bottom layer shall be either 15-inch (381 mm), 18-inch (457 mm) or 24-inch (610 mm) wood shakes or wood shingles. Fifteen-inch (381 mm) or 18-inch (457 mm) wood shakes shall be permitted to be used for the final course at the ridge.
Valley flashing.
Roof valley flashing shall be not less than No. 26 gage [0.019 inch (0.5 mm)] corrosion-resistant sheet metal and shall extend not less than 11 inches (279 mm) from the centerline each way.
Label required.
Each bundle of shakes shall be identified by a label of an approved grading or inspection bureau or agency.
Built-Up Roofing
Section R905.9 — Built-Up Roofing. Built-up roofing shall be installed on roof slopes of 1/4 unit vertical in 12 units horizontal (1/4:12) or greater. Built-up roofs shall consist of not less than three plies of app...
Slope.
Built-up roofs shall have a design slope of not less than 1/4 unit vertical in 12 units horizontal (2-percent slope) for drainage, except for coal-tar built-up roofs, which shall have a design slope of a minimum 1/8 unit vertical in 12 units horizontal (1-percent slope).
Material standards.
Built-up roof covering materials shall comply with the standards in Table R905.9.2 or UL 55A.
Application.
Built-up roofs shall be installed in accordance with this chapter and the manufacturer’s instructions.
Canales and Scuppers (NM Amendment)
NM-specific requirement for canales (traditional Southwestern roof drain spouts projecting through parapet walls). Metal pan lining required extending 6 inches minimum past inside of parapet, sealed to prevent moisture infiltration. Canales must be adequately sized for roof area.
Roof Ventilation
Roof ventilation ratio: 1:150 net free area to attic floor area, with exceptions for balanced intake/exhaust.
Material standards.
Above-deck thermal insulation board shall comply with the standards in Table R906.2.
Rooftop-mounted photovoltaic panel systems.
Rooftop-mounted photovoltaic panel systems shall be designed and installed in accordance with Section R324 and NFPA 70. SECTION R908 REROOFING
Reroofing
Parent section governing work on existing roofs.
General Re-Roofing
Section R908.1 — General Re-Roofing. Materials and methods of application used for re-covering or replacing an existing roof covering shall comply with Chapter 9. Not more than one re-cover is permitted over an existi...
Structural and construction loads.
The structural roof components shall be capable of supporting the roof covering system and the material and equipment loads that will be encountered during installation of the roof covering system.
Recovering Versus Replacement
Section R908.3 — Recovering Versus Replacement. New roof coverings shall not be installed without first removing existing roof coverings where the existing roof has two or more applications of any type of roof covering, where co...
Roof recover.
The installation of a new roof covering over an existing roof covering shall be permitted where any of the following conditions occur: 1. Where the new roof covering is installed in accordance with the roof covering manufacturer’s approved instructions 2.
Roof recover not allowed.
INSIGHTS A roof recover shall not be permitted where any of the following conditions occur: 1. Where the existing roof or roof covering is water soaked or has deteriorated to the point that the existing roof or roof covering is not adequate as a base for additional roofing.
Roof Recovering
RECOVERING OVER SHAKES - Must cover with gypsum/mineral fiber if creating concealed space.
Reinstallation of materials.
INSIGHTS Existing slate, clay or cement tile shall be permitted for reinstallation, except that damaged, cracked or broken slate or tile shall not be reinstalled.
Flashings
FLASHING RECONSTRUCTION - Per manufacturer instructions. Prime metal before bitumen adhesion.