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.
Roofing Assembly Requirements - Maryland
Maryland requires Class A fire-rated roofing in all jurisdictions. Materials must pass ASTM E108 or UL 790 testing with highest rating.
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.
General (Decking)
DECKING - Roof decks must be covered with approved coverings per manufacturer instructions.
Flashing
FLASHINGS - Required at wall/roof intersections, gutters, slope changes, and openings. Min 26 gauge galvanized.
Locations
FLASHING LOCATIONS - Required at wall/roof intersections, slope changes, direction changes, and roof openings.
Crickets and Saddles
CRICKETS & SADDLES - Required on ridge side of chimneys/penetrations >30" wide.
Roof Flashing Requirements - Maryland
Roof flashing: 26 ga min at all intersections. Maryland requires step flashing at sidewall conditions.
Coping (NM-Specific)
NM-specific requirement for plastered parapets (common in Southwestern architecture). Requires seamless permeable waterproof cover capping entire parapet, extending 4 inches on wall side, properly lapping roof membranes. Expanded metal lath over cover before stucco/plaster. No penetrating fasteners on horizontal parapet surfaces.
Roof Drainage
ROOF DRAINAGE: Gutters and downspouts must direct water away from foundation. Minimum gutter slope: 1/16" per foot toward outlet. Downspout outlets should discharge 6 feet minimum from foundation or into proper drainage system. Secondary drainage/overflow required for flat roofs with parapets.
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 Application
Roof coverings must comply with both code provisions and manufacturer instructions.
Metal Roof Panels
Parent section for standing seam and other metal roof panel requirements.
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
UNDERLAYMENT - Required for slopes 2:12+. Must meet ASTM standards with compliant labeling.
Modified bitumen roofing.
The installation of modified bitumen roofing shall comply with the provisions of this section and the manufacturer’s approved installation instructions.
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
Ice barrier REQUIRED STATEWIDE in Pennsylvania. Ice barrier shall be self-adhering polymer-modified bitumen sheet or two cemented underlayment layers extending from eave edge to point not less than 24 inches inside exterior wall line. On slopes ≥8:12, ice barrier shall also extend 36 inches up the roof slope.
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.
The installation of sprayed polyurethane foam roofing shall comply with the provisions of this section.
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
Roof Covering Application - Maryland
Roofing installations require permit/inspection in Maryland. Must follow both code and manufacturer specs. Wind resistance per local design speeds.
Asphalt Shingles
ASPHALT SHINGLES: Minimum slope 2:12. LOW-SLOPE ROOFS (2:12 to 4:12) require double underlayment. Solid sheathing required (minimum 7/16" OSB or 1/2" plywood). Underlayment standards: ASTM D226 (felt), D4869 (synthetic), D6757 (synthetic high-temp), D1970 (self-adhering ice & water).
Sheathing Requirements
SOLID SHEATHING - Asphalt shingles require solid (not spaced) sheathing.
Slope
MINIMUM SLOPE - Asphalt shingles require minimum 2:12 slope.
Underlayment.
Underlayment shall comply with Section R905.1.1.
Asphalt Shingles - Underlayment
UNDERLAYMENT FOR SHINGLES - Single layer D226 or D4869 with 2" laps, OR D1970 self-adhering.
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...
Asphalt Shingle Fasteners
FASTENER REQUIREMENTS: 12-gauge minimum shank, 3/8" minimum head diameter. Must penetrate 3/4" into sheathing (or through if thinner). STANDARD: 4 nails per 3-tab or architectural shingle. HIGH-WIND AREAS (>110 mph): 6 nails per shingle per manufacturer high-wind instructions.
Application
SHINGLE FASTENING - Minimum 4 nails per strip, 2 per individual. High wind areas per manufacturer.
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).
Ice Barrier Underlayment - Maryland
Ice barrier required on all roofs, extending minimum 24 inches past exterior wall. Critical for Maryland's freeze-thaw climate.
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.
Asphalt Shingle Requirements - Maryland
Minimum 4 fasteners per strip shingle. Eastern Shore and coastal Maryland require high-wind installation methods (110+ mph zones).
Clay and concrete tile.
INSIGHTS The installation of clay and concrete tile shall comply with the provisions of this section. INSIGHTS (1)
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.
Wood shingles.
INSIGHTS The installation of wood shingles shall comply with the provisions of this section. INSIGHTS (1)
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 shakes.
INSIGHTS The installation of wood shakes shall comply with the provisions of this section. INSIGHTS (1)
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 roofs.
The installation of built-up roofs shall comply with the provisions of this section and the manufacturer’s approved installation instructions.
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 Covering Requirements - Birmingham
Birmingham adopts 2021 IRC roofing requirements. Wind speed 115 mph requires enhanced fastening. Historic districts require COA for roof work. Climate Zone 3A - no ice barrier required.
Roofing Requirements - Arkansas (AFPC 2021 Vol III)
AFPC 2021 Volume III (based on 2021 IRC) governs residential roofing. Climate Zone 3A with 115 mph wind speed and tornado risk. Ice barriers not required per code but recommended. Permit nuance: roofing may trigger inspection requirements even below $5,000 threshold.
General.
INSIGHTS Where above-deck thermal insulation is installed, such insulation shall be covered with an approved roof covering and shall comply with NFPA 276 or UL 1256. INSIGHTS (2)
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
Reroofing must comply with Chapter 9 requirements.
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
ROOF TEAR-OFF REQUIRED when: water-soaked, wood/slate/tile existing, or 2+ existing layers.
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 Recover and Replacement - Maryland
Roof tear-off required for damaged roofs or when 2+ layers exist. Historic districts may require material matching approval.
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.