CHAPTER 9
ROOF ASSEMBLIES
SECTION R901
GENERAL
R901.1 Scope.
The provisions of this chapter shall govern the design, materials, construction and quality of roof assemblies.
SECTION R902
FIRE CLASSIFICATION
R902.1 Roof covering materials.
Roofs shall be covered with materials as set forth in Sections R904 and R905. Class A, B or C roofing shall be installed in jurisdictions designated by law as requiring their use or where the edge of the roof is less than 3 feet (914 mm) from a lot line. Class A, B and C roofing required by this section to be listed shall be tested in accordance with ASTM E108 or UL 790.
Exceptions:
1.Class A roof assemblies include those with coverings of brick, masonry and exposed concrete roof deck.
2.Class A roof assemblies include ferrous or copper shingles or sheets, metal sheets and shingles, clay or concrete roof tile, or slate installed on noncombustible decks.
3.Class A roof assemblies include minimum 16 ounces per square foot (4.882 kg/m2) copper sheets installed over combustible decks.
4.Class A roof assemblies include slate installed over underlayment over combustible decks.
R902.2 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. Each bundle shall be marked to identify the manufactured unit and the manufacturer, and shall be labeled to identify the classification of the material in accordance with the testing required in Section R902.1, the treating company and the quality control agency.
R902.3 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.
R902.4 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. Class A, B or C photovoltaic panel systems and modules shall be installed in jurisdictions designated by law as requiring their use or where the edge of the roof is less than 3 feet (914 mm) from a lot line.
SECTION R903
WEATHER PROTECTION
R903.1 General.
Roof decks shall be covered with approved roof coverings secured to the building or structure in accordance with the provisions of this chapter. Roof assemblies shall be designed and installed in accordance with this code and the approved manufacturer’s instructions such that the roof assembly shall serve to protect the building or structure.
R903.2 Flashing.
Flashings shall be installed in a manner that prevents moisture from entering the wall and roof through joints in copings, through moisture permeable materials and at intersections with parapet walls and other penetrations through the roof plane.
R903.2.1 Locations.
Flashings shall be installed at wall and roof intersections, wherever there is a change in roof slope or direction and around roof openings. A flashing shall be installed to divert the water away from where the eave of a sloped roof intersects a vertical sidewall. Where flashing is of metal, the metal shall be corrosion resistant with a thickness of not less than 0.019 inch (0.5 mm) (No. 26 galvanized sheet).
R903.2.2 Crickets and saddles.
A cricket or saddle shall be installed on the ridge side of any chimney or penetration more than 30 inches (762 mm) wide as measured perpendicular to the slope. Cricket or saddle coverings shall be sheet metal or of the same material as the roof covering.
R903.3 Coping.
Parapet walls shall be properly coped with noncombustible, weatherproof materials of a width not less than the thickness of the parapet wall.
R903.4 Roof drainage.
Unless roofs are sloped to drain over roof edges, roof drains shall be installed at each low point of the roof.
R903.4.1 Secondary (emergency overflow) drains or scuppers.
Where roof drains are required, secondary emergency overflow roof drains or scuppers shall be provided where the roof perimeter construction extends above the roof in such a manner that water will be entrapped if the primary drains allow buildup for any reason. Overflow drains having the same size as the roof drains shall be installed with the inlet flow line located 2 inches (51 mm) above the low point of the roof, or overflow scuppers having three times the size of the roof drains and having a minimum opening height of 4 inches (102 mm) shall be installed in the adjacent parapet walls with the inlet flow located 2 inches (51 mm) above the low point of the roof served. The installation and sizing of overflow drains, leaders and conductors shall comply with Sections 1106 and 1108 of the South Carolina Plumbing Code, as applicable.
Overflow drains shall discharge to an approved location and shall not be connected to roof drain lines.
SECTION R904
MATERIALS
R904.1 Scope.
The requirements set forth in this section shall apply to the application of roof covering materials specified herein. Roof assemblies shall be applied in accordance with this chapter and the manufacturer’s installation instructions. Installation of roof assemblies shall comply with the applicable provisions of Section R905.
R904.2 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.
R904.3 Material specifications and physical characteristics.
Roof covering materials shall conform to the applicable standards listed in this chapter.
R904.4 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.
SECTION R905
REQUIREMENTS FOR ROOF COVERINGS
R905.1 Roof covering application.
Roof coverings shall be applied in accordance with the applicable provisions of this section and the manufacturer’s installation instructions. Unless otherwise specified in this section, roof coverings shall be installed to resist the component and cladding loads specified in Table R301.2.1(1), adjusted for height and exposure in accordance with Table R301.2.1(2).
R905.1.1 Underlayment.
Underlayment for asphalt shingles, clay and concrete tile, metal roof shingles, mineral-surfaced roll roofing, slate and slate-type shingles, wood shingles, wood shakes, metal roof panels and photovoltaic shingles shall conform to the applicable standards listed in this chapter. Underlayment materials required to comply with ASTM D226, D1970, D4869 and D6757 shall bear a label indicating compliance to the standard designation and, if applicable, type classification indicated in Table R905.1.1(1). Underlayment shall be applied in accordance with Table R905.1.1(2). Underlayment shall be attached in accordance with Table R905.1.1(3).
Exceptions:
1. As an alternative, self-adhering polymer-modified bitumen underlayment bearing a label indicating compliance with ASTM D1970 and installed in accordance with both the underlayment manufacturer’s and roof covering manufacturer’s instructions for the deck material, roof ventilation configuration and climate exposure for the roof covering to be installed, shall be permitted.
2. As an alternative, a minimum 4-inch-wide (102 mm) strip of self-adhering polymer-modified bitumen membrane bearing a label indicating compliance with ASTM D1970, installed in accordance with the manufacturer’s installation instructions for the deck material, shall be applied over all joints in the roof decking. An approved underlayment complying with Table R905.1.1(1) for the applicable roof covering for areas where wind design is not required in accordance with Figure R301.2.1.1 shall be applied over the entire roof over the 4-inch wide (102 mm) membrane strips. Underlayment shall be applied in accordance with Table R905.1.1(2) using the application requirements for areas where wind design is not required in accordance with Figure R301.2.1.1. Underlayment shall be attached in accordance withTable R905.1.1(3).➡
TABLE R905.1.1(1)
UNDERLAYMENT TYPES
For SI: 1 mile per hour = 0.447 m/s.
TABLE R905.1.1(2)
UNDERLAYMENT APPLICATION
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 mile per hour = 0.447 m/s.
TABLE R905.1.1(3)
UNDERLAYMENT APPLICATION
For SI: 1 inch = 25.4 mm, 1 mile per hour = 0.447 m/s.
R905.1.2 Ice barriers.
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 shall be installed for asphalt shingles, metal roof shingles, mineral-surfaced roll roofing, slate and slate-type shingles, wood shingles and wood shakes. The ice barrier shall consist of not fewer than two layers of underlayment cemented together, or a self-adhering polymer-modified bitumen sheet shall be used in place of normal underlayment and extend from the lowest edges of all roof surfaces to a point not less than 24 inches (610 mm) inside the exterior wall line of the building. On roofs with slope equal to or greater than 8 units vertical in 12 units horizontal (67-percent slope), the ice barrier shall also be applied not less than 36 inches (914 mm) measured along the roof slope from the eave edge of the building.
Exception: Detached accessory structures not containing conditioned floor area.
R905.2 Asphalt shingles.
The installation of asphalt shingles shall comply with the provisions of this section.
R905.2.1 Sheathing requirements.
Asphalt shingles shall be fastened to solidly sheathed decks.
R905.2.2 Slope.
Asphalt shingles shall be used only on roof slopes of 2 units vertical in 12 units horizontal (17-percent slope) or greater. For roof slopes from 2 units vertical in 12 units horizontal (17-percent slope) up to 4 units vertical in 12 units horizontal (33-percent slope), double underlayment application is required in accordance with Section R905.1.1.
R905.2.4.1 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. Asphalt shingle packaging shall bear a label to indicate compliance with ASTM D7158 and the required classification in Table R905.2.4.1.
TABLE R905.2.4.1
CLASSIFICATION OF ASPHALT ROOF SHINGLES
R905.2.5 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 3/4 inch (19.1 mm) into the roof sheathing. Where the roof sheathing is less than 3/4 inch (19.1 mm) thick, the fasteners shall penetrate through the sheathing.
R905.2.6 Attachment.
Asphalt shingles shall have the minimum number of fasteners required by the manufacturer’s approved installation instructions, but not less than four fasteners per strip shingle or two fasteners per individual shingle. Where the roof slope exceeds 21 units vertical in 12 units horizontal (21:12, 175-percent slope), shingles shall be installed in accordance with the manufacturer’s approved installation instructions.
R905.2.8 Flashing.
Flashing for asphalt shingles shall comply with this section and the asphalt shingle manufacturer’s approved installation instructions.
R905.2.8.1 Base and cap flashing.
Base and cap flashing shall be installed in accordance with manufacturer’s instructions. Base flashing shall be of either corrosion-resistant metal of minimum nominal 0.019-inch (0.5 mm) thickness or mineral-surfaced roll roofing weighing not less than 77 pounds per 100 square feet (4 kg/m2). Cap flashing shall be corrosion-resistant metal of minimum nominal 0.019-inch (0.5 mm) thickness.
R905.2.8.2 Valleys.
Valley linings shall be installed in accordance with the manufacturer’s instructions before applying shingles. Valley linings of the following types shall be permitted:
1.For open valleys (valley lining exposed) lined with metal, the valley lining shall be not less than 24 inches (610 mm) wide and of any of the corrosion-resistant metals in Table R905.2.8.2.
2.For open valleys, valley lining of two plies of mineral-surfaced roll roofing, complying with ASTM D3909 or ASTM D6380 Class M, shall be permitted. The bottom layer shall be 18 inches (457 mm) and the top layer not less than 36 inches (914 mm) wide.
3.For closed valleys (valley covered with shingles), valley lining of one ply of smooth roll roofing complying with ASTM D6380 and not less than 36 inches wide (914 mm) or valley lining as described in Item 1 or 2 shall be permitted. Self-adhering polymer-modified bitumen underlayment complying with ASTM D1970 shall be permitted in lieu of the lining material.
TABLE R905.2.8.2
VALLEY LINING MATERIAL
For SI: 1 inch = 25.4 mm, 1 pound = 0.454 kg, 1 square foot = 0.93 m2.
R905.2.8.3 Sidewall flashing.
Base flashing against a vertical sidewall shall be continuous or step flashing and shall be not less than 4 inches (102 mm) in height and 4 inches (102 mm) in width and shall direct water away from the vertical sidewall onto the roof or into the gutter. Where siding is provided on the vertical sidewall, the vertical leg of the flashing shall be continuous under the siding. Where anchored masonry veneer is provided on the vertical sidewall, the base flashing shall be provided in accordance with this section and counterflashing shall be provided in accordance with Section R703.8.2.2. Where exterior plaster or adhered masonry veneer is provided on the vertical sidewall, the base flashing shall be provided in accordance with this section and Section R703.6.3.
R905.2.8.4 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.
R905.2.8.5 Drip edge.
A drip edge shall be provided at eaves and rake edges of asphalt shingle roofs where required by the manufacturer.
R905.3 Clay and concrete tile.
The installation of clay and concrete tile shall comply with the provisions of this section.
R905.3.2 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. For roof slopes from 21/2 units vertical in 12 units horizontal (25-percent slope) to 4 units vertical in 12 units horizontal (33-percent slope), double underlayment application is required in accordance with Section R905.3.3.
R905.3.6 Fasteners.
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. Attaching wire for clay or concrete tile shall not be smaller than 0.083 inch (2 mm). Perimeter fastening areas include three tile courses but not less than 36 inches (914 mm) from either side of hips or ridges and edges of eaves and gable rakes.
R905.3.7 Application.
Tile shall be applied in accordance with this chapter and the manufacturer’s installation instructions, based on the following:
1.Climatic conditions.
2.Roof slope.
3.Underlayment system.
4.Type of tile being installed.
Clay and concrete roof tiles shall be fastened in accordance with this section and the manufacturer’s installation instructions. Perimeter tiles shall be fastened with not less than one fastener per tile. Tiles with installed weight less than 9 pounds per square foot (0.4 kg/m2) require not less than one fastener per tile regardless of roof slope. Clay and concrete roof tile attachment shall be in accordance with the manufacturer’s installation instructions where applied in areas where the ultimate design wind speed exceeds 130 miles per hour (58 m/s) and on buildings where the roof is located more than 40 feet (12 192 mm) above grade. In areas subject to snow, not less than two fasteners per tile are required. In other areas, clay and concrete roof tiles shall be attached in accordance with Table R905.3.7.
TABLE R905.3.7
CLAY AND CONCRETE TILE ATTACHMENT
| SHEATHING | ROOF SLOPE | NUMBER OF FASTENERS |
| Solid without battens | All | One per tile |
| Spaced or solid with battens and slope < 5:12 | Fasteners not required | — |
| Spaced sheathing without battens | 5:12 ≤ slope < 12:12 | One per tile/every other row |
| 12:12 ≤ slope < 24:12 | One per tile |
R905.3.8 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. The valley flashing shall extend not less than 11 inches (279 mm) from the centerline each way and have a splash diverter rib not less than 1 inch (25 mm) in height at the flow line formed as part of the flashing. Sections of flashing shall have an end lap of not less than 4 inches (102 mm). For roof slopes of 3 units vertical in 12 units horizontal (25-percent slope) and greater, valley flashing shall have a 36-inch-wide (914 mm) underlayment of one layer of Type I underlayment running the full length of the valley, in addition to other required underlayment. In areas where the average daily temperature in January is 25°F (-4°C) or less, metal valley flashing underlayment shall be solid-cemented to the roofing underlayment for slopes less than 7 units vertical in 12 units horizontal (58-percent slope) or be of self-adhering polymer-modified bitumen sheet.
R905.4 Metal roof shingles.
The installation of metal roof shingles shall comply with the provisions of this section.
R905.4.1 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.
R905.4.2 Deck slope.
Metal roof shingles shall not be installed on roof slopes below 3 units vertical in 12 units horizontal (25-percent slope).
R905.4.4 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).
R905.4.4.1 Wind resistance of metal roof shingles.
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. Metal roof shingles tested in accordance with ASTM D3161 shall meet the classification requirements of Table R905.4.4.1 for the appropriate maximum basic wind speed and the metal shingle packaging shall bear a label to indicate compliance with ASTM D3161 and the required classification in Table R905.2.4.1.
TABLE R905.4.4.1
CLASSIFICATION OF STEEP SLOPE METAL ROOF SHINGLES TESTED IN ACCORDANCE WITH ASTM D3161
For SI: 1 mile per hour = 1.609 kph.
R905.4.5 Application.
Metal roof shingles shall be secured to the roof in accordance with this chapter and the approved manufacturer’s installation instructions.
R905.4.6 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). The valley flashing shall extend not less than 8 inches (203 mm) from the centerline each way and shall have a splash diverter rib not less than 3/4 inch (19 mm) in height at the flow line formed as part of the flashing. Sections of flashing shall have an end lap of not less than 4 inches (102 mm). The metal valley flashing shall have a 36-inch-wide (914 mm) underlayment directly under it consisting of one layer of underlayment running the full length of the valley, in addition to underlayment required for metal roof shingles. In areas where the average daily temperature in January is 25°F (-4°C) or less, the metal valley flashing underlayment shall be solid-cemented to the roofing underlayment for roof slopes under 7 units vertical in 12 units horizontal (58-percent slope) or self-adhering polymer-modified bitumen sheet.
R905.5 Mineral-surfaced roll roofing.
The installation of mineral-surfaced roll roofing shall comply with this section.
R905.5.1 Deck requirements.
Mineral-surfaced roll roofing shall be fastened to solidly sheathed roofs.
R905.5.2 Deck slope.
Mineral-surfaced roll roofing shall not be applied on roof slopes below 1 unit vertical in 12 units horizontal (8-percent slope).
R905.5.5 Application.
Mineral-surfaced roll roofing shall be installed in accordance with this chapter and the manufacturer’s instructions.
R905.6 Slate shingles.
The installation of slate shingles shall comply with the provisions of this section.
R905.6.1 Deck requirements.
Slate shingles shall be fastened to solidly sheathed roofs.
R905.6.2 Deck slope.
Slate shingles shall be used only on slopes of 4 units vertical in 12 units horizontal (33-percent slope) or greater.
R905.6.5 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. Slate shingles shall be installed in accordance with this chapter and the manufacturer’s instructions.
TABLE R905.6.5
SLATE SHINGLE HEADLAP
| SLOPE | HEADLAP (inches) |
| 4:12 ≤ slope < 8:12 | 4 |
| 8:12 ≤ slope < 20:12 | 3 |
| Slope ≥ 20:12 | 2 |
For SI: 1 inch = 25.4 mm.
R905.6.6 Flashing.
Flashing and counterflashing shall be made with sheet metal. Valley flashing shall be not less than 15 inches (381 mm) wide. Valley and flashing metal shall be a minimum uncoated thickness of 0.0179-inch (0.5 mm) zinc coated G90. Chimneys, stucco or brick walls shall have not less than two plies of felt for a cap flashing consisting of a 4-inch-wide (102 mm) strip of felt set in plastic cement and extending 1 inch (25 mm) above the first felt and a top coating of plastic cement. The felt shall extend 2 inches (51 mm) over the base flashing.
R905.7 Wood shingles.
The installation of wood shingles shall comply with the provisions of this section.
R905.7.1 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.
R905.7.1.1 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.
R905.7.2 Deck slope.
Wood shingles shall be installed on slopes of 3 units vertical in 12 units horizontal (25-percent slope) or greater.
R905.7.4 Material standards.
Wood shingles shall be of naturally durable wood and comply with the requirements of Table R905.7.4.
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 |
R905.7.5 Application.
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. Spacing between shingles shall be not less than 1/ 4 inch to 3/8 inch (6.4 mm to 9.5 mm). Weather exposure for wood shingles shall not exceed those set in Table R905.7.5(1). Fasteners for untreated (naturally durable) wood shingles shall be box nails in accordance with Table R905.7.5(2). Nails shall be stainless steel Type 304 or 316 or hot-dipped galvanized with a coating weight of ASTM A153 Class D (1.0 oz/ft2). Alternatively, two 16-gage stainless steel Type 304 or 316 staples with crown widths 7/16 inch (11.1 mm) minimum, 3/4 inch (19.1 mm) maximum, shall be used. Fasteners installed within 15 miles (24 km) of saltwater coastal areas shall be stainless steel Type 316. Fasteners for fire-retardant-treated shingles in accordance with Section R902 or pressure-impregnated-preservative-treated shingles of naturally durable wood in accordance with AWPA U1 shall be stainless steel Type 316. Fasteners shall have a minimum penetration into the sheathing of 3/4 inch (19.1 mm). For sheathing less than 3/4 inch in (19.1 mm) thickness, each fastener shall penetrate through the sheathing. Wood shingles shall be attached to the roof with two fasteners per shingle, positioned in accordance with the manufacturer’s installation instructions. Fastener packaging shall bear a label indicating the appropriate grade material or coating weight.
TABLE R905.7.5(1)
WEATHER EXPOSURE AND ROOF SLOPE
| ROOFING MATERIAL | LENGTH (inches) | GRADE | EXPOSURE (inches) | |
| 3:12 pitch to < 4:12 | 4:12 pitch or steeper | |||
| Shingles of naturally durable wood | 16 | No. 1 | 33/4 | 5 |
| No. 2 | 31/2 | 4 | ||
| No. 3 | 3 | 31/2 | ||
| 18 | No. 1 | 41/4 | 51/2 | |
| No. 2 | 4 | 41/2 | ||
| No. 3 | 31/2 | 4 | ||
| 24 | No. 1 | 53/4 | 71/2 | |
| No. 2 | 51/2 | 61/2 | ||
| No. 3 | 5 | 51/2 | ||
For SI: 1 inch = 25.4 mm.
TABLE R905.7.5(2)
NAIL REQUIREMENTS FOR WOOD SHAKES AND WOOD SHINGLES
| PRODUCT TYPE | NAIL TYPE, MINIMUM LENGTH AND SHANK DIAMETER (inches) |
| Shakes | |
| 18″ straight-split | 5d box 13/4″ × 0.080 |
| 18″ and 24″ handsplit and resawn | 6d box 2″ × 0.099 |
| 24″ taper-split | 5d box 13/4″ × 0.080 |
| 18″ and 24″ tapersawn | 6d box 2″ × 0.099 |
| Shingles | |
| 16″ and 18″ | 3d box 11/4″ × 0.076 |
| 24″ | 4d box 11/2″ × 0.076 |
For SI: 1 inch = 25.4 mm.
R905.7.6 Valley flashing.
Roof flashing shall be not less than No. 26 gage [0.019 inches (0.5 mm)] corrosion-resistant sheet metal and shall extend 10 inches (254 mm) from the centerline each way for roofs having slopes less than 12 units vertical in 12 units horizontal (100-percent slope), and 7 inches (178 mm) from the centerline each way for slopes of 12 units vertical in 12 units horizontal (100-percent slope) and greater. Sections of flashing shall have an end lap of not less than 4 inches (102 mm).
R905.7.7 Label required.
Each bundle of shingles shall be identified by a label of an approved grading or inspection bureau or agency.
R905.8 Wood shakes.
The installation of wood shakes shall comply with the provisions of this section.
R905.8.1 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. Where 1-inch by 4-inch (25 mm by 102 mm) spaced sheathing is installed at 10 inches (254 mm) on center, additional 1-inch by 4-inch (25 mm by 102 mm) boards shall be installed between the sheathing boards.
R905.8.1.1 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.
R905.8.2 Deck slope.
Wood shakes shall only be used on slopes of 3 units vertical in 12 units horizontal (25-percent slope) or greater.
TABLE R905.8.5
WOOD SHAKE MATERIAL REQUIREMENTS
R905.8.6 Application.
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. Spacing between shakes in the same course shall be 3/ 8 inch to 5/8 inch (9.5 mm to 15.9 mm) including tapersawn shakes. Weather exposures for wood shakes shall not exceed those set in Table R905.8.6. Fasteners for untreated (naturally durable) wood shakes shall be box nails in accordance with Table R905.7.5(2). Nails shall be stainless steel Type 304, or Type 316 or hot-dipped with a coating weight of ASTM A153 Class D (1.0 oz/ft2). Alternatively, two 16-gage Type 304 or Type 316 stainless steel staples, with crown widths 7/16 inch (11.1 mm) minimum, 3/4 inch (19.1 mm) maximum, shall be used. Fasteners installed within 15 miles (24 km) of saltwater coastal areas shall be stainless steel Type 316. Wood shakes shall be attached to the roof with two fasteners per shake positioned in accordance with the manufacturer’s installation instructions. Fasteners for fire-retardant-treated (as defined in Section R902) shakes or pressure-impregnated-preservative-treated shakes of naturally durable wood in accordance with AWPA U1 shall be stainless steel Type 316. Fasteners shall have a minimum penetration into the sheathing of 3/4 inch (19.1 mm). Where the sheathing is less than 3/4 inch (19.1 mm) thick, each fastener shall penetrate through the sheathing. Fastener packaging shall bear a label indicating the appropriate grade material or coating weight.
TABLE R905.8.6
WOOD SHAKE WEATHER EXPOSURE AND ROOF SLOPE
| ROOFING MATERIAL | LENGTH (inches) | GRADE | EXPOSURE (inches) |
| 4:12 pitch or steeper | |||
| Shakes of naturally durable wood | 18 | No. 1 | 71/2 |
| 24 | No. 1 | 10a | |
| Preservative-treated tapersawn shakes of Southern Yellow Pine | 18 | No. 1 | 71/2 |
| 24 | No. 1 | 10 | |
| 18 | No. 2 | 51/2 | |
| 24 | No. 2 | 71/2 | |
| Taper-sawn shakes of naturally durable wood | 18 | No. 1 | 71/2 |
| 24 | No. 1 | 10 | |
| 18 | No. 2 | 51/2 | |
| 24 | No. 2 | 71/2 |
For SI: 1 inch = 25.4 mm.
a.For 24-inch by 3/8-inch handsplit shakes, the maximum exposure is 71/2 inches.
R905.8.7 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. Shakes shall be interlaid with 18-inch-wide (457 mm) strips of not less than No. 30 felt shingled between each course in such a manner that felt is not exposed to the weather by positioning the lower edge of each felt strip above the butt end of the shake it covers a distance equal to twice the weather exposure.
R905.8.8 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. Sections of flashing shall have an end lap of not less than 4 inches (102 mm).
R905.8.9 Label required.
Each bundle of shakes shall be identified by a label of an approved grading or inspection bureau or agency.
R905.9 Built-up roofs.
The installation of built-up roofs shall comply with the provisions of this section and the manufacturer’s approved installation instructions.
R905.9.1 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).
R905.9.2 Material standards.
Built-up roof covering materials shall comply with the standards in Table R905.9.2 or UL 55A.
TABLE R905.9.2
BUILT-UP ROOFING MATERIAL STANDARDS
R905.9.3 Application.
Built-up roofs shall be installed in accordance with this chapter and the manufacturer’s instructions.
R905.10 Metal roof panels.
The installation of metal roof panels shall comply with the provisions of this section.
R905.10.1 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.
R905.10.2 Slope.
Minimum slopes for metal roof panels shall comply with the following:
1.The minimum slope for lapped, nonsoldered-seam metal roofs without applied lap sealant shall be 3 units vertical in 12 units horizontal (25-percent slope).
2.The minimum slope for lapped, nonsoldered-seam metal roofs with applied lap sealant shall be 1/2 unit vertical in 12 units horizontal (4-percent slope). Lap sealants shall be applied in accordance with the approved manufacturer’s installation instructions.
3.The minimum slope for standing-seam roof systems shall be 1/4 unit vertical in 12 units horizontal (2-percent slope).
R905.10.3 Material standards.
Metal-sheet roof covering systems that incorporate supporting structural members shall be designed in accordance with the South Carolina Building Code. Metal-sheet roof coverings installed over structural decking shall comply with Table R905.10.3(1). The materials used for metal-sheet roof coverings shall be naturally corrosion resistant or provided with corrosion resistance in accordance with the standards and minimum thicknesses shown in Table R905.10.3(2).
TABLE R905.10.3(1)
METAL ROOF COVERING STANDARDS
For SI: 1 ounce per square foot = 0.305 kg/m2, 1 pound per square foot = 4.214 kg/m2, 1 inch = 25.4 mm, 1 pound = 0.454 kg.
R905.10.4 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.Galvanized fasteners shall be used for steel roofs.
2.Copper, brass, bronze, copper alloy and 300-series stainless steel fasteners shall be used for copper roofs.
3.Stainless steel fasteners are acceptable for metal roofs.
R905.11 Modified bitumen roofing.
The installation of modified bitumen roofing shall comply with the provisions of this section and the manufacturer’s approved installation instructions.
R905.11.1 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.
R905.11.2 Material standards.
Modified bitumen roofing shall comply with the standards in Table R905.11.2.
R905.11.3 Application.
Modified bitumen roofs shall be installed in accordance with this chapter and the manufacturer’s instructions.
R905.12 Thermoset single-ply roofing.
The installation of thermoset single-ply roofing shall comply with the provisions of this section.
R905.12.1 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.
R905.12.3 Application.
Thermoset single-ply roofs shall be installed in accordance with this chapter and the manufacturer’s instructions.
R905.13 Thermoplastic single-ply roofing.
The installation of thermoplastic single-ply roofing shall comply with the provisions of this section.
R905.13.1 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).
R905.13.3 Application.
Thermoplastic single-ply roofs shall be installed in accordance with this chapter and the manufacturer’s instructions.
R905.14 Sprayed polyurethane foam roofing.
The installation of sprayed polyurethane foam roofing shall comply with the provisions of this section.
R905.14.1 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.
R905.14.3 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.
R905.15 Liquid-applied roofing.
The installation of liquid-applied roofing shall comply with the provisions of this section.
R905.15.1 Slope.
Liquid-applied roofing shall have a design slope of not less than 1/4 unit vertical in 12 units horizontal (2-percent slope).
R905.15.3 Application.
Liquid-applied roofing shall be installed in accordance with this chapter and the manufacturer’s installation instructions.
R905.16 Photovoltaic shingles.
The installation of photovoltaic shingles shall comply with the provisions of this section, Section R324 and NFPA 70.
R905.16.1 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.
R905.16.2 Deck slope.
Photovoltaic shingles shall be used only on roof slopes of 2 units vertical in 12 units horizontal (2:12) or greater.
R905.16.5 Attachment.
Photovoltaic shingles shall be attached in accordance with the manufacturer’s installation instructions.
R905.16.6 Wind resistance.
Photovoltaic shingles shall comply with the classification requirements of Table R905.16.6 for the appropriate maximum basic wind speed.
TABLE R905.16.6
CLASSIFICATION OF PHOTOVOLTAIC SHINGLES
For SI:1 mile per hour = 1.609 kph.
R905.17 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.
R905.17.1 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.
R905.17.2 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.
R905.17.4 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 normal underlayment and extend from the lowest edges of all roof surfaces to a point not less than 24 inches (610 mm) inside the exterior wall line of the building.
Exception: Detached accessory structures that do not contain conditioned floor area.
R905.17.6 Attachment.
BIPV roof panels shall be attached in accordance with the manufacturer’s installation instructions.
➡
SECTION R906
ROOF INSULATION
R906.2 Material standards.
Above-deck thermal insulation board shall comply with the standards in Table R906.2.
TABLE R906.2
MATERIAL STANDARDS FOR ROOF INSULATION
SECTION R907
ROOFTOP-MOUNTED
PHOTOVOLTAIC PANEL SYSTEMS
SECTION R908
REROOFING
R908.1 General.
Materials and methods of application used for recovering or replacing an existing roof covering shall comply with the requirements of Chapter 9.
Exceptions:
1.Reroofing shall not be required to meet the minimum design slope requirement of one-quarter unit vertical in 12 units horizontal (2-percent slope) in Section R905 for roofs that provide positive roof drainage.
2.For roofs that provide positive drainage, recovering or replacing an existing roof covering shall not require the secondary (emergency overflow) drains or scuppers of Section R903.4.1 to be added to an existing roof.
R908.2 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.
R908.3 Roof replacement.
Roof replacement shall include the removal of existing layers of roof coverings down to the roof deck.
R908.3.1 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.Complete and separate roofing systems, such as standing-seam metal roof systems, that are designed to transmit the roof loads directly to the building’s structural system and do not rely on existing roofs and roof coverings for support, shall not require the removal of existing roof coverings.
3.Metal panel, metal shingle and concrete and clay tile roof coverings shall be permitted to be installed over existing wood shake roofs where applied in accordance with Section R908.4.
4.The application of a new protective roof coating over an existing protective roof coating, metal roof panel, metal roof shingle, mineral surfaced roll roofing, built-up roof, modified bitumen roofing, thermoset and thermoplastic single-ply roofing and spray polyurethane foam roofing system shall be permitted without tear-off of existing roof coverings.
R908.3.1.1 Roof recover not allowed.
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.
2.Where the existing roof covering is slate, clay, cement or asbestos-cement tile.
3.Where the existing roof has two or more applications of any type of roof covering.
R908.4 Roof recovering.
Where the application of a new roof covering over wood shingle or shake roofs creates a combustible concealed space, the entire existing surface shall be covered with gypsum board, mineral fiber, glass fiber or other approved materials securely fastened in place.
R908.5 Reinstallation of materials.
Existing slate, clay or cement tile shall be permitted for reinstallation, except that damaged, cracked or broken slate or tile shall not be reinstalled. Any existing flashings, edgings, outlets, vents or similar devices that are a part of the assembly shall be replaced where rusted, damaged or deteriorated. Aggregate surfacing materials shall not be reinstalled.
R908.6 Flashings.
Flashings shall be reconstructed in accordance with approved manufacturer’s installation instructions. Metal flashing to which bituminous materials are to be adhered shall be primed prior to installation.