RESIDENTIAL ROOFING & RE-ROOFING, ROOF
VENTILATION AND ROOF SHEATHING REQUIREMENTS MICHIGAN RESIDENTIAL CODE 2000
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.
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 only be used on roof slopes of two units vertical in 12 units horizontal (2:12) or greater. For roof slopes from two units vertical in 12 units horizontal (2:12) up to four units vertical in 12 units horizontal (4:12), double underlayment application is required in accordance with Section R905.2.7.
R905.2.3 Underlayment. Unless otherwise noted, required underlayment shall conform with ASTM D 226, Type 1, or ASTM D 4869, Type 1. Self adhering polymer modified bitumen sheet shall comply with ASTM D 1970
R905.2.4 Asphalt shingles. Asphalt shingles shall have self seal strips or be interlocking, and comply with ASTM D 225 or D 3462.
R905.2.5 Fasteners. Fasteners for asphalt shingles shall be galvanized steel, stainless steel, aluminum or copper roof mg nails, minimum 12 gage [0.105 inch (2.67 mm)] shank with a minimum ¾ inch (9.5 mm) diameter head, ASTM F 1667, of a length to penetrate through the roofing materials and a minimum of 3/4 inch (1.9.1 mm) into the roof sheathing. Where the roof sheathing is less than ¾ inch (19.1 mm) thick, the fasteners shall penetrate through the sheathing. Fasteners shall comply with ASTM F 1.667.
R905.2.6 Attachment. Asphalt shingles shall have the minimum number of fasteners required by the manufacturer. For normal application, asphalt shingles shall be secured to the roof with not less than four fasteners per strip shingle or two fasteners per individual shingle. Where the roof slope exceeds 20 units vertical in 12 units horizontal (20:12), special. methods of fastening are required.
Exception: Asphalt strip shingles shall have a minimum of six fasteners per shingle where the roof is in one of the following categories:
1. The basic wind speed per Figure R301 .2(4) is 110 miles per hour (177 km/h) or greater and the eave is 20 feet (6096 mm) or higher above grade.
2. The basic wind speed per Figure R30 1.2(4) is 120 miles per hour (193 km/h) or greaten
3. Special wind zones per Figure R301.2(4).
R905.2.7 Underlayment application. For roof slopes from two units vertical in 12 units horizontal (17 percent slope), up to four units vertical in 12 units horizontal (33 percent slope), underlayment shall be two layers applied in the following manner. Apply a 19 inch (483 mm) strip of underlayment felt parallel with and starting at the eaves, fastened sufficiently to hold in place. Starting at the eave, apply 36 inch wide (914 mm) sheets of underlayment, overlapping successive sheets 19 inches (483 mm), and fastened sufficiently to hold in place. For roof slopes of four units vertical in 12 units horizontal (33 percent slope) or greater, underlayment shall. be one layer applied in the following manner Underlayment shall be applied shingle fashion, parallel to and starting from the eave and lapped 2 inches (51 mm), fastened sufficiently to hold in place. End laps shall be offset by 6 feet (1829 mm).
R905.2.7.1 Ice protection. In areas where the average daily temperature in January is 25ºF (40C) or less, an ice barrier that consists of at least two layers of underlayment cemented together or of a self adhering polymer modified bitumen sheet, shall he used in lieu of normal underlayment and extend from the eave's edge to a point at least 24 inches (610 mm) inside the exterior wall line of the building.
R905.2.7.2 Underlayment and high wind. Underlayment applied in areas subject to high winds [greater than 110 mph (177 km/h) per Figure R301 .2(4)] shall be applied
instructions. Fasteners are to be applied along the overlap not farther apart than 36 inches (914 mm) on center.
R905.2.8 Flashing. Flashing for asphalt shingles shall comply with this section.
R905.2.8.1 Base and cap flashing. Base and cap flashing shall he installed in accordance with manufacturer’s installation instructions. Base flashing shall be of either corrosion resistant metal of minimum nominal 0.019 inch (0.483 mm) thickness or mineral surface roll roofing weighing a minimum of 77 pounds per 100 square feet (3.76 kg/m2). Cap flashing shall be corrosion resistant metal of minimum nominal 0.019 inch (0.483 mm) thickness.
R905.2.8.2 Valleys. Valley linings shall be installed in accordance with manufacturer's installation instructions before applying shingles. Valley linings of the following types shall be permitted:
1. For open valley (valley lining exposed) lined with metal, the valley lining shall be at least 24 inches (610 mm) wide and of any of the corrosion resistant metals in Table R905.2.1.2.
2. For open valleys, valley lining of two plies of mineral surface roll roofing, complying with ASTM P 249, shall be permitted. The bottom layer shall be 19 inches (457 mm) and the top layer a minimum of 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 D224 Type II or Type III and at least 36 inches (914 mm) wide or valley lining as described in Items 1 and 2 above shall be permitted. Specialty underlayment complying with ASTM D 1970 may be used in lieu of tie lining material.
R905.2.8.3 Crickets and saddles. A cricket or saddle shall be installed on the ridge side of any chimney greater than 30 inches (762 mm) wide. Cricket or saddle coverings shall be sheet metal or of the same material as the roof covering.
R905.2.8.4 Sidewall flashing. Flashing against a vertical sidewall shall be by the step flashing method.
R905.2.8.5 Other flashing. Flashing against a vertical front wall, as well as soil stack, vent pipe and chimney flashing, shall be applied according to asphalt shingle manufacturer's printed instructions.
SECTION R9O7 RE-ROOFING
R907.1 General. Materials and methods of application used for recovering or replacing an existing roof covering shall comply with the requirements of this chapter. Roof repairs to existing roofs and roof coverings shall comply with the provisions of Chapter 34 of the International Building Code, but more than 25 percent of the roof covering of any building shall not be removed and replaced within a 2 month period unless the entire roof covering is made to conform to the requirements for new roofing.
Exception: Re-roofing shall not be required to meet the minimum design slope requirement of one-fourth vertical in 12 units horizontal (2 percent slope) in Section R905 for roofs that provide positive roof drainage.
R907.2 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.
R907.3 Recovering versus replacement. New roof coverings shall not be installed without first removing existing roof coverings 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 wood shake, slate, clay, cement or asbestos cement tile.
3. Where the existing roof has two or more applications of any type of roof covering.
4. For asphalt shingles, when the building is located in an area subject to severe hail damage according to Figure R907.3.
Exceptions:
1. 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 that do not rely on existing roofs and roof coverings for support shall not require the removal of existing roof coverings.
2. Metal panel, metal shingle, and concrete and clay tile roof coverings shall be permitted to be installed over existing wood shake roofs when applied in accordance with Section R907.4.
R907.4 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.
R907.5 Reinstallation of materials. Existing slate, clay or cement tile shall be permitted for reinstallation, except that dam aged, cracked or broken slate or tile shall not be reinstalled.
Existing vent flashing, metal edgings, drain outlets, collars and metal counter flashings shall not be reinstalled where rusted, damaged or deteriorated. Aggregate surfacing materials shall not be reinstalled.
R907.6 Flashings. Flashings shall be reconstructed in accordance with approved manufacturer's installation instructions. Metal flashing to which bituminous materials are robe adhered shall be primed prior to installation.
SECTION R803 ROOF SHEATHING
R803.1 Lumber sheathing. Allowable spans for lumber used as roof sheathing shall conform to Table R803.1. Spaced lumber sheathing for wood shingle and shake roofing shall conform to the requirements of Sections R905.7 and R905.8. Spaced lumber sheathing is not allowed in Seismic Design Category D2 R803.2 Wood structural panel sheathing.
R803.2.1 Identification and grade.
Wood structural panels shall conform to DOC PS 1, DOC PS 2 or, when
manufactured in Canada, CSA 0437, and shall be identified by grade mark or certificate of inspection issued by an approved agency. Wood structural panels shall comply with the grades specified in Table R503.2.1.1(1).
R803.2.1.1 Exposure durability. All wood structural panels, when designed to be permanently exposed in outdoor applications, shall be of an exterior exposure durability. Wood structural panel roof sheathing exposed to the underside maybe of interior type bonded with exterior glue, identified as Exposure 1.
R803.2.1.2 Fire retardant treated plywood. The allowable unit stresses for fire retardant treated plywood, including fastener values, shall he developed from an approved method of investigation that considers the effects of anticipated temperature and humidity to which the fire retardant treated plywood will be subjected, the type of treatment and redrying process. The fire retardant treated plywood shall be graded by an approved agency.
R803.2.2 Allowable spans. The maximum allowable spans for wood structural panel roof sheathing shall not exceed the values set forth in Table R503.2.1.1(1).
R803.2.3 Installation. Wood structural panel used as roof sheathing shall be installed with joints staggered or nonstaggered in accordance with Table R602.3(1), or APA E3O for wood roof framing or with Table k804.3 for steel roof framing.
SECTION R806 ROOF VENTILATION
R806.1 Ventilation required. Enclosed attics and enclosed rafter spaces formed where ceilings are applied directly to the underside of roof rafters shall have cross ventilation for each separate space by ventilating openings protected against the en trance of rain or snow. Ventilating openings shall be provided with corrosion resistant wire mesh, with 1/8 inch (3.2 mm) minimum to 1/4 inch (6.35 mm) maximum openings.
R806.2 Minimum area. The total net free ventilating area shall not be less than 1 to 150 of the area of the space ventilated except that the total area is permitted to be reduced to 1 to 300, provided at least 50 percent and not more than 80 percent of the required ventilating area is provided by ventilators located in the upper portion of the space to be ventilated at least 3 feet (914 mm) above eave or cornice vents with the balance of the required ventilation provided by eave or cornice vents. As an alternative, the net free cross ventilation area may be reduced to 1 to 300 when a vapor barrier having a transmission rate not exceeding 1 perm (57.4 mg/s·m2·Pa) is installed on the warm side of the ceiling.
R806.3 Vent clearance. Where eave or cornice vents arc in stalled, insulation shall not block the free flow of air. A minimum of a 1 inch (25.4 mm) space shall be provided between the insulation and the roof sheathing at the location of the vent.
Two inspections are required for a strip and re-roof. The first is an open roof inspection after the shingles have been removed and all bad wood replaced. With Department permission you may take photographs of the open roof in lieu of the inspection and provide them at the time of the final. The pictures must clearly identify the structure being worked on (I.E., a shot from the front showing the address). A final is required for all permits. You must provide an OSHA approved ladder, or alternate access to the roof, for the inspection.
