Free Technical Information for Building Inspectors, Contractors and Consumers. Code and Manufacturer's Information Resource
ROOFING: What's the Code Say ?
The Residential building code requires asphalt shingles to be installed per the manufacture's installation instructions.
Typical Manufacturer's Installation Instructions for Residential Grade Laminated Asphalt Arch. Shingles:
I. ROOF DECK
These type shingles are for application to roof decks capable of receiving and retaining fasteners, and to inclines of not less than 2 in. per foot. For roofs having pitches 2 in. per foot to less than 4 in. per foot, refer to special instructions titled "Low Slope Application". Shingles must be applied properly.
NEW ROOF DECK CONSTRUCTION: Roof deck must be smooth, dry and free from warped surfaces. It is recommended that metal drip edges be installed at eaves and rakes.
PLYWOOD: All plywood shall be exterior grade as defined by the American Plywood Association. Plywood shall be a minimum of 3/8 in. thickness and applied in accordance with the recommendations of the American Plywood Association.
SHEATHING BOARDS: Boards shall be well-seasoned tongue-and-groove boards and not over 6 in. nominal width. Boards shall be a 1 in. nominal minimum thickness. Boards shall be properly spaced and nailed.
2. VENTILATION
Inadequate ventilation of attic spaces can cause accumulation of moisture in winter months and a build up of heat in the summer.
These conditions can lead to:
1. Vapor Condensation
2. Buckling of shingles due to deck movement.
3. Rotting of wood members.
4. Premature failure of roof.
To insure adequate ventilation and circulation of air, place louvers of sufficient size high in the gable ends and/or install continuous ridge and soffit vents. FHA minimum property standards require one square foot of net free ventilation area to each 150 square feet of space to be vented, or one square foot per 300 square feet if a vapor barrier is installed on the warm side of the ceiling or if at least one half of the ventilation is provided near the ridge. If the ventilation openings are screened, the total area should be doubled. IT IS PARTICULARLY IMPORTANT TO PROVIDE ADEQUATE VENTILATION.
3. FASTENERS
WIND CAUTION: Extreme wind velocities can damage these shingles after application when proper sealing of the shingles does not occur. This can especially be a problem if the shingles are applied in cooler months or in areas on the roof that do not receive direct sunlight. These conditions may impede the sealing of the adhesive strips on the shingles. The inability to seal down may be compounded by prolonged cold weather conditions and/or blowing dust. In these situations, hand sealing of the shingles is recommended. Shingles must also be fastened according to the fastening instructions described below. FASTENING PATTERNS: Fasteners must be placed 5-1/2 in. from the bottom edge of the shingle, penetrating through the common bond, and located horizontally as follows: 1) Standard Fastening Pattern. (For use on decks with slopes 2 in. per foot to 21 in. per foot.) One fastener 1 in. back from each end and one 12 in. back from each end of the shingle for a total of 4 fasteners. (See standard fastening pattern as listed with product manufacturer.
NAILS: Recommend the use of nails as the preferred method of application. Standard type roofing nails should be used. Nail shanks should be made of minimum 12 gauge wire, and a minimum head diameter of 3/8 in. Nails should be long enough to penetrate 3/4 in. into the roof deck. Where the deck is less than 3/4 in. thick, the nails should be long enough to penetrate completely through plywood decking and extend at least 1/8 in. through the roof deck. Drive nail head flush with the shingle surface.
STAPLES: If staples are used in the attaching process, follow the above instructions for placement. All staples must be driven with pneumatic staplers. The staple must meet the following minimum dimensional requirements. Staples must be made from a minimum 16 gauge galvanized wire. Crown width must be at least 15/16 in. (staple crown width is measured outside the legs). Leg length should be a minimum of 1-1/4 in. for new construction and 1-1/2 in. for reroofing thus allowing a minimum deck penetration of 3/4 in. The crown of the staple must be parallel to the length of the shingle. The staple crown should be driven flush with the shingle surface. Staples that are crooked, underdriven or overdriven are considered improperly applied.
CAUTION: ALL FASTENERS MUST BE DRIVEN INTO THE NAIL ZONE/COMMON BOND .
4. UNDERLAYMENT
UNDERLAYMENT: An underlayment consisting of asphalt saturated felt must be applied over the entire deck before the installation of shingles. Failure to add underlayment can cause premature failure of the shingles which is not covered by most manufacturer's limited warranty. Apply the felt when the deck is dry. On roof decks 4 in. per foot and greater apply the felt parallel to the eaves lapping each course of the felt over the lower course at least 2 in. Where ends join, lap the felt 4 in. If left exposed, the underlayment felt may be adversely affected by moisture and weathering. Laying of the underlayment and the shingle application must be done together. Products which are acceptable for use as underlayment are: – No. 15 Asphalt Saturated Organic Felt – A non-perforated asphalt saturated organic felt which meets ASTM: D226, Type I or ASTM D4869, Type I – Any non-perforated asphalt saturated organic felt In areas where ice builds up along the eaves or a back-up of water from frozen or clogged gutters is a potential problem, A waterproofing underlayment (or any specialty eaves flashing product) may be applied to eaves, rakes, ridges, valleys, around chimneys, skylights or dormers to help prevent water damage. Read manufacturer's installation literature for approved products.
5. APPLICATION INSTRUCTIONS:
STARTER COURSE: A starter course may consist of a manufacturers' starter , self-sealing 3-tab shingles or a 9 inch wide strip of mineral surface roll roofing. If self-sealing 3-tab shingles are used, remove the exposed tab portion and install with the factory applied adhesive adjacent to the eave. Attach the starter course with approved fasteners along a line parallel to and 3 in. to 4 in. above the eave edge. The starter course should overhang both the eave and rake edges 1/4 in. to 3/8 in. If a roll roofing is used, seal down the shingles in the first course by applying adhesive cement in four spots equally spaced to the surface of the starter strip and press the shingle down on the spots of cement. Plastic cement should be used sparingly, as excessive amounts may cause blistering.
SHINGLE APPLICATION: Start the first course with a full size shingle and overhang the rake edge 1/4 in. Cut 8 in. from a full shingle to form a shingle 29 in. long. Use this to start the second course (see diagram below). Cut a 23 in. long shingle to start the third course. Use the remaining 14 in. piece of shingle to start the fourth course and use the remaining 8 in. piece to begin the fifth course. Continue up the rake in as many rows as necessary using the same formula as outlined above. The butt of the shingle should be aligned with the top edge of the sawtooth of the underlying shingle for a 5 in. exposure (see shingle application drawing illustrated on this panel). When you make your final cut at the roof’s edge, flip any pieces that are 8 in. or longer back onto the roof. These pieces can be worked in anywhere without creating zippers or color variations.
NOTE: Do not align joints of shingle courses when working in cut pieces. Joints should be no closer than 4 in. from one another. 6. LOW SLOPE APPLICATION On pitches 2 in. per foot to 4 in. per foot cover the deck with two layers of asphalt saturated felt. Begin by applying the felt in a 19 in. wide strip along the eaves and overhanging the drip edge by 1/4 to 3/4 in. Place a full 36 in. wide sheet over the 19 in. wide starter piece, completely overlapping it. All succeeding courses will be positioned to overlap the preceding course by 19 in. If winter temperatures average 25°F or less, thoroughly cement the felts to each other with plastic cement from eaves and rakes to a point of a least 24 in. inside the interior wall line of the building. As an alternative, self-adhering waterproofing underlayment may be used in lieu of the cemented felts. 7. MANSARD ROOF OR STEEP SLOPE ROOF If the slope exceeds 21 in. per foot (60°), each shingle must be sealed with quick setting asphalt adhesive cement immediately upon installation. Spots of cement must be equivalent in size to a $.25 piece and applied to shingles with a 5 in. exposure, use 6 fasteners per shingle. See Section 3 for the Mansard Fastening Pattern. 8. RE-ROOFING Before re-roofing, be certain to inspect the roof decks. All plywood shall meet the requirements listed in Section 1. Nail down or remove curled or broken shingles from the existing roof. Replace all missing shingles with new ones to provide a smooth base. Shingles that are buckled usually indicate warped decking or protruding nails. Hammer down all protruding nails or remove them and refasten in a new location. Remove all drip edge metal and replace with new. If re-roofing over an existing roof where new flashing is required to protect against ice dams (freeze/thaw cycle of water and/or the backup of water in frozen or clogged gutters), remove the old roofing to a point at least 24 in. beyond the interior wall line and apply waterproofing underlayment. The nesting procedure described below is the preferred method for re-roofing over square tab strip shingles with a 5 in. exposure. Starter Course: Begin by cutting shingles into 5 x 36 inch strips. This is done by removing the 5 in. tabs from the bottom and approximately 2 in. from the top of the shingles so that the remaining portion is the same width as the exposure of the old shingles. Apply the starter piece so that the self-sealing adhesive lies along the eaves and is even with the existing roof. The starter strip should be wide enough to overhang the eaves and carry water into the gutter. Remove 3 in. from the length of the first starter shingle to ensure that the joints from the old roof do not align with the new. First Course: Cut off approximately 2 in. from the bottom edge of the shingles so that the shingles fit beneath the existing third course and align with the edge of the starter strip. Start the first course with a full 36 in. long shingle and fasten according to the instructions printed in Section 3. Second and Succeeding Courses: According to the off-set application method you choose to use, remove the appropriate length from the rake end of the first shingle in each succeeding course. Place the top edge of the new shingle against the butt edge of the old shingles in the courses above. The full width shingle used on the second course will reduce the exposure of the first course to 3 in. The remaining courses will automatically have a 5 in. exposure. 9. VALLEY APPLICATION Over the shingle underlayment, center a 36 in. wide sheet of a minimum 50 lb. roll roofing in the valley. Nail the felt only where necessary to hold it in place and then only nail the outside edges. IMPORTANT: PRIOR TO INSTALLATION WARM SHINGLES TO PREVENT DAMAGE WHICH CAN OCCUR WHILE BENDING SHINGLES TO FORM VALLEY. After valley flashing is in place: • Apply the first course of shingles along the eaves of one of the intersecting roof planes and across the valley. Note: For proper flow of water over the trimmed shingle, always start applying the shingles on the roof plane that has the lower slope or less height. • Extend the end shingle at least 12 in. onto the adjoining roof. Apply succeeding courses in the same manner, extending them across the valley and onto the adjoining roof. • Press the shingles tightly into the valley. • Use normal shingle fastening methods. Note: No fastener should be within 6 in. of the valley centerline, and two fasteners should be placed at the end of each shingle crossing the valley. • To the adjoining roof plane, apply one row of shingles vertically facing the valley and 2 in. back from the valley centerline. Note: For a neater installation, snap a chalkline over the shingles for guidance. • To complete the valley, apply shingles on the adjoining roof plane by positioning the tip of the first shingle of each row at the 2 in point from the centerline where the edge of the vertical shingle has been applied, covering the vertical shingle. 10. HIP AND RIDGE FASTENING DETAIL Apply the shingles with a 5 in. exposure beginning at the bottom of the hip or from the end of the ridge opposite the direction of the prevailing winds. Secure each shingle with one fastener on each side, 5-1/2 in. back from the exposed end and 1 in. up from the edge.
