Asphalt Shingle Installation Guide

A shingle roof is a complete water-management system.

Architectural shingles are the visible surface, but long-term performance depends on the roof deck, ice protection, underlayment, edge metal, starter, fastening, flashing, ventilation, and drainage working together.

This is an educational field guide to the concealed work that separates a durable shingle roof from a roof that only looks finished.

• Use the current installation instructions printed on the shingle wrapper and published by the selected manufacturer as the controlling product requirements.
• Confirm the exact shingle, starter, underlayment, ice-and-water membrane, hip-and-ridge product, fasteners, ventilation plan, slope, and warranty level before work begins.
• Do not mix fastening patterns, exposure dimensions, offsets, or accessories from unrelated shingle systems.
• Treat sealant as a specific detail or secondary defense. It does not replace correct layering, flashing, fastening, or drainage.

Asphalt shingles are a water-shedding roof covering, not a waterproof membrane. Roof slope determines whether shingles belong on the roof and how the underlayment must be installed.

• Never install shingles below the minimum slope allowed by the selected manufacturer and applicable code.
• IKO Cambridge instructions prohibit installation below 2:12 and require special low-slope underlayment from 2:12 to less than 4:12.
• Roof sections near the minimum slope require deliberate planning at valleys, walls, crickets, and transitions where water can slow down or back up.
• A roof with mixed slopes may require more than one roofing system. Do not force shingles onto a section that needs a membrane roof.

A replacement roof should begin with a controlled tear-off that exposes the deck and keeps the structure protected from weather.

• Remove existing roofing and loose underlayment so the deck, penetrations, walls, valleys, and prior repairs can be inspected.
• Protect landscaping, siding, windows, equipment, and finished surfaces before tear-off begins.
• Stage removal so exposed areas can be repaired and dried-in before weather reaches the structure.
• Remove abandoned fasteners, loose metal, deteriorated flashings, and debris that would interfere with a flat assembly.

The roof deck must be smooth, firm, clean, dry, securely fastened, and compatible with the selected shingle system.

• Verify sheathing type, thickness, fastening, span, plane, and moisture condition against code and manufacturer requirements.
• Replace deteriorated or delaminated sheathing and correct unsupported edges, raised fasteners, gaps, and abrupt surface changes.
• Do not use shingles to hide a soft, uneven, wet, or structurally questionable deck.
• Confirm that repairs around skylights, chimneys, walls, and penetrations leave enough sound substrate for secure flashing and fastening.

Ventilation is part of the roof assembly. Intake and exhaust must be balanced and connected through a clear air path.

• Inspect soffit intake, baffles, attic obstructions, exhaust vents, and any separate attic zones before choosing the ventilation layout.
• Do not add exhaust ventilation without confirming that the assembly has adequate intake air.
• Keep insulation and stored materials from blocking the ventilation path at the eaves.
• Size and locate ventilation according to the building design, product requirements, and applicable code.

Self-adhered membrane provides backup protection at the roof areas most exposed to ice, concentrated water, and wind-driven weather.

• Install eave protection to the distance required by code and the selected manufacturer, measured beyond the interior face of the exterior wall where applicable.
• Protect valleys, penetrations, roof-to-wall joints, chimneys, crickets, and other vulnerable transitions as required by the approved assembly.
• Apply membrane to a clean, dry, compatible substrate and roll or press it into full contact without trapped voids or fishmouths.
• Lap and terminate membrane so water cannot run behind edge metal or flashing.

Underlayment is the secondary water-control layer beneath the shingles and must cover the deck continuously with drainage-positive laps.

• Install the approved synthetic or felt underlayment in courses that shed water, with side laps, end laps, and fastening that match the product instructions.
• Keep the underlayment tight and flat. Repair tears, wrinkles, open laps, and damaged areas before shingles are installed.
• At low slopes, use the special underlayment assembly required by the shingle manufacturer. IKO Cambridge allows double-coverage underlayment or a full layer of approved ice-and-water protector from 2:12 to less than 4:12.
• Coordinate underlayment with valleys, walls, penetrations, and edge metal so no reverse laps are buried beneath the finished roof.

Eave and rake edge metal protects the deck edge, directs water away from the fascia, and anchors the perimeter of the roof assembly.

• Sequence eave and rake metal with the underlayment according to the selected assembly so every layer drains outward.
• Fasten edge metal with corrosion-resistant fasteners at the spacing required by code and manufacturer instructions.
• Lap adjoining pieces in the drainage direction and secure corners without leaving open joints or sharp, unsupported edges.
• Coordinate drip edge projection, starter overhang, gutter position, fascia condition, and intake ventilation before shingles begin.

A purpose-made starter course seals the first field course and strengthens the roof perimeter against wind uplift.

• Use an approved starter product at both eaves and rakes when required by the shingle system and warranty.
• Position the factory sealant where it can bond to the overlying field shingle.
• Maintain the manufacturer-approved overhang at eaves and rakes; IKO Cambridge specifies 1/4 inch to 3/4 inch for its starter and field courses.
• Offset starter joints from the joints in the first shingle course and fasten the starter exactly as directed.

Straight courses and deliberate offsets protect the water path, keep joints separated, and create a balanced finished appearance.

• Use chalk lines to control alignment instead of allowing small course errors to build across the roof plane.
• Follow the exposure printed for the exact product. IKO Cambridge uses a 5-7/8 inch exposure.
• Maintain the manufacturer-approved offset sequence and minimum separation between joints in adjacent courses.
• Plan the layout at rakes, valleys, penetrations, dormers, and walls so narrow pieces and stacked joints are avoided.

Correct nail location, penetration, angle, and seating are essential to wind resistance and warranty compliance.

• Place every fastener in the manufacturer’s designated nail zone. High nailing can miss the common bond and leave the shingle inadequately attached.
• Drive nails straight and flush with the shingle surface—never crooked, underdriven, or cutting through the mat.
• Use corrosion-resistant roofing nails with the required head diameter, shank length, and deck penetration for the assembly.
• Use the product-specific nail count. IKO Cambridge calls for four nails in standard application and six nails for its steep-slope or high-wind application.

Factory seal strips need adequate heat and clean contact to activate. Cold, dust, shade, and wind can delay or prevent sealing.

• Keep shingles flat and handle them carefully in cold weather to avoid cracking or damage.
• Confirm whether the manufacturer requires manual sealing because of temperature, wind, dust, steep slope, season, or exposure.
• Apply only the approved amount and type of roofing cement in the specified locations. Excess material can damage or blister shingles.
• Store hip-and-ridge materials as directed so they can bend without cracking during cold-weather installation.

A valley carries water, snowmelt, ice, and debris from two roof planes. It requires a protected substrate, durable liner, clear waterway, and disciplined fastening.

• Install the valley membrane and metal liner before field shingles enter the valley.
• Size the membrane, metal, open waterway, and widening pattern according to the manufacturer, valley length, slope, and expected drainage.
• Keep fasteners out of the high-flow center and observe the required setback from cut edges.
• Clip upper corners and seal cut shingle ends only where and how the selected detail requires so water is directed into the valley.

A correct roof-to-wall joint uses base flashing and counterflashing integrated with the wall drainage plane.

• Use individual step flashing at sidewalls where required, woven with the shingle courses and sized for the actual roof and wall condition.
• Install headwall and chimney flashing so water from the wall drains onto the roof surface, not behind the roofing.
• Integrate counterflashing behind siding, stucco drainage components, or a masonry reglet as appropriate.
• Provide kickout flashing at lower wall terminations and crickets or diverters where roof geometry concentrates water.

Every penetration interrupts the shingle courses and underlayment, so its flashing must be integrated into both water-control layers.

• Replace deteriorated pipe flashings, vents, and accessories rather than burying old components beneath a new roof.
• Set the lower flange over the shingles below and weave the side and upper flange beneath the courses above.
• Keep nails out of exposed water paths and place sealant only where the approved detail requires it.
• Use a cricket, curb, or fabricated diverter for large penetrations and locations that collect water or snow.

Hip-and-ridge shingles finish the high points of the roof while protecting the field-shingle terminations and ventilation openings.

• Use the approved hip-and-ridge product for the selected shingle system, warranty, impact rating, and desired finished profile.
• Maintain the required exposure, fastener position, penetration, and prevailing-wind installation direction.
• Keep ridge-vent slots within the vent manufacturer’s dimensions and preserve solid nailing at the ends and transitions.
• Seal exposed final fasteners with compatible roofing cement as directed by the manufacturer.

A finished shingle roof is not complete until the hidden layers, visible work, attic conditions, and drainage path have been reviewed together.

• Verify course alignment, exposure, offsets, nail placement, starter, seal-strip contact, and high-wind or manual-sealing requirements.
• Inspect every eave, rake, valley, hip, ridge, wall, chimney, cricket, penetration, transition, and flashing lap.
• Confirm edge metal, gutters, downspouts, intake, exhaust, and roof-to-wall interfaces operate as one assembly.
• Remove debris and loose fasteners, clean gutters, and check siding, fascia, landscaping, and finished surfaces for damage.
• Photograph concealed details and retain product labels, installation records, ventilation calculations, and warranty information.

The shingle brand is only part of the answer.

Two contractors can quote the same shingle and color while proposing completely different roofing systems. Ask questions that reveal the work beneath the surface.

• 01Will the existing roof be removed so the deck and old flashing can be inspected?
• 02Which exact shingle system, starter, underlayment, ice protection, and hip-and-ridge products are included?
• 03What slope limits and low-slope requirements apply to each roof section?
• 04Where will ice-and-water membrane be installed for this Northern Arizona home?
• 05How will valleys, sidewalls, headwalls, chimneys, skylights, and pipe penetrations be flashed?
• 06What nail pattern, nail zone, and high-wind requirements apply to the selected shingle?
• 07How will intake and exhaust ventilation be calculated and verified?
• 08How will cold-weather sealing be handled if the shingles cannot activate naturally?
• 09Will I receive photographs of the deck, membrane, flashing, and other concealed work before it is covered?