The first few rows of a roof decide whether the whole thing sheds water or leaks. Knowing how to start shingles on a roof correctly means getting the starter strip, the first course, and the nailing pattern exactly right before you ever get into a rhythm, because every course above locks to the alignment and sealing you establish at the eave. Skip the starter strip, misplace a nail, or drift out of square, and you invite blow-offs and water intrusion at the most vulnerable edge of the roof. This guide walks through the setup and the critical first courses the way an experienced roofer approaches them.
Note that roofing is fall-hazard work. If your roof is steep, high, or complex, hiring a licensed contractor is the safer call. For a low-slope garage, shed, or accessory structure, a careful DIYer can handle it with the right prep.
Prep the Deck and Underlayment First
You cannot start shingles until the roof deck is sound and dry. Walk the deck and replace any soft, rotted, or delaminating plywood. Sweep it clean of debris and nails, then confirm the surface is dry; shingling over damp decking traps moisture and shortens the roof’s life.
Next comes the water barrier. In cold climates, install a self-adhering ice-and-water membrane along the eaves, extending at least 24 inches inside the interior wall line to guard against ice dams. Over the rest of the deck, roll out synthetic underlayment (or 15/30-lb felt), overlapping each course by the manufacturer’s specified amount, typically 2 to 4 inches, and running it up and over the ridge. This layer is your backup water plane.
Install Drip Edge and Flashing
Drip edge is metal flashing that directs runoff into the gutter and protects the deck edge. The sequence matters. Along the eaves, drip edge goes under the underlayment so water sheds over the metal into the gutter. Along the rakes (the gable ends), drip edge goes over the underlayment. Nail it every 12 inches or so, and overlap sections by a couple of inches in the direction of water flow.
Handle valleys, vent pipes, and wall flashings before shingling into them. Getting flashing right now saves you from cutting shingles back out later.
Lay the Starter Strip
This is the single most important step, and the one beginners most often skip. The starter strip is a course of shingles with the adhesive strip positioned at the eave edge, so the tabs of the first visible course seal down and resist wind uplift. It also fills the gaps between the cutouts of the first course, closing off a path water would otherwise find.
You can buy dedicated starter shingles or make your own by cutting the tabs off standard three-tab shingles. Install the starter strip so it overhangs the drip edge by about a quarter to three-eighths of an inch, and align the adhesive bead near the eave. Nail it 3 to 4 inches up from the edge, spacing nails roughly every 12 inches. Make sure no nail lands where a cutout in the first course will expose it.
- Overhang: 1/4 to 3/8 inch past the drip edge
- Adhesive: Positioned toward the eave to catch the first-course tabs
- Nails: High enough to be covered, about every 12 inches
Snap Chalk Lines for Alignment
Straight courses are not luck; they come from chalk lines. Measure up from the eave and snap a horizontal control line for the top of your first course, using the shingle’s exposure (usually about 5 to 5-5/8 inches for architectural shingles) to set the spacing. Snapping vertical lines every few feet as well helps you control the horizontal offset and keeps the pattern from wandering as you climb. Roofs are rarely perfectly square, so trust your chalk lines over the deck edge.
Set the First Course
Lay the first full course directly over the starter strip, aligned flush with the starter’s eave edge so both overhang the drip edge equally. This first course is the foundation for everything above, so take your time keeping it dead straight along your chalk line.
Nailing is critical. Use four nails per architectural shingle (six in high-wind zones), placed in the manufacturer’s designated nail zone, typically just below the sealant line. Drive nails flush, not tilted and not overdriven; an overdriven nail cuts into the mat, and a proud nail telegraphs through the shingle above. Never nail into the adhesive strip or above the nail line, which would leave the shingle unfastened at its lower edge.
Establish the Offset Pattern
Shingle courses must be staggered so the cutouts and seams never line up, which is what forces water to travel sideways before it can reach a seam. Start the second course by cutting a set amount off the first shingle, following the manufacturer’s stagger specification (commonly a 6-inch offset for three-tab or a random/roughly 6-inch offset for architectural). Continue the pattern up the roof, checking your horizontal chalk lines every few courses to stay true.
Maintaining a consistent offset does two things: it seals out water and it produces the clean, uniform appearance of a professional job.
Common Mistakes to Avoid
A few errors account for most first-timer roof failures. Learn them before you climb up.
- Skipping the starter strip: The first course lifts in wind and water seeps through the cutouts.
- Wrong nail placement: Nails too high leave shingles unsealed; too low, they show.
- Overdriven nails: They tear the mat and void warranties.
- Ignoring chalk lines: Courses drift and the pattern looks amateur.
- Wrong drip-edge order: Water gets behind the fascia instead of into the gutter.
Tools and Materials You’ll Need
Having the right gear staged before you climb up keeps the job moving and, more importantly, keeps you safe. Gather everything at ground level and haul it up in stages rather than making risky trips with your hands full.
- Roofing nailer or hammer: A pneumatic coil nailer speeds the work dramatically; a roofing hatchet works for small jobs.
- Roofing nails: Galvanized, long enough to penetrate the deck by at least three-quarters of an inch.
- Utility knife with hook blades: For clean shingle cuts.
- Chalk line and tape measure: For alignment.
- Roofing cement: For hand-sealing and flashing details.
- Safety gear: A roof harness, rope, soft-soled shoes, and a stable ladder are non-negotiable.
Order about 10 percent more shingles than your square-foot calculation to cover waste, cuts, and mistakes. Running short mid-project and having to match a dye lot later is a common and avoidable headache.
Estimating How Many Shingles You Need
Roofing is sold by the “square,” which equals 100 square feet of coverage. Measure the length and width of each roof plane, multiply for the area, and add them together, then divide by 100 to get your squares. Add roughly 10 percent for waste and starter courses, and more for a complex roof with many valleys and hips where cutting increases scrap. A standard bundle of architectural shingles covers about one-third of a square, so plan on three bundles per square. Knowing your total before you start means you buy from a single production run, which keeps the color consistent across the whole roof, a detail that matters more than beginners realize.
Weather and Timing
Shingles seal best in warm temperatures when the adhesive strips activate in the sun. In cold weather, tabs may not bond for weeks, so in high-wind or cold conditions, hand-seal the first courses with a dab of roofing cement under each tab. Never shingle a wet or frosty roof; both are unsafe and lead to poor adhesion.
Final Thoughts
Getting the start right is nine-tenths of a good roof. Prep and dry the deck, install underlayment and drip edge in the correct order, lay a proper starter strip, snap your chalk lines, and nail the first course precisely with the right offset. Do those steps carefully and the rest of the roof falls into an easy, repeatable rhythm. If any part of the job exceeds your comfort with heights or slope, bring in a professional; a roof is one project where a single leak can undo all the work above it.
