Shingle installation follows a bottom-to-top pattern, starting at the roof edge and working toward the peak

Roof shingles are installed in overlapping rows that shed water downward, beginning at the lowest edge of the roof and moving upward. Each shingle is nailed in place and overlapped by the row above it, so water runs over the seams rather than into them. The process requires measuring, cutting, nailing, and sealing — and the roof must be prepared before the first shingle goes down.

Most residential roofs use asphalt shingles, which come in bundles of three. A typical bundle covers about 33 square feet. Installation takes one to three days depending on roof size and pitch, and the work is physically demanding — you spend hours on a slope, carrying materials, and working with a hammer or nail gun in all weather.

Key Takeaways

  • The roof deck must be clean, dry, and covered with underlayment and drip edge before shingles are installed.
  • Shingles are nailed in a specific pattern starting at the bottom edge, with each row overlapping the one below it.
  • Nails must be driven into the nail line marked on each shingle, usually four nails per shingle, and must sit flush with the surface.
  • Starter shingles or cut shingles are used at the bottom edge to create a proper overlap pattern.
  • Roof pitch, weather conditions, and your comfort working at heights all affect whether this is a job to hire out or attempt yourself.

Preparing the roof deck and underlayment

Before any shingle is nailed down, the roof deck — the plywood or OSB layer underneath — must be inspected and repaired. Any soft, rotted, or missing sections should be replaced. The deck is then covered with underlayment, a water-resistant barrier that catches leaks if water gets under the shingles. Underlayment comes in rolls and is stapled or nailed to the deck, overlapping each row by at least 2 inches.

Once underlayment is down, drip edge — a metal strip that directs water away from the fascia — is nailed along the bottom edge of the roof and along the gable ends. The drip edge at the bottom sits on top of the underlayment; the drip edge at the gables sits under it. This overlap pattern prevents water from running behind the drip edge and into the fascia.

Installing starter shingles at the roof edge

The first row of shingles is called the starter course. Rather than using full shingles, many roofers cut shingles in half or use shingles installed upside down, so the adhesive strip and tabs face upward. This creates a solid base for the first full row to overlap. Starter shingles are nailed along the bottom edge of the roof, with nails driven into the nail line — the area marked on the shingle where nails should go.

Spacing matters: starter shingles should be nailed every 8 to 10 inches along the edge. Each nail should be driven straight in and sit flush with the shingle surface — not protruding, not sunk below the surface. A protruding nail can catch water; a sunken nail can tear the shingle.

Laying the first full row of shingles

The first full row of shingles is laid directly over the starter course, with the tabs facing downward. The first shingle in the row is positioned so it overhangs the gable edge by about half an inch, then nailed with four nails driven into the nail line. The next shingle is placed beside it, overlapping by about half an inch, and nailed the same way.

The row continues across the roof until you reach the opposite gable. The last shingle will likely need to be cut to fit. Measure the remaining space, mark the shingle on the back, and cut it with a utility knife. Nail it in place and seal the cut edge with roofing cement to prevent water from entering the cut.

Creating the offset pattern for subsequent rows

Each row of shingles is offset from the row below it so the seams do not line up vertically — this prevents water from running straight down through the seams. The offset is usually 6 inches, meaning the second row starts with a shingle cut 6 inches shorter than a full shingle. The third row starts with a shingle cut 12 inches shorter, and so on, until the pattern repeats.

This offset pattern is called staggering. It requires cutting shingles to different lengths and keeping track of where each row starts. Some roofers mark the roof with chalk lines to keep rows straight and evenly spaced. Rows should be spaced so the bottom edge of each shingle sits about 5 inches below the top of the tabs on the row below it.

Nailing and sealing each shingle

Every shingle is nailed with four nails driven into the nail line — the area marked on the shingle, usually just above the tabs. Nails should be 1 to 1.25 inches long for asphalt shingles over underlayment. Each nail should be driven straight in, perpendicular to the roof surface, and sit flush with the shingle. A nail gun set to the correct pressure makes this faster and more consistent than hand-nailing, but either method works if done carefully.

In windy climates or on steep roofs, some roofers explore a small dab of roofing cement under each tab to seal it to the shingle below. This is not always required but adds wind resistance. Cement is applied with a caulk gun in a small bead under the tab, then the shingle is pressed down to set it.

Working around roof features and reaching the peak

Chimneys, vents, and skylights interrupt the shingle pattern and require cutting and fitting shingles around them. For a vent pipe, shingles are cut to fit around the pipe, and a rubber flashing collar is slipped over the pipe and nailed to the roof. Shingles are then laid over the top of the flashing so water runs over it. Chimneys and skylights use similar logic: flashing is installed first, then shingles are fitted around it.

As you approach the peak, rows become shorter because the roof narrows. The final row at the peak is cut to fit the remaining space, and the seam where the two sides of the roof meet is sealed with roofing cement. Ridge shingles — shingles cut into three tabs and folded over the peak — are then nailed along the ridge, overlapping each other, to cap the roof and shed water on both sides.

Frequently Asked Questions

How many nails does each shingle need?

Standard asphalt shingles require four nails per shingle, driven into the nail line marked on the shingle. Some high-wind areas require six nails. Nails should be 1 to 1.25 inches long and driven perpendicular to the roof surface, sitting flush with the shingle.

What happens if I nail in the wrong spot?

Nails driven outside the nail line can tear the shingle or miss the deck entirely, leaving the shingle loose. Nails driven too high can puncture the shingle above it. If you miss the mark, pull the nail out and drive a new one in the correct spot. Do not leave the old nail hole; it will leak.

Can I install shingles in cold or wet weather?

Asphalt shingles have an adhesive strip that activates in warm weather. In temperatures below 50°F, the adhesive does not seal properly, and shingles may blow off or curl. Wet conditions make the roof slippery and dangerous. Most roofers wait for dry weather above 50°F.

Do I need to remove old shingles before installing new ones?

Building codes in most places allow one layer of new shingles to be installed over one layer of old shingles. A second re-roof usually requires removing the old shingles first. Check your local building code before deciding; some jurisdictions require removal regardless of how many layers exist.

What is the difference between three-tab and architectural shingles?

Three-tab shingles are flat and uniform, with three tabs per shingle. Architectural shingles have a thicker, textured appearance with varying tab sizes and depths. Both are installed the same way. Architectural shingles last longer and look more like wood or slate, but cost more.