The basic process: measure, prepare, nail, and seal
Installing roof shingles means laying overlapping rows of shingles across your roof deck, nailing each one down, and sealing the edges so water runs off rather than under them. The work happens in stages: you start at the bottom edge of the roof and work upward, overlapping each row so that water flows down and off. Each shingle gets nailed at specific points, and the nails must sit at the right depth — too shallow and they'll back out, too deep and they'll tear the shingle.
The actual nailing takes the most time. A typical roof might need 300 to 500 nails, depending on size. You'll use a roofing nailer (pneumatic or cordless) or a hammer, and you'll spend most of your day on a ladder or roof staging, repeating the same motion. The job is physically demanding and exposes you to fall risk, which is why many homeowners hire a contractor instead of doing it themselves.
Key Takeaways
- Shingles install in overlapping rows from the bottom of the roof upward, with each row offset so water sheds downward.
- Each shingle gets nailed at four or five points, and nails must sit flush with the shingle surface without tearing it.
- Starter shingles (cut or reversed) go along the bottom edge first, and ridge caps finish the peak.
- The job requires working at height on a sloped surface, which creates significant fall risk even for experienced workers.
- Mistakes in nail placement, overlap, or sealing lead to leaks that may not show up for months or years.
What you need before you start
Gather your materials and tools before you get on the roof. You'll need bundles of shingles (count your roof area in squares — one square equals 100 square feet — and buy one bundle per square plus 10 percent extra for waste and mistakes). You'll also need roofing nails (typically 1.25 inches long for asphalt shingles), a roofing nailer or hammer, a utility knife, a tape measure, and a chalk line.
Safety equipment is not optional. Wear a harness and rope if your roof pitch is steep (anything over 6:12 pitch, meaning 6 inches of rise for every 12 inches of run). Use a roof ladder or staging to prevent sliding. Wear work gloves, long sleeves, and closed-toe boots with good grip. Asphalt shingles get hot in sun and become slippery; work early in the day or on a cool day if possible.
Check that your roof deck is sound. If you're replacing old shingles, you may be able to nail over them, but if the deck is soft, rotted, or uneven, you'll need to repair or replace it first. Water damage underneath means the shingles won't hold properly and the problem will get worse.
Preparing the roof and laying starter shingles
Start at the bottom edge of the roof, along the eave. Snap a chalk line parallel to the eave, about 11 inches up from the edge (this accounts for the overlap of the first full row). This line keeps your first row straight.
Lay starter shingles along the eave. These are either full shingles laid upside down (so the adhesive strip faces up) or cut shingles made specifically as starters. The starter row creates a solid base so water doesn't run under the first full row of shingles. Nail the starter row with four nails per shingle, spaced about 12 inches apart and positioned about 1 inch above the adhesive strip.
Once the starter row is down, snap another chalk line about 5 inches above it (the exposure of a standard shingle). This line guides your first full row. Lay the first row of shingles with the tabs pointing down, offsetting the first shingle so that its right edge aligns with the center of the first starter shingle. This offset prevents the seams from lining up vertically, which would create a weak point.
Nailing and overlapping each row
Each shingle gets four nails, positioned in a line about 1 inch above the adhesive strip (the dark band on the shingle). Space the nails roughly 12 inches apart, starting about 1 inch from the left edge. Drive each nail so the head sits flush with the shingle surface — not sinking into it, not sticking out. A pneumatic nailer set to the right pressure will do this consistently; a hammer requires more judgment and takes longer.
After nailing, press down on the adhesive strip to set up the seal. Most modern shingles have a self-adhesive strip that bonds the shingle to the one below it, creating a stronger hold and a better water seal. This bond takes a few hours to set fully, so avoid walking on freshly installed shingles if possible.
Lay the second row so that its seams fall halfway between the seams of the first row. This staggered pattern is called a "running bond" and distributes stress evenly. Continue this pattern upward, snapping a new chalk line every few rows to keep them straight. On a long roof, rows can drift without a guide.
Handling roof features and obstacles
Chimneys, vents, and valleys require cuts and careful sealing. For a vent pipe, cut a hole in the shingle to fit around the pipe, then nail the shingle down. Slide the vent flashing (a metal or rubber collar) over the pipe and under the shingle above it, so water flows over the flashing and down. Seal the edges with roofing cement.
Valleys (the low points where two roof planes meet) need special attention because they channel water. Some roofers use a valley flashing (a metal strip) under the shingles; others weave shingles from both sides into the valley. Either way, the goal is to create a continuous path for water to flow down without pooling or backing up under the shingles.
Roof edges (the sides where shingles meet the fascia) need to be trimmed so they don't overhang more than about 0.75 inches. Trim shingles with a utility knife, using a straightedge as a guide. Seal the cut edges with roofing cement to prevent water from entering the cut.
Finishing the ridge and peak
When you reach the peak, the shingles from both sides will meet at the ridge. Trim the shingles so they meet at the peak without overlapping too much. Then install ridge cap shingles, which are either cut from standard shingles or purchased as pre-made caps. Ridge caps fold over the peak and nail down on both sides, creating a seal at the highest point of the roof.
Each ridge cap gets four nails — two on each side, positioned so they'll be covered by the next cap shingle. The overlap on ridge caps is typically 5 to 6 inches, the same as the field shingles below. Seal the final cap with roofing cement to prevent wind from lifting it.
Common mistakes that lead to leaks
Nails driven too deep tear the shingle and create a hole for water. Nails driven too shallow back out over time, especially in heat or wind. Either way, the shingle loses its hold and water gets underneath. This is the most common installation error and the hardest to spot until a leak shows up inside the house.
Misaligned rows and poor overlap create seams that line up vertically, allowing water to run between shingles rather than over them. Skipping the chalk line to save time almost always results in rows that drift and seams that align.
Forgetting to seal flashing around vents and chimneys is another frequent cause of leaks. The shingles alone won't keep water out at these penetrations; the flashing and sealant do. If you skip this step, water will find its way under the flashing and into the attic.
When to hire a contractor instead
Roof work is high-risk. Falls from ladders and roofs cause serious injury and death. If your roof is steep, high, or complex (multiple valleys, many penetrations), a contractor is the safer choice. Contractors have fall protection equipment, insurance, and experience working at height. They also have roofing nailers and can work faster, which means less time exposed to weather and fall risk.
A contractor's labor cost varies by region and roof complexity, but expect to pay $3 to $10 per square foot for installation alone. That's significant, but it includes the risk management and the warranty that comes with professional work. If the job goes wrong, the contractor's insurance covers it, not your homeowner's policy.
Frequently Asked Questions
Can I install new shingles over old ones?
Yes, in most cases. Nailing over existing shingles is faster and cheaper than tearing off the old layer first. However, the deck must be solid and the old shingles must be relatively flat. If the old shingles are curled, missing, or the deck is soft, tear them off first. Building codes in some areas limit you to two layers total, so check your local rules before starting.
What's the difference between three-tab and architectural shingles?
Three-tab shingles are flat and uniform, with three tabs per shingle. Architectural (or laminate) shingles have a thicker, layered look and better wind resistance. Both install the same way, but architectural shingles cost more and last longer. The installation process is identical.
How long does a roof installation take?
A typical residential roof takes one to three days for a contractor, depending on size and complexity. A single person working alone might take a week or more. Weather delays the work — rain stops progress, and heat makes shingles soft and hard to handle.
Do I need to seal the nails with roofing cement?
No, not for the field shingles. Modern shingles have self-adhesive strips that seal around the nails. However, you do need to seal flashing, cut edges, and any exposed nail heads with roofing cement to prevent water entry.
What happens if I nail through the adhesive strip?
The nail will puncture the strip and create a hole for water. Nails should go through the shingle above the adhesive strip, about 1 inch up. This way, the adhesive strip seals around the shingle below without a nail hole in it.