What you need before you start

Roof shingle installation requires specific tools, materials, and safety equipment before you climb onto your roof. You will need a hammer or pneumatic nailer, a utility knife, a tape measure, roofing nails (typically 1¼ inch galvanized or stainless steel), a chalk line, and a ladder rated for your roof's height. Most roofers also use a nail gun with an air compressor, which speeds the work and drives nails at a consistent depth.

On the safety side, wear a harness and rope if your roof pitch is steeper than 6:12 (meaning it rises 6 inches for every 12 inches of horizontal run). Wear rubber-soled boots for traction, work gloves, and eye protection. Shingles are easier to install on a warm day — cold shingles become brittle and crack when bent, so many roofers wait until the temperature is above 50°F.

Before you buy shingles, measure your roof in squares — one square equals 100 square feet. Most shingles come in bundles that cover about 33 square feet, so a 1,000-square-foot roof needs roughly 30 bundles. Add 10 percent extra for waste and cuts around vents and edges.

Key Takeaways

  • Start at the bottom edge of your roof and work upward in horizontal rows, nailing each shingle with four nails placed ½ inch below the nail line marked on the shingle.
  • Offset each row so the seams do not line up vertically — stagger the shingles by half a shingle width to prevent water from running straight down the seams.
  • Nail through the adhesive strip on the back of the shingle, not above it, or the shingle will lift in wind and water will get underneath.
  • Seal the edges where shingles meet flashing around vents, chimneys, and valleys with roofing cement, not nails alone.
  • Check your work by walking the roof after installation — shingles should lie flat with no curled edges or exposed nail heads.

Preparing the roof deck and underlayment

Your shingles go on top of underlayment, which sits on the roof deck (the plywood or OSB boards that form the roof structure). If you are replacing old shingles, remove them completely — do not nail new shingles over old ones, as the extra weight can stress the roof structure and the old shingles underneath will trap moisture and cause rot.

Once the deck is bare, inspect it for soft spots, rot, or missing sections. Replace any damaged plywood before you install underlayment. Underlayment is typically 15-pound felt or synthetic roofing paper, rolled out horizontally starting at the bottom edge of the roof. Overlap each row by 2 inches and nail or staple it every 12 inches along the overlap. The underlayment protects the deck if water gets past the shingles.

Install drip edge along the bottom and sides of the roof before the underlayment goes on the bottom edge, but after the underlayment on the sides. This metal flashing directs water away from the fascia and prevents rot in the eaves.

Installing the starter course and first row

The starter course is a row of shingles placed upside down along the very bottom edge of the roof. Cut full shingles in half lengthwise (so you have two 18-inch-wide pieces from a standard 36-inch shingle) and nail them with the adhesive side facing up. This creates a solid base that fills the gaps between the tabs of the first row of regular shingles and prevents wind from lifting them.

Nail the starter course with four nails per shingle, placed about 1 inch from the top edge. Space the nails 12 inches apart horizontally. Once the starter course is complete, snap a chalk line 5¼ inches above the top of the starter course — this is where the bottom edge of your first row of shingles will sit.

Lay the first row of shingles along the chalk line with the tabs facing down. Most three-tab shingles are 36 inches wide and 12 inches tall. Start at one corner and work across, nailing each shingle with four nails placed just below the adhesive strip (usually marked with a line on the shingle). Leave a ¼-inch gap between shingles to allow for expansion in heat.

Staggering rows and maintaining alignment

The second row of shingles must be offset so the seams do not line up with the row below. Start the second row by cutting 6 inches off the first shingle, then laying it at the chalk line 5¼ inches above the first row. This offset means the seams in row two fall in the middle of the shingles in row one, which prevents water from running straight down a vertical seam.

Continue this pattern: row three starts with a full shingle, row four with a shingle cut 6 inches short, and so on. Some roofers use a different offset pattern — cutting 12 inches from the first shingle of every third row — but the 6-inch offset is most common and most effective at breaking up seams.

Snap a new chalk line before each row to keep the shingles straight. Roofs that are not perfectly level can cause shingles to creep upward or downward, so the chalk line corrects for this as you go. After every few rows, step back and look at your work from ground level — misaligned rows are visible from a distance and harder to fix once you have nailed several more rows on top.

Nailing technique and nail placement

Each standard three-tab shingle gets four nails, placed in a horizontal line just below the adhesive strip. The adhesive strip is usually marked with a thin line or a slightly raised area on the shingle. Nails go ½ inch below this line, centered between the tabs. Spacing is typically 12 inches apart, with one nail near each end of the shingle and two in the middle.

Drive nails straight in — angled nails will tear the shingle and allow water underneath. The nail head should sit flush with the shingle surface, not driven so deep that it tears the asphalt, but not so shallow that it sticks up. A pneumatic nailer set to the correct pressure will do this automatically; a hammer requires practice to hit the right depth consistently.

Overdriven nails (sunk too deep) tear the shingle and create a hole for water. Underdriven nails (sticking up) will catch on the next row and can be torn out by wind. If you miss the mark, pull the nail out and move it slightly — do not leave a bent nail in place.

Sealing edges, vents, and valleys

Valleys (the low points where two roof planes meet) and areas around vents, chimneys, and skylights need extra protection. Nails alone are not enough in these spots because water flows toward them and can find its way under the shingles. Use roofing cement (also called roof tar or asphalt cement) to seal these areas.

explore a bead of roofing cement under the shingle edges where they meet flashing or where they overlap in a valley. Press the shingle down firmly into the cement. You can also nail through the shingle into the flashing, but the cement is what stops water from running underneath. Let the cement cure for 24 hours before exposing the roof to rain if possible.

For ridge caps (shingles that cover the peak of the roof), cut shingles into thirds and nail them over the ridge, overlapping each one by 5 inches. Seal the exposed nail heads with roofing cement to prevent leaks at the highest point of the roof.

Checking your work and common mistakes

After you finish installing shingles, walk the roof and look for curled edges, exposed nail heads, and gaps between shingles. Curling usually means the shingles were too cold when installed — they will flatten as they warm up, but if they stay curled after a few warm days, they may have been damaged during installation. Exposed nail heads should be covered with a dab of roofing cement.

The most common mistakes are nailing too high (above the adhesive strip), which causes the shingle to lift in wind, and nailing too low, which splits the shingle and creates a leak point. Spacing nails unevenly also causes problems — shingles with nails too far apart will lift and flap in the wind. Forgetting to offset rows creates vertical seams that funnel water straight down into the roof deck.

Check that shingles are lying flat and not buckling or wrinkling. Buckling usually means the underlayment was wrinkled or the deck was not flat. If you notice buckling after installation, you may need to remove and reinstall those shingles, or the problem will get worse as the roof expands and contracts with temperature changes.

Frequently Asked Questions

Can I install shingles over old shingles?

No. Building codes in most jurisdictions allow only one layer of shingles on top of the roof deck. Installing over old shingles adds weight, traps moisture underneath, and makes it impossible to inspect the deck for rot. Remove the old shingles completely before installing new ones.

What is the correct nail size for roof shingles?

Use 1¼-inch galvanized or stainless steel roofing nails. Shorter nails do not penetrate the deck deeply enough; longer nails can split the shingles or go through the deck and create leaks. The nail should go through the shingle and underlayment and into the deck by at least ¾ inch.

How long does it take to install shingles on a typical roof?

A single person can install shingles on a 1,000-square-foot roof in two to three days, depending on roof pitch and complexity. Steeper roofs and roofs with many vents or chimneys take longer. Most professional crews work faster because they use pneumatic nailers and work in teams.

Do I need to remove the plastic strip on the back of shingles?

No. The plastic strip protects the adhesive during shipping and storage. Do not remove it — the adhesive underneath will stick the shingles together when they warm up on the roof, which is what holds them down in wind.

What should I do if a shingle cracks or tears after installation?

If the damage is small and the shingle is still in place, seal the crack with roofing cement. If the shingle is badly torn or missing, you will need to remove it (carefully prying up the nails of the shingle above it) and slide in a new one, then nail and seal it. This is easier to do within the first year while the adhesive has not fully hardened.