What you need before you start
Roof shingle installation requires specific tools, materials, and safety equipment before you climb onto the roof. You will need a hammer or pneumatic nailer, a utility knife, a tape measure, a chalk line, roofing nails (typically 1¼ inch), and the shingles themselves. Most roofers also use a roofing shovel or pry bar to remove old shingles if you are replacing rather than installing over existing material.
Safety equipment is non-negotiable. Wear a harness attached to a rope anchored above the roofline, use a ladder stabilizer, and wear rubber-soled boots with good grip. Work on a dry day — wet shingles are slippery and dangerous. If your roof pitch is steeper than 8:12 (meaning it rises 8 inches for every 12 inches of horizontal distance), consider hiring a professional; steep roofs require specialized equipment and experience.
Check your local building codes before starting. Some jurisdictions require permits for roof work, and inspectors may need to sign off on the installation. Your roofing material supplier can tell you what your area requires and whether you need to notify anyone before beginning.
Key Takeaways
- Shingles are installed from the bottom of the roof upward in overlapping rows, with each row offset so water runs down and off rather than into seams.
- Each shingle is fastened with four nails placed in a specific pattern — too few nails and wind will tear them loose; too many creates holes that leak.
- The first row (called the starter course) is installed upside down along the eave, then covered by the first full row of shingles right-side up.
- Roof penetrations like vents and chimneys require flashing (metal trim) installed before shingles go around them, not after.
- Installation takes one to three days depending on roof size and pitch; most homeowners hire professionals because the work is physically demanding and the cost of mistakes is high.
Preparing the roof deck and underlayment
Before any shingle goes down, the roof deck (the plywood or OSB underneath) must be solid and dry. If you are replacing shingles, remove the old ones completely using a roofing shovel or pry bar. Work from the peak downward, pulling nails as you go. Inspect the deck for soft spots, rot, or damage — any section that feels spongy needs to be cut out and replaced with new plywood of the same thickness.
Once the deck is clean and solid, install underlayment — a waterproof barrier that sits between the deck and the shingles. Most modern roofs use synthetic underlayment (which lasts longer than felt) or asphalt-saturated felt. Roll it out horizontally starting at the eave, overlapping each row by 4 to 6 inches so water runs down over the layer below. Fasten it with roofing nails or staples spaced about 12 inches apart. At the eave, the underlayment should hang over the edge slightly so water drips clear of the fascia board.
Install drip edge — a metal trim that runs along the eave and gable edges — before the underlayment at the eave and after the underlayment at the gables. This directs water away from the fascia and prevents rot. Nail it every 12 inches with roofing nails.
Installing the starter course and first row
The starter course is a row of shingles installed upside down along the eave, with the adhesive strip (or tar line) facing up. Cut the shingles in half lengthwise so you are working with 18-inch-wide pieces rather than full 36-inch shingles. Align the first piece so its edge is flush with the drip edge, then nail it down with four nails placed 5¾ inches from the bottom and spaced about 12 inches apart horizontally. Continue across the eave, butting each piece against the last one with no gap.
Once the starter course is complete, install the first full row of shingles right-side up, with the adhesive strip facing down. This row covers the starter course. Align the first shingle so it overhangs the starter course by about ½ inch, then nail it with four nails placed in the nail line (the line printed on the shingle, usually about 5¾ inches from the bottom). Space the nails roughly 12 inches apart. Continue across the roof, butting shingles tightly together.
The second row is offset by half a shingle width so the seams do not line up vertically — this overlap is what keeps water from running into the seams. Start the second row by cutting 6 inches off the first shingle, then laying it. The third row starts with a full shingle, the fourth row with 6 inches cut off, and so on. This pattern ensures proper water drainage and structural strength.
Nailing pattern and fastening
Each three-tab shingle (the most common type) gets four nails, placed in a horizontal line about 5¾ inches from the bottom edge. The nails should be spaced roughly 12 inches apart across the width of the shingle. Architectural or laminated shingles may have a different nail line printed on them — follow the manufacturer's marking, not a guess.
Drive nails straight in, not at an angle. The nail head should sit flush with the shingle surface, not driven so hard that it crushes the shingle or leaves a dent. If you use a pneumatic nailer, set the pressure so the nail seats properly without over-driving. Hand-nailing takes longer but gives you more control; use a hammer with a smooth face and strike the nail squarely.
Nailing too few times leaves shingles loose and vulnerable to wind damage. Nailing too many times creates extra holes that can leak. Stick to four nails per three-tab shingle. If you are installing architectural shingles, check the package instructions — some require five or six nails because of their weight and shape.
Working around roof penetrations and edges
Vents, chimneys, and other roof penetrations require flashing — metal trim that channels water away from the opening. Flashing must be installed before shingles are laid around it, not after. Slide the flashing under the shingles above the penetration and over the shingles below it, creating a water-shedding overlap. Nail the flashing to the roof deck, then seal the nails with roofing cement to prevent leaks.
At the gable edges (the sloped sides of the roof), shingles should overhang the edge by about ½ inch. Trim excess shingle material with a utility knife using a straightedge as a guide. At the ridge (the peak where two roof planes meet), shingles from both sides meet. You can either fold shingles over the ridge or install ridge cap shingles — pre-cut pieces designed specifically for this purpose. Ridge caps are nailed with two nails per piece, placed so they will be covered by the next cap shingle.
At the eave, shingles should overhang the drip edge by about ½ inch. This overhang directs water into the gutter rather than behind it. If your roof has no gutter, the overhang should be slightly less so water does not splash back onto the fascia.
Common mistakes and how to avoid them
The most common error is not removing old shingles before installing new ones. Layering shingles creates a thick, uneven surface that causes water to pool and shortens the life of the new shingles. Remove old material completely, even if it takes longer.
Another frequent problem is misaligning rows so seams line up vertically. This creates a path for water to run straight down into the layer below. Use the offset pattern described above — cut 6 inches off alternating rows — and check your work as you go. If a row is off by more than an inch or two, stop and adjust before moving forward.
Insufficient nailing is also common, especially when hand-nailing. Shingles that are under-nailed blow off in wind, exposing the layer below. Use four nails per shingle, placed in the nail line, and drive them flush. If you are unsure whether a nail is seated properly, tap it once more.
Finally, do not skip the underlayment or flashing. These layers are what actually keep water out; shingles are the first line of defense but not the only one. Cutting corners on these materials is the fastest way to create leaks that show up months or years later, after water damage has already begun.
When to hire a professional roofer
Roof installation is physically demanding work done at height on a sloped surface. If you are not comfortable working at heights, have a steep roof (over 8:12 pitch), or lack the tools and experience, hiring a professional is the safer choice. A roofer can complete the job faster, has insurance if something goes wrong, and can spot problems with the deck or structure that an untrained eye might miss.
Professional roofers also understand local building codes and can handle permit requirements. If your roof has complex features — multiple valleys, dormers, or unusual shapes — a professional will produce a better result and a longer-lasting installation. The cost of hiring someone is usually recovered in the durability and quality of the finished roof.
Frequently Asked Questions
Can I install new shingles over old ones?
Most building codes allow one layer of shingles over existing material, but it is not recommended. Layering creates an uneven surface, traps moisture, and makes it harder to spot problems with the deck. Removing old shingles takes more time but produces a better result and longer roof life. Check your local code before deciding.
How long do asphalt shingles last?
Standard asphalt shingles last 15 to 20 years in most climates. Architectural or laminated shingles last 20 to 30 years. Lifespan depends on climate, ventilation, and maintenance. Roofs in hot climates or with poor ventilation wear out faster. Regular inspections and prompt repairs extend the life of any roof.
What is the best time of year to install a roof?
Spring and fall are ideal because temperatures are moderate and the weather is usually stable. Avoid winter (shingles become brittle and hard to work with) and summer heat (the adhesive strip activates too quickly, making shingles difficult to position). Work on a dry day regardless of season — wet shingles are slippery and the underlayment will not adhere properly.
Do I need to remove gutters before installing shingles?
You do not have to remove gutters, but you should protect them from debris and nails. Cover the gutter with plywood or cardboard before you start, and be careful not to drop tools or nails into them. If gutters are old or damaged, consider replacing them at the same time as the roof — the cost is lower when the roof is already off.
What should I do if I find rot or soft spots in the roof deck?
Stop work and replace the damaged section before installing shingles. Cut out the soft area with a circular saw, then cut a piece of plywood to fit and nail it in place. The new section should be the same thickness as the surrounding deck. If rot is extensive, the roof structure may have other problems — consider having a professional inspect before proceeding.