Roof shingle installation is a multi-day job that requires safety equipment, proper technique, and attention to weather
Installing shingles yourself is possible if you have roofing experience, but it is physically demanding and genuinely dangerous. You will work at height, use a nail gun, and make decisions about water sealing that affect your home's protection for years. Most homeowners hire a contractor for this work. If you are doing it yourself, you need a safety harness, a roof ladder or brackets, proper footwear, and clear weather for at least two days. The actual nailing and overlapping follows a specific pattern that varies slightly by shingle type and roof pitch.
This guide covers the process so you understand what the work involves, can spot problems in a contractor's work, or can attempt it if you have construction experience. Mistakes here — wrong nail placement, poor overlap, nails driven at the wrong angle — lead to leaks that may not show up for months or years.
Key Takeaways
- Roof shingle installation requires safety equipment including a harness, roof ladder, and proper footwear, and should only be attempted by people with roofing or construction experience.
- Shingles are nailed in a specific pattern with precise overlap and nail placement; nails driven too high, too low, or at the wrong angle will fail during wind or rain.
- The job takes two to four days depending on roof size and pitch, and cannot be done safely in rain or high wind.
- Starter shingles go on first along the eaves, then full shingles layer upward in overlapping rows, with each row offset to break the seams.
- Mistakes in nailing, overlap, or flashing around chimneys and vents are the most common causes of premature roof failure and water damage.
Gather materials and safety equipment before you start
You will need the shingles themselves — order 10 percent extra to account for waste and mistakes — plus roofing nails (typically 1.25 inches for standard shingles), a pneumatic or cordless nail gun, a roofing hammer, a utility knife, and a chalk line. You also need a roof ladder or roof brackets to prevent sliding, a safety harness rated for fall protection, work gloves, and shoes with good grip. Many people rent a roof ladder from a tool rental shop rather than buy one.
Check the weather forecast before you commit to a start date. You cannot install shingles in rain, and wet shingles are slippery and harder to work with. Wind above 10 to 15 miles per hour makes the work unsafe and can blow shingles off as you nail them. Plan for two to four days depending on your roof size and pitch — steeper roofs take longer and are more dangerous.
Before you begin, inspect the roof deck (the plywood or boards under the old shingles). If it is soft, rotted, or sagging, it must be repaired or replaced before new shingles go on. Water damage to the deck means the problem is bigger than a shingle job.
Remove old shingles and prepare the roof surface
If you are replacing shingles, you must remove the old ones first. Use a pry bar to lift the shingles and break the seal created by the adhesive strip on the back of each shingle. Work from the top down, removing nails as you go. This is slow, repetitive work and creates a lot of debris. Rent a dumpster or arrange for debris removal before you start.
Once the old shingles are off, inspect the roof deck for damage, soft spots, or rot. Replace any damaged plywood. Check that the roof has proper ventilation — soffit vents and ridge vents or gable vents — because poor ventilation causes premature shingle failure and ice dams in winter.
Sweep the roof clean and install or replace the underlayment — a water barrier that goes between the deck and the shingles. Underlayment is typically a synthetic or felt material stapled to the deck. It catches water that gets under the shingles and directs it to the gutters. Do not skip this step even if the old roof did not have it.
Install starter shingles along the eaves and rake edges
Starter shingles are a full-width shingle with the tabs cut off, or a shingle installed upside down. They go along the bottom edge of the roof (the eaves) and the side edges (the rake). The starter row creates a solid base for the first course of regular shingles and fills the gaps between the tabs of the first row.
Snap a chalk line 11 and 3/8 inches up from the eave edge — this is where the bottom of the first course of regular shingles will sit. Install starter shingles along the eaves with the adhesive strip facing up, nailing them with four nails per shingle. The nails should be 5/8 inch from the top edge and spaced about 12 inches apart. Do the same along the rake edges (the sloped sides of the roof).
Make sure the starter shingles are straight and aligned. If they are crooked, the entire roof will be off. Use the chalk line as your guide and adjust as you go.
Nail the first course and establish the pattern
The first course of regular shingles goes on top of the starter row, aligned with your chalk line. Most asphalt shingles have four nailing spots marked on the back, or you can follow the adhesive strip as a guide. Each nail should go through the shingle and into the roof deck, not just into the starter shingle below.
Nail placement is critical. Nails should be driven straight, not at an angle, and should sit flush with the shingle surface — not so deep that they tear the shingle, and not so shallow that they stick up. A nail driven too high will miss the adhesive strip and fail in wind. A nail driven too low will puncture the shingle below and create a leak point. Most nail guns can be adjusted for depth; test on a scrap shingle first.
Offset each course so that the seams do not line up vertically. A common pattern is to cut the first shingle of the second row in half, so the seams stagger. This prevents water from running straight down through the seams. Continue this offset pattern as you work up the roof.
Work upward in overlapping rows with proper offset
Each new row of shingles overlaps the row below by about 5 inches, which means the tabs of the lower row are covered by the upper row. This overlap is what makes the roof waterproof. If the overlap is too small, water can get under the shingles. If it is too large, you waste shingles and the roof looks uneven.
Snap a new chalk line for each row to keep the shingles straight. The line should be 5 inches below the top of the tabs on the row below. Nail each shingle with four nails, placed in the same position on every shingle. Work from left to right or right to left, and maintain consistent spacing and overlap as you go up.
As you approach the ridge (the peak of the roof), you will need to cut shingles to fit. Measure the remaining distance and cut shingles to size with a utility knife. The last row at the ridge is typically a partial shingle.
Install ridge cap shingles and seal flashing around penetrations
Ridge cap shingles cover the peak of the roof where the two slopes meet. These are typically cut from regular shingles or come as pre-made ridge caps. They overlap at the peak and are nailed on both sides so that each nail is covered by the next shingle. Nail ridge caps with two nails per shingle, placed high enough that they will be covered by the next cap.
Flashing — metal or rubber strips that direct water around chimneys, vents, and other roof penetrations — must be sealed properly. Flashing should be installed under the shingles on the uphill side of the penetration and over the shingles on the downhill side. Seal the edges with roofing cement or a compatible sealant. This is where most roof leaks start, so take time to get it right.
Once the shingles and flashing are installed, walk the roof and check for any nails that are sticking up, shingles that are not sealed down, or gaps in the flashing. Press down any shingles that are not adhered, and seal any gaps with roofing cement.
Common mistakes that lead to roof failure
Nails driven at the wrong angle or in the wrong spot are the most common cause of premature shingle failure. Nails that miss the adhesive strip or are driven too high will not hold the shingle down in wind. Nails that are driven too deep will tear the shingle and create a leak point. Use a nail gun with depth adjustment and test it on scrap shingles before you start.
Poor overlap is another frequent problem. If the overlap is less than 5 inches, water can get under the shingles. If you cut corners on overlap to save shingles, you are creating a leak waiting to happen. Measure and snap chalk lines for every row.
Flashing mistakes — gaps, improper sealing, or flashing installed on top of shingles instead of under them — account for many roof leaks. Water finds its way to flashing and follows it into the home if it is not sealed properly. Take extra time around chimneys, vents, and skylights.
Frequently Asked Questions
Can I install shingles over old shingles without removing them?
You can in some cases, but it is not recommended. Old shingles hide damage to the roof deck, and the extra weight stresses the structure. Most building codes allow only one layer of re-roofing, and many roofers will not warranty work done over old shingles. Removing old shingles takes time but gives you a chance to inspect and repair the deck.
What is the right nail size for roof shingles?
Standard asphalt shingles use 1.25-inch roofing nails. The nail must be long enough to penetrate the roof deck (typically 3/4-inch plywood) by at least 3/4 inch. Using nails that are too short means they do not grip the deck, and nails that are too long can puncture the shingles below or stick through the deck into the attic.
How do I know if my nail gun is set to the right depth?
Test it on a scrap shingle placed over a piece of plywood. The nail should sit flush with the shingle surface — not sticking up and not sunk so deep that it tears the shingle. Adjust the depth setting and test again until the nail sits right. Check the setting periodically as you work, because air pressure changes can affect it.
What should I do if it rains while I am installing shingles?
Stop work when ready. Wet shingles are slippery and dangerous, and water can get under shingles that are not fully sealed. If rain starts, cover the exposed roof with tarps to prevent water from getting under the shingles you have already installed. Wait for the roof to dry completely before you continue.
Do I need to seal the nails on roof shingles?
No. Modern asphalt shingles have an adhesive strip on the back that seals around the nails when the shingle is warmed by the sun. The adhesive activates in heat and bonds the shingle to the one below, sealing the nail holes. In cold weather, this takes longer — sometimes several days. Do not walk on the roof or explore pressure to the shingles until the adhesive has set.