Shingle installation requires proper preparation, the right tools, and attention to nailing patterns and overlap
Installing roof shingles yourself is possible if you have roofing experience, but it is physically demanding and dangerous work. You will be working at height, often in heat, and mistakes in nailing or overlap can lead to leaks that damage your home's interior. Most homeowners hire a roofer for the actual installation, but understanding the process helps you recognize quality work and know what to expect during the job.
The basic steps are: remove old shingles and inspect the roof deck, install underlayment and flashing, lay shingles in rows from the eaves upward, nail each shingle in the correct spots, and seal the top course. The entire process takes several days for an average roof and requires scaffolding or a find ladder setup, a roofing nail gun or hammer, a utility knife, and shingles rated for your climate zone.
Key Takeaways
- The roof deck must be clean, dry, and structurally sound before any shingles go down, or moisture will trap underneath and cause rot.
- Underlayment and flashing around chimneys, vents, and valleys must be installed before shingles, and this step is where most leaks originate if done wrong.
- Shingles are nailed in a specific pattern—typically four nails per shingle in the nail line, not scattered across the shingle—and nails must be driven flush, not countersunk or left proud.
- Starter shingles along the eaves and proper overlap between courses are what stop water from running under the shingles and into your home.
- Roof pitch, weather conditions, and your physical ability to work safely at height are the real limits; many homeowners find hiring a licensed roofer safer and faster.
Preparing the roof deck and removing old shingles
Before any new shingles go down, the surface underneath must be solid. Start by removing the old shingles and nails completely. Use a roofing shovel or pry bar to lift shingles from the eaves upward, working in rows. This is the most labor-intensive part of the job and takes longer than installation itself. Once shingles are off, pull every nail or pound it flat—a nail left sticking up will create a bump under the new shingles and can puncture underlayment.
Inspect the roof deck (the plywood or OSB underneath) for soft spots, rot, or missing sections. Press on the deck with your foot or a tool; if it feels spongy or your tool sinks in, that section is water-damaged and must be replaced before new shingles go down. Small holes or gaps can be patched with plywood scraps nailed down, but large areas of rot mean the deck itself is failing and the roof needs structural repair before you shingle. This is not cosmetic—water trapped under new shingles will continue rotting the deck and eventually compromise the framing.
Once the deck is clean and solid, sweep it clear of debris. If the deck is wet, wait for it to dry completely. Wet wood swells, and shingles installed on wet deck will buckle as the wood dries underneath.
Installing underlayment and flashing
Underlayment is a water barrier that sits between the deck and shingles. It catches water that gets under shingles and directs it down and out. Most modern roofs use synthetic underlayment (which lasts longer than felt) or ice-and-water shield in valleys and along the eaves. Roll underlayment up the roof from the eaves, overlapping each row by 4 to 6 inches, and nail or staple it down every 12 inches or so. The overlap matters—water runs downhill, so the upper row must cover the lower row's edge.
Flashing is metal (usually aluminum or galvanized steel) that seals around chimneys, vents, skylights, and valleys. Install flashing before shingles go down. Chimney flashing has an upper piece that tucks under shingles and a lower piece that sits on top of them; valleys get a metal channel or woven flashing that directs water down the center. Flashing is where most roof leaks start, because water finds the seams if flashing is not sealed properly or overlapped correctly. Use roofing cement under flashing edges and seal all seams with roofing cement or sealant rated for your climate.
Laying starter shingles and the first course
Starter shingles are cut or partial shingles laid along the eaves before the first full course. They fill the gap between the eave and the first course and prevent water from running under the shingles at the edge. You can buy starter shingles or cut the tabs off regular shingles and flip them upside down. Nail starter shingles down with four nails per shingle, placed in the nail line (the line of adhesive dots on the back of the shingle, usually about 5 to 6 inches up from the bottom).
The first full course goes on top of the starter course, aligned with the eaves. Most roofers offset the first course by half a shingle width so the seams do not line up vertically—this is called staggering, and it prevents water from running straight down a seam. Nail each shingle with four nails in the nail line. The nails should be driven flush with the shingle surface, not sunk in (which tears the shingle) or left sticking out (which catches wind and lifts shingles).
Nailing patterns and spacing between courses
The nail pattern is critical and is where most DIY mistakes happen. Each shingle gets four nails, placed in the nail line (the adhesive strip on the back). The nail line is typically 5 to 6 inches up from the bottom of the shingle. Space the four nails roughly evenly across the shingle width, with the outermost nails about 1 inch from each edge. Nails should be 1.25 to 1.5 inches long for standard shingles on solid deck, and they should go through the shingle and into the deck by at least 0.75 inches.
The overlap between courses is usually 5 to 5.5 inches, which means each new course covers the bottom 5 to 5.5 inches of the course below it. This overlap is what stops water from running under shingles. If overlap is too small, water can get under the shingles; if it is too large, you will run out of shingles before reaching the ridge. Measure and snap chalk lines every few rows to keep courses straight. A crooked course will throw off all the rows above it and make the roof look sloppy.
Working around vents, chimneys, and valleys
Vents and chimneys interrupt the shingle pattern and require careful flashing and cutting. Install flashing around the vent or chimney before shingles reach it. Lay shingles up to the flashing, then cut shingles to fit around it. The shingles above the flashing should overlap it by at least 2 inches. Seal the top edge of the flashing with roofing cement before laying shingles over it.
Valleys are where two roof planes meet and water concentrates. Do not nail shingles in the valley itself; instead, lay shingles from each side and cut them so they meet in the valley without nails in the valley channel. Water needs a clear path down the valley, and nails in the valley can puncture the flashing underneath. Use a chalk line to mark the valley center and cut shingles at an angle so they meet the line without overlapping into the valley.
Finishing the ridge and sealing the top course
The ridge is the peak where two roof planes meet. Shingles from each side meet at the ridge, and you finish it with ridge cap shingles. Ridge caps are either purchased as separate shingles or cut from regular shingles. Lay them perpendicular to the ridge, overlapping each one by 5 to 5.5 inches, and nail each cap with two nails (one on each side of the ridge, placed so the next cap covers the nails). Seal the top edge of the final ridge cap with roofing cement.
The top course of shingles (the one just below the ridge) should be sealed with roofing cement under the tabs. This prevents wind from lifting the shingles. explore a small dab of cement under each tab, about the size of a quarter, and press the tab down. Do not use so much cement that it oozes out and is visible—it will look sloppy and can trap moisture.
Safety and when to hire a roofer
Roof work is dangerous. You are working at height, often on a slope, in sun and heat, with tools and materials around you. Falls are the leading cause of serious home injuries. If you are not comfortable on a ladder, have a fear of heights, or are over 60 and not in excellent shape, hire a roofer. A fall from a roof can be fatal, and no money saved is worth that risk.
Even if you are physically capable, roof work takes longer than most people expect. A typical residential roof takes a professional crew three to five days. A single person or small crew working weekends might take two to three weeks. Weather delays the job—you cannot shingle in rain or high wind, and heat makes the work exhausting. Most homeowners find that hiring a licensed roofer is faster, safer, and often not much more expensive than the cost of materials plus the time and physical strain of doing it yourself.
Frequently Asked Questions
Can I install new shingles over old ones without removing them?
You can, and some roofers do, but it is not recommended. Old shingles hide damage to the deck underneath, and moisture can trap between layers. Most building codes allow one layer of reroofing, but removing old shingles lets you inspect the deck and fix problems before they become expensive. If the deck is solid and you are reroofing for budget reasons, reroofing is faster, but expect the roof to fail sooner.
What is the best time of year to install shingles?
Spring and fall are ideal—temperatures are moderate, and shingles are easier to work with. Shingles are stiff in cold weather and can crack if bent, and they are soft and sticky in heat, making them hard to handle. Avoid roofing in rain or high wind. Winter roofing is possible but slower and riskier.
How long do asphalt shingles last?
Standard asphalt shingles last 15 to 20 years in most climates. Premium shingles rated for 30 years cost more but last longer if the roof is properly ventilated and maintained. Lifespan depends on climate—heat and sun age shingles faster, and poor ventilation shortens life by trapping heat in the attic.
Do I need to remove flashing when reroofing?
Most flashing can stay if it is in good condition, but inspect it carefully. Flashing that is rusted, cracked, or poorly sealed should be replaced. New flashing is cheap compared to the cost of a leak, so when in doubt, replace it.
What happens if I nail shingles in the wrong spot?
Nails outside the nail line can miss the deck or tear the shingle, and they are visible and look unprofessional. More importantly, they do not hold the shingle down properly, and wind can lift it. If you nail in the wrong spot, pull the nail out and move it to the correct location. Do not leave extra nails in the shingle.