Replacing a shingle roof is one of those projects that looks straightforward from the driveway. Strip the old shingles, lay down new ones, nail them off, and you are done. Anyone who has done more than a handful knows how unforgiving the details can be. The surface might look clean when you pack up the ladders, but months later, a small oversight becomes a stained ceiling, a curled ridge line, or a warranty you cannot use. The money you “saved” disappears into repeat trips, callbacks, and indoor repairs.
This guide pulls from what tends to go wrong on roof shingle installation and roof shingle replacement jobs, especially when speed and price drive decisions. If you plan to do the work yourself, this will help you avoid traps. If you are hiring a shingle roofing contractor, this gives you the right questions to ask and the red flags to watch for.
Skipping the full tear-off when the deck is suspect
Overlaying new shingles on an existing shingle roof can work under narrow conditions. The roof has to be flat, dry, and free of soft spots, the existing shingles uniformly flat, and the structure must be able to carry the added weight. That last part is not trivial. A second layer of asphalt shingles adds roughly 200 to 300 pounds per square for common architectural shingles. On a 20-square roof, you are adding 4,000 to 6,000 pounds. Most truss systems can carry it, but you need to be sure.
Where overlays go bad is when the deck beneath is compromised. Years of minor condensation, prior leaks that never quite evaporated, or poor attic ventilation rot the top edges of the decking right under the shingle https://fernandoboux928.iamarrows.com/how-to-read-a-shingle-roofing-contractor-s-estimate joints. Put new shingles over that and you trap moisture, dull fastener bite, and telegraph every wave and hump. I have pulled two-layer roofs where my roofing spade went straight through the decking like crackers. The owner thought they were saving money by avoiding disposal fees. The cost showed up two years later when shingles started slipping off because nails had nothing firm to hold.
If you see shingle cupping, isolated dips between rafters, or hear hollow spots when you walk the field, strip it. Tear-offs take time, but they pay for themselves by letting you replace bad OSB or plywood, re-nail loose decking to code spacing, and start dry. A clean deck makes every piece that follows perform as designed.
Neglecting underlayment and ice barriers
Underlayment is not optional. It is the secondary water shed if wind drives rain up the laps or a shingle breaks loose. For years, roofers used felt reliably. It still works in dry climates where winter ice is not a problem and code allows. In most places, a synthetic underlayment resists tearing during install, lays flatter, and does not absorb moisture. The brand matters less than proper coverage, lap, and fastener spacing.
The bigger failure I see is skipping ice and water shield in the right places. If you have winters with freeze and thaw cycles, water backs up behind gutters and under the first few courses. That is predictable, not a fluke. A peel-and-stick membrane along the eaves, typically at least 24 inches inside the warm wall, gives that area a waterproof layer. Valleys, sidewall step flash zones, skylight perimeters, and dead valleys need it too. Use it there even in warm climates, because valleys concentrate water during hard rain and sideways wind.
Installers sometimes stop the membrane short of the warm wall because it saves a roll. Later, a January cold snap pushes thawed meltwater under the laps and into the top of the exterior wall. You do not see it until spring when paint flakes and drywall joints hairline crack. The fix is ten times harder than rolling membrane farther during the roof shingle installation.
Valleys: weaving trouble or exposing fasteners
Valleys move more water per foot than any other part of the roof. They also collect debris. Sloppy valley work shows up quickly. A woven valley can be appropriate on certain architectural shingles and lower slopes, but it requires full manufacturer guidance and practice to keep courses tight. A closed-cut valley with underlayment and a centered ice and water shield is more forgiving and looks cleaner.
The subtle mistake is driving nails too close to the valley centerline or cutting the shingle too tight. If you place nails within 6 inches of the cut line, you create a water path to a fastener. If you cut the top shingle flush to the valley, water sticks and rides under the course. I have pulled valley cuts with rusted nail heads right at the edge, every one a pinhole. Water does not need much of an invitation.
Leave a clean 2 inch to 3 inch valley exposure on a closed cut, keep nails 6 inches or more off the centerline, and stagger the cut ends so you do not line up seams. If you install metal open valleys, use prefinished or painted steel or aluminum, hem the edges, and avoid exposed fasteners in the water course. Some pros add a “W” valley to split the flow and reduce overflow during downpours. It costs a bit more and pays off on steep, large planes.
Short nailing, high nailing, and overdriven nails
Fasteners hold the roof together in wind. Most shingle warranties specify nail count per shingle, nail placement, nail length, shank type, and head size. Ignore those details and you void the wind rating. I have seen entire courses lift after a storm because nails were set just above the nail line, which means they never caught the doubled-up bond between overlapping shingles.
Short nails are common on overlays or thicker decking where folks assume a 1 inch roofing nail is enough. Through two layers of shingles and 5/8 inch decking, that nail might barely poke through, which translates to weak pullout strength. Use 1 1/4 inch nails for most single-layer installs on standard decking, and longer if you have thicker sheathing or a recover.
Overdriven nails slice through the mat, especially on hot days when compressors run high. The head cannot clamp the shingle if it is driven like a finish nail. If you are using a nail gun, set the pressure with a test strip and check it throughout the day. Hand nailing slows you down, but it teaches proper feel. Either way, nail in the designated line, use the required count, and confirm you are catching both layers where specified. It is not busywork, it is the difference between a roof that sheds water and one that peels.
Starter course mistakes that invite wind and wicking
Starters seem trivial until the first wind event. The starter shingle near the eave is not a random cut-off piece turned upside down. It needs a factory seal strip at the edge that aligns with the bottom of the first course. Without the strip in the right place, wind catches the bottom square of the shingle and flips it up. Once it lifts a few times, dust and granules stick to the tar line and it never bonds well again.
I see two common errors. One, using field shingles as starters without cutting off the tabs and seal strip location, which offsets the tar line by an inch or two. Two, failing to extend the starter over the drip edge by a half inch, so water wicks back under in heavy rain. That is when fascia gets stained and soffit joints swell. Use dedicated starter shingles or cut field shingles precisely per the manufacturer’s detail, align the sealant, and run them at both the eave and the rake edges. Many installers skip rake starters, and that omission shows up as edge lift on gable ends.
Flashing shortcuts at walls, chimneys, and penetrations
Shingle roofs do not fail in the field as often as they fail at transitions. Flashing is where craftsmanship shows. The three sins are reusing old flashing that is already work-hardened or corroded, face-nailing counterflashing instead of cutting a reglet, and burying step flashing into mortar or siding without proper laps.
Step flashing should be individual pieces for each course, not a long continuous L bent to run the whole wall. Each step should overlap at least 2 inches, with the vertical leg behind the siding or counterflashing and the horizontal leg on the shingle. Roofers who try to save time by running a continuous strip create a single point of failure. Water gets behind it at one spot, and capillary action drives it downhill inside the wall.
Chimneys deserve extra caution. They move slightly with temperature changes and settle differently than the roof structure. Install a cricket upstream on chimneys 24 inches or wider to split water around the sides. Wrap the base with step flashing, then install a counterflashing that tucks into a cut kerf in the mortar joint or brick, sealed with an appropriate masonry sealant. Smearing a fat bead of caulk along the base is not flashing, it is a temporary patch. That caulk hardens and cracks in a year or two and now you have water inside the chase.
Vents and pipe boots have their own pitfalls. The rubber boot material degrades under UV. On roofs with longer expected life, use higher-grade silicone boots or metal flashings with replaceable gaskets. Center the boot on the pipe, slide it under the upper course, and never face-nail the top edge. If your area sees snow load, consider ice saddle caps on larger vents to prevent ice dams from breaking the seal.
Poor attic ventilation and the moisture trap
Shingles fail early when the attic cooks them from below or steams them in winter. Adequate ventilation extends shingle life, preserves sheathing, and improves comfort. The rule of thumb most codes still lean on is 1 square foot of net free vent area for every 150 square feet of attic floor. That can be reduced to 1:300 when you balance intake and exhaust, but the ratio is less important than real airflow. Intake at the soffit brings in cooler air, ridge vents or box vents exhaust the hot air at the peak. Without intake, the best ridge vent does very little.
Common mistakes include installing ridge vent without cutting a wide enough slot, blocking soffit vents with insulation baffles, mixing ridge vent with power fans that short-circuit the airflow, and placing box vents too low on the slope. You also see bathroom fans dumping into the attic, which drives moisture into the insulation and roof deck. Every winter, I see frost build on nails, then melt and drip as stained rings on ceilings. Tie bath and kitchen fans to dedicated ducts that terminate outside with proper hoods and dampers.
Manufacturers quietly factor attic temperature into warranties. Some will prorate or deny claims if ventilation was not present as specified. Your shingle roofing contractor should measure and recommend the mix, and show you how they verify intake is clear. If they wave it off as unnecessary, that is a red flag.
Wrong shingle for the slope or climate
Shingles are not one-size-fits-all. Low slopes near the minimum for asphalt shingles, often 2:12 to 4:12 depending on the product, require special underlayment and tighter laps. On a 3:12 roof, rain lingers longer and wind can drive it upslope under the tabs. Many manufacturers require a full ice and water shield across the entire low slope area or a double underlayment method. Ignore that, and expect leaks even if every nail hit the line.
Climate matters too. Dark shingles on a south-facing, low-pitch roof in a hot climate will age fast. In the desert, I have replaced roofs at 12 years that looked 25 years old because the attic had minimal airflow and the shingle color and pitch trapped heat. In coastal zones, salt and high winds punish cheaper three-tab shingles. For high wind areas, confirm the wind rating on the shingle and install the extra nails called for. If you live where wildfires are a risk, Class A fire-rated shingles and underlayments are worth the small premium.
Hail zones deserve mention. Impact-resistant shingles carry a UL 2218 rating. They do not make a roof hail-proof, but they reduce bruising that shows up as granule loss and cracked mats months later. Home insurers in many states offer discounts for impact-rated shingles that can offset some of the upcharge.
Misaligned courses and lazy layout
A shingle roof looks like a grid, but it behaves like a system. Align your first course wrong, and by the time you reach the ridge, your reveal is drifting, your keyways line up, and water paths open between tabs. I have seen five-inch reveals creep to six on one side and drop to four on the other because the crew never snapped lines, they ran by eye.
Snap control lines at key points across the field, especially on larger planes and long runs. Check square against the eave and the rake. Follow the manufacturer’s offset pattern for the brand and style, since the laminate pattern of architectural shingles changes how joints stack. Staggered joints are not just for looks, they prevent channels for water to march under the exposure.
It is tempting to “make up” for a crooked course by narrowing the exposure quickly. That fix stands out from the yard. Better to break the course, correct early, and eat a few extra shingles than to live with an obvious drift for decades.
Reusing old flashing and vents to save a few dollars
It feels frugal to keep “perfectly good” metal flashing and attic vents. The problem is you rarely see hairline corrosion, bent flanges, or compromised gaskets until you have stripped the roof and flexed those parts. Driving new nails through old holes creates a path for water, and you change the pressure and shape on something that has already lived one life. More than once, I have been called back to fix a leak on a roof I did not install, only to find brittle pipe boots reused and spray-painted to look new.
Replace step flashing, counterflashing when accessible, pipe boots, vents, and exhaust caps during a roof shingle replacement. If you have copper or high-quality chimney flashing in excellent shape, you can carefully integrate it with new shingles, but test its integrity. Saving $200 on reused parts while installing a $12,000 roof is a poor bet.
Neglecting drip edge and edge metal
Drip edge directs water into gutters and protects the edges of the decking from wicking. In older neighborhoods, you still run into roofs without any edge metal. The plywood edge turns to sponge over time, fascia boards warp, and ice backs up underneath. When you replace the roof, install drip edge at eaves and rakes, under the underlayment at the rake and over the underlayment at the eave, per most modern details. Over gutters, make sure the drip edge reaches into the gutter bores, not behind them. A small gap between the gutter back and fascia invites water to run behind the gutter, which shows up as lines on the siding.
Choose a heavier gauge if you are in a windy zone. I have chased more rattles than I can count where thin, oil-canning edge metal hums in a gale. A slightly thicker profile quiets that down and resists deformation when ladders lean on it.
Ignoring manufacturer instructions and voiding warranties
Every brand has its own nailing zones, starter details, low-slope instructions, and ventilation requirements. Crews often assume all laminated shingles install the same. They do not. That matters when a storm pulls half the south face and an adjuster shows up. If the field lacks the required nail count or placement, you can lose warranty coverage and even insurance support in some disputes.
I keep the install sheet or package wrapper handy for the first day of a new brand or model. On one job, the manufacturer required six nails per shingle for the warranty wind rating even though the local code only required four. The homeowner called after a wind gust had peeled a ridge. We were covered because our photos showed the nailing pattern and the packaging. Document the process. If you are the homeowner, ask your shingle roofing contractor to photograph key steps: underlayment, valley prep, nail lines, flashing before siding goes back. It protects everyone.
Overlooking deck prep and fastener pull-through
Once the old shingles are off, the roof deck tells its story. You should see tight, flat panels with good nail retention. If you find delamination on OSB, soft spots where your boot sinks, or seams that open wider than a nickel, fix them. Replace bad sheets, add blocking where edges are unsupported, and re-nail sheathing to framing with ring-shank nails at proper spacing, often 6 inches on edges and 12 inches in the field, or per local code. Old homes sometimes have plank decking with gaps. That can work with shingles, but wide gaps need fill strips or overlay sheathing to create a solid nailing bed. Nails that miss framing leave divots and air paths.
A good deck prep also includes sweeping clean. Even a thin layer of granules under underlayment can create bumps that telegraph up through shingles. Debris under the membrane creates wear points. It is unglamorous work that never shows in photos, but it makes the roof last.
Underestimating safety and weather windows
Rushing a roof shingle repair or full replacement into a sketchy forecast sets you up for tarp gymnastics at midnight. Shingles will seal best when installed in moderate temperatures, typically above 40 to 50 degrees Fahrenheit depending on the product. Extreme heat softens mats and makes walking difficult without scuffing granules. Extreme cold causes cracking when you bend the tabs, and seal strips take much longer to activate, which leaves you vulnerable to wind until warmer days return.
Plan for the crew you have. A crew of three tearing off 18 squares won’t dry-in the same day unless the layout is simple and the run is efficient. Stage material thoughtfully so you do not overload one section of the roof or dump all the bundles over a garage where drywall seams pop from point loads. Stagger your tear-off so you can dry-in sections if weather shifts. I keep tarps and cap nails ready regardless of forecast, because storms build fast in summer and a half hour of sideways rain can ruin insulation and ceilings.
Leaving old satellite mounts, nails, and debris under the new work
It is easy to miss a hundred nails per square embedded in the old underlayment or driven into the deck. Those nails become pressure points that wear through from below. I run a magnet sweep over the deck, not just the yard. Old satellite mounts and wires should come off cleanly and holes sealed with proper methods, not caulk blobs. Penetrations you plan to abandon need real plugs. A 3/8 inch hole can channel surprising amounts of water in a storm.
After the roof is complete, run the magnet across the lawn and driveway again. Roofing nails in tires and paws create costs and bad blood that outlast the job. A clean site is part of a professional roof shingle replacement, not a courtesy.
Choosing a contractor on price alone
Price matters. So does margin, because roofing companies with no margin cut corners to survive. If two bids are far apart, dig into the scope. Does the lower bid include a full tear-off, new flashing, ice and water shield at eaves and valleys, ridge vent, and proper disposal? Are permits included? What is the shingle brand and model, and does the shingle roofing contractor hold the manufacturer’s installer credentials that enable extended warranties? Can they show proof of insurance, references, and recent jobs you can drive by?
I have been asked to “fix” new roofs that failed in a year. The owners bought the cheapest bid, which skipped ridge ventilation, reused flashing, and hired day labor with no supervision. The real cost of that first roof doubled once repair and legal headaches were tallied. A fair price includes time for site protection, careful details, and the inevitable curveball that shows up once shingles are off.
The quiet killers: small leaks that rot big structures
Not every leak announces itself with a drip bucket. Slow leaks around plumbing vents, sidewalls, or skylight corners can wick into framing and insulation. Over a season or two, they feed mold and rot that you only find when a painter scrapes a peeling exterior board or you step on a spongy spot on the second-floor landing. When we trace those, we often arrive at a small flashing mistake or a misnailed course.
After any roof shingle repair or replacement, walk the attic during a hard rain if it is safe. Look for shiny nail tips with droplets, dark rings around penetrations, or damp insulation. Use a moisture meter on suspect sheathing. Early fixes are cheap. Ignored, they lead to cut-out sections, rebuilt eaves, and sometimes structural repairs.
When a list helps: questions to ask before you sign
- What exact shingle brand, model, color, and wind rating will you install, and how many nails per shingle does that warranty require? Where will you use ice and water shield, and how far will it extend past the warm wall at eaves? Will you replace all step flashing, pipe boots, and roof vents, and how will you handle chimney counterflashing? How are you addressing attic ventilation, and can you calculate the intake and exhaust net free area for my roof? Can you show me photos of underlayment, valleys, nail lines, and flashing on a recent job, and will you document mine the same way?
A brief field story: the ridge that wouldn’t sit
A homeowner called about a “funny” ridge line. From the street, I saw a wavy shadow. Up close, the ridge cap sat proud by a half inch in places. The crew had installed ridge vent over a ridge that still had a double layer of decking from an old addition. They never cut a slot for the vent on that section, so air had no path and the vent floated. In the first wind storm, the cap tore at the high spots. The fix involved cutting the slot, replacing crushed vent sections, and reinstalling the cap with the correct nails and bead. That error came from rushing the layout and not checking the ridge thickness change along a complex roof. It is the sort of thing you catch when you slow down and walk the line before you nail anything permanent.
Maintenance after replacement: preserving the investment
Even a perfect install needs simple care. Keep gutters clean, especially if trees overhang the roof. Clogged gutters hold water at the eave, defeating drip edge and ice barriers. Trim branches that touch or overhang the roof, because constant abrasion wears granules and storms turn limbs into pry bars against shingles. After major wind or hail, scan the field for missing tabs, lifted ridge caps, or new granule piles at downspouts. Small roof shingle repair work early can prevent water from chasing underlaps and damaging decks.
If you add new penetrations later, like a solar conduit or a range hood, insist that the trades cut and flash properly, not rely on caulk. I have reworked dozens of brand-new roofs where a satellite installer shot lag bolts through shingles into decking without flashing, then smeared sealant. That kind of shortcut will always leak eventually.
The real economics of doing it right
Roofing budgets are real constraints, but the math favors detail. An average single-family roof in many regions falls between 15 and 30 squares. Better underlayment, full ice and water in critical zones, new flashing, and proper ventilation might add a few hundred to a couple thousand dollars depending on size and complexity. Spread over a 20 to 30 year service life, that difference is minimal. One leak that ruins a ceiling, a patch of hardwood flooring, and a few joists can chew through that savings in a weekend.
If you hire, choose a shingle roofing contractor who can explain their choices and is willing to show you work in progress. If you do it yourself, read the manufacturer’s instructions, snap lines, and resist the urge to cut corners as the sun drops. Your future self, dry and warm during a sideways rain, will be grateful.
A short homeowner checklist for the final walk-through
- Look at valleys for clean cuts, proper exposure, and no visible nails near the water path. Check that drip edge is installed at eaves and rakes, with tidy overlaps and integration with underlayment. Verify ridge vent has a continuous slot and even cap shingles, with correct nails. Confirm new flashing at sidewalls and around penetrations, with no blobs of caulk posing as permanent solutions. Ask for attic ventilation calculations and take a quick attic peek for daylight at the ridge slot and clear soffit baffles.
A shingle roof seems simple from ground level. The craft hides in the lines you cannot see and the laps that keep water moving the right way. Get those right, and the roof quietly does its job for decades. Get them wrong, and you pay for the mistake, often long after the truck pulls away.
Express Roofing Supply
Address: 1790 SW 30th Ave, Hallandale Beach, FL 33009
Phone: (954) 477-7703
Website: https://www.expressroofsupply.com/
FAQ About Roof Repair
How much should it cost to repair a roof? Minor repairs (sealant, a few shingles, small flashing fixes) typically run $150–$600, moderate repairs (leaks, larger flashing/vent issues) are often $400–$1,500, and extensive repairs (structural or widespread damage) can be $1,500–$5,000+; actual pricing varies by material, roof pitch, access, and local labor rates.
How much does it roughly cost to fix a roof? As a rough rule of thumb, plan around $3–$12 per square foot for common repairs, with asphalt generally at the lower end and tile/metal at the higher end; expect trip minimums and emergency fees to increase the total.
What is the most common roof repair? Replacing damaged or missing shingles/tiles and fixing flashing around chimneys, skylights, and vents are the most common repairs, since these areas are frequent sources of leaks.
Can you repair a roof without replacing it? Yes—if the damage is localized and the underlying decking and structure are sound, targeted repairs (patching, flashing replacement, shingle swaps) can restore performance without a full replacement.
Can you repair just a section of a roof? Yes—partial repairs or “sectional” reroofs are common for isolated damage; ensure materials match (age, color, profile) and that transitions are properly flashed to avoid future leaks.
Can a handyman do roof repairs? A handyman can handle small, simple fixes, but for leak diagnosis, flashing work, structural issues, or warranty-covered roofs, it’s safer to hire a licensed roofing contractor for proper materials, safety, and documentation.
Does homeowners insurance cover roof repair? Usually only for sudden, accidental damage (e.g., wind, hail, falling tree limbs) and not for wear-and-tear or neglect; coverage specifics, deductibles, and documentation requirements vary by policy—check your insurer before starting work.
What is the best time of year for roof repair? Dry, mild weather is ideal—often late spring through early fall; in warmer climates, schedule repairs for the dry season and avoid periods with heavy rain, high winds, or freezing temperatures for best adhesion and safety.