Common Problems Found with Asphalt Shingle Roofs

Asphalt shingle roofs are the most common roofing type in North America, valued for their cost-effectiveness and reliability. However, even these durable roofs can develop issues that home inspectors frequently encounter. Below we outline several common asphalt shingle problems – from manufacturing defects to installation mistakes – explaining how each issue arises and what it means for roof performance and longevity. This information can help homeowners and buyers understand roofing defects noted in inspection reports and why they matter.

Manufacturing Defects and “Batch” Problems

Manufacturing defects in asphalt shingles are relatively rare, but they do occur. These defects originate from errors in the shingle production process – for example, insufficient asphalt coating, contaminants or moisture trapped in the material, or improper curing of the fiberglass mat. Such hidden flaws create weak spots in the shingle that may not be obvious at installation, but will deteriorate faster under weather exposure. Over time, affected shingles age and fail prematurely, sometimes causing mysterious roof leaks that are hard to trace (since the damage is systemic rather than isolated).

One specific phenomenon is “batch problems.” Shingles are made in batches, and if shingles from different manufacturing batches are mixed on one roof, they can weather at different rates. As the roof ages, sections from one batch may deteriorate faster than adjacent sections, creating a telltale stair-step pattern of decay that follows the installation pattern. This uneven aging becomes apparent near the end of the shingles’ warranty period. Notably, batch-related failures are often natural aging differences rather than a true factory defect in the material, but the effect is similar – parts of the roof wear out sooner than others. In any case, widespread manufacturing or batch defects can shorten the roof’s service life. If discovered within the warranty window, homeowners may have recourse with the manufacturer; otherwise, localized repairs or even early roof replacement might be needed if large areas are compromised.

Blisters in Shingles (Heat Bubbles)

Blistering is a common asphalt shingle issue characterized by small pimple-like bumps on the shingle surface. Blisters form when moisture or volatile oils become trapped within the shingle layers (usually in the asphalt coating) and then vaporize and expand under heat. The pressure from the trapped gas pushes up a little bubble under the granule surface. Blisters often develop during hot summer weather, especially on newer shingles within the first year or two of installation.

What causes the trapped moisture? In many cases, blistering traces back to manufacturing conditions – if the shingle materials were slightly damp or not fully cured, small amounts of moisture can be sealed into the shingle at the factory. Later, sun heat causes that moisture to expand and form blisters. Excess use of asphalt roof cement (such as during installation or repairs) can also cause blisters by adding solvents that get absorbed into the shingle. However, poor attic ventilation is “always a cause” as well. Inadequate ventilation allows heat to build up under the roof, essentially baking the shingles from below. This extreme heat can “flash” moisture and volatile compounds out of the asphalt, producing blisters even in well-made shingles. In other words, even quality shingles may blister if a hot attic cooks them continuously.

Intact vs. popped blisters: A blister may remain unbroken (just a raised bump with granules intact on top), or it may eventually pop, shedding the granule coating in that spot. Intact blisters are mostly a cosmetic issue and do not immediately compromise waterproofing. In fact, because most asphalt shingles have multiple layers (especially laminated architectural shingles), an un-popped blister usually doesn’t penetrate all the way through the shingle layers. However, popped blisters leave little crater-like pockmarks where the protective granules are gone and the asphalt substrate is exposed. These spots will age and deteriorate much faster under UV sunlight and weather. A cluster of popped blisters effectively thins the roof’s protective layer, which can lead to accelerated granular loss, asphalt cracking, and potentially leaks if the damage progresses.

Implications: The presence of many blisters is a red flag. While a few isolated blister pops can be patched or might be harmless, widespread blistering is a sign of trouble. If an entire slope is peppered with popped blisters, the roof may wear out years earlier than its intended lifespan. Extensive blistering often coincides with ventilation problems, so an inspector will likely recommend improving attic ventilation to prevent recurrence. If blister-related granule loss is severe, roof replacement may be necessary to restore full protection. At minimum, expect a blistered roof to require extra monitoring and maintenance. It’s also worth noting that blisters are sometimes confused with hail damage – but an inspector can distinguish them by their uniform distribution and lack of impact dents (see Hail Damage below).

Improper Bonding/Sealing of Shingles

Asphalt shingles are designed with a factory-applied self-sealing strip – an asphalt-based adhesive that softens in warm weather and bonds each shingle tab to the one below it. Proper sealing is what makes the roof wind-resistant. When this bonding fails to occur, shingles remain loose. Improper sealing is typically an installation or weather-related issue (not a material defect), and it is a serious concern: unsealed shingles can lift or even blow off in high winds, opening the roof to leaks.

Common causes of bonding failure include:

• Cold Weather Installation: If shingles are installed during cold or winter conditions, they may never reach the temperature needed for the sealant to activate. The strips usually require a few days of warm sunshine to fully bond. Shingles put down in late fall or winter might remain unsealed until spring – and if an unusually cold, cloudy season follows, some shingles might not seal for many months. During that time, they are vulnerable. In fact, manufacturers explicitly warn that unsealed shingles are prone to blow-offs and wind damage, and that this situation is a function of weather, “not a manufacturing defect”. (Roofers often hand-seal shingles with dabs of roofing cement in cold weather as a precaution.)

• Debris or Surface Contamination: The bonding can also fail if something prevents the adhesive from contact. Dust, dirt, or tree debris on the shingle can keep the sealant from sticking. Likewise, if a roofer overdrives nails through a shingle, it can create a hole or bump that breaks the seal. Mishandling of the release film is another culprit – shingles come with a plastic strip to prevent sticking in the bundle; normally it is left in place, but if it’s removed at the wrong time and gets stuck on the sealant area, that section won’t adhere.

• Insufficient Heat or Alignment: In some cases, a shingle might be slightly misaligned or warped such that the sealant strip doesn’t touch the mating shingle properly. Or, a stretch of cool, cloudy weather right after installation could delay sealing. If the roof pitch is very steep, gravity can also hinder the shingles from laying flat to bond (manufacturers recommend hand-sealing on very steep slopes or high-wind areas).

Consequences: When shingles do not bond, the most immediate risk is wind damage. Strong gusts can lift unsealed shingle tabs and crease or tear them, or rip shingles off entirely since the wind can get under them easily. Even a moderate wind may cause unsealed shingles to flutter, breaking the watertight seal and allowing wind-driven rain to penetrate. Repeated lifting also tends to work nails loose over time. In short, the roof’s wind resistance is drastically reduced. If unsealed areas are extensive, a storm can peel up large sections of the roof. In less dramatic cases, you may simply see shingle tabs sticking up or “flapping” on a windy day. Those loose tabs invite water infiltration at the next rain, particularly if wind-blown rain gets underneath them.

If an inspector finds many loose shingles that can be easily lifted by hand, it will be noted as a defect. The remedy might be to hand-seal each unbonded shingle with roofing cement (a labor-intensive process) or, if the problem is widespread and systemic, the shingles might need reinstallation or replacement. Fortunately, once shingles do seal, they are very secure – so this is primarily a concern on relatively new roofs or immediately after installation. Homeowners should be aware that if a new roof was installed in cold weather, it may not be storm-ready until warmer weather allows the seals to set. Checking for proper adhesion the following season is a wise idea.

Buckling Shingles (Warping or Wavy Appearance)

Buckling refers to shingles that warp out of their flat plane, creating a wavy, rippled, or lifted appearance on the roof surface. Buckled asphalt shingles often have a distorted, wrinkled look – they may arch upward in a vertical hump or have a series of ripples. This is distinct from “curling,” which usually means the edges of individual shingles curl up or down (often from age or moisture in the shingle itself). Buckling involves larger sections of the roof looking uneven.

What causes buckling? The root cause is almost always movement or unevenness in the roof deck or underlayment beneath the shingles. Key reasons include:

• Moisture in the Roof Deck: If the wood sheathing (deck) got wet before or during roof installation, it can later dry out and shrink or shift. Plywood or OSB panels can swell when wet and then contract, moving shingles out of place. This often shows up as buckling aligned with the panel joints or rafters. Similarly, dimensional lumber roof boards (found in older homes) will expand and contract with moisture changes. If adjacent boards move, they can cause the shingles above to buckle along those lines. Inadequate attic ventilation exacerbates this by allowing moisture buildup in the decking.

• Inadequate Sheathing Gaps: Modern roof sheathing should be installed with a small gap (about 1/8") between panels to allow for expansion. If the plywood/OSB was butted too tight with no gap, the panels can push against each other and buckle upward in humid conditions. This telegraphs through the shingles as ridges or raised lines.

• Wrinkled Underlayment: Roofing felt or underlayment that was installed with wrinkles or that absorbed moisture can itself pucker up. Wrinkled underlayment causes random raised wrinkles in the shingles above. This type of buckling isn’t in straight lines (unlike deck-panel buckling) – it will appear as random waves across a roof face.

• Structural Movement: Although less common, if the house framing or trusses settle or move significantly (or in rare cases of earthquake or structural failure), it can create large buckles or dips in the roof. These are usually accompanied by other structural issues.

• Installation Issues: Shingles can also buckle from poor installation practices. If shingles were not allowed to acclimate and were installed in extreme heat, they might later contract and pull against nails. Overdriven or tilted nails can hold down one part of a shingle while the other part lifts (giving a buckled look). Additionally, if a new layer of shingles is applied over an old layer (overlay), any unevenness or debris beneath can cause the new shingles to buckle or not lie flat.

Why it matters: Buckled shingles are more than an appearance issue. When shingles are not lying flat, their integrity and weather resistance is compromised. Raised areas are more exposed to wind uplift. A strong wind can catch a buckled section and tear the shingle or cause nail pull-through. The distorted shingles also don’t seal as well – a shingle that’s tented up may not properly adhere to its neighbor, meaning the self-seal strip may not be effective. This further heightens the risk of wind damage.

Moreover, buckling indicates potential moisture problems in the roof system. Moisture-related buckling (from a wet deck or underlayment) often goes hand-in-hand with diminished roof life – the excess moisture can lead to wood rot, mold in the attic, or corrosion of fasteners. If buckling is due to an underlying leak or trapped moisture, that issue needs addressing or leaks could develop. Water can also intrude at the raised shingle edges. A buckled shingle might allow wind-driven rain to get blown under it, especially if the deformation has broken the seal.

In summary, buckling is both a symptom and a hazard. An inspector will usually point out buckled areas and suggest further evaluation of the roof decking and attic ventilation. Fixing buckling may involve removing affected shingles and any wrinkled underlayment, checking that the decking is dry and properly fastened, then reinstalling. If widespread, the entire roof might require replacement (particularly if caused by un-gapped sheathing, which is hard to fix piecemeal). Ignoring buckling can lead to ongoing water damage and even structural issues over time.

Cracking and Splitting of Shingles

Asphalt shingles can develop cracks over time, and in more severe cases, full splits. While often mentioned together, cracking and splitting describe different degrees of damage:

• Cracking: Cracks are thin, fracture lines in the shingle surface – essentially, partial-thickness breaks. They often appear as random hairline cracks or craze-cracking in the asphalt. The primary cause is aging and weathering. Years of UV exposure dry out the asphalt, making it less flexible and more brittle. Temperature fluctuations (hot days and cool nights, or seasonal freeze-thaw cycles) cause the shingles to expand and contract, which can produce stress fractures in the weakened material. Minor cracking may be localized to certain shingles or areas (commonly on south-facing slopes with more sun exposure). Early on, these cracks might be small and shallow, not all the way through the shingle. At this stage, they are largely cosmetic and may not immediately leak. However, multiple or growing cracks are a red flag – they indicate the shingle is losing its integrity. Eventually, cracks can widen or interconnect, dislodging granules and exposing the asphalt underneath. Even before leaks occur, extensive cracking means the roof’s useful life is nearing its end.

• Splitting: A split is a more severe break where a shingle tears completely through, often splitting it into two pieces (or nearly so). Splits can be linear or irregular openings that run across the shingle, sometimes even spanning its full length. This level of damage is often caused by extreme stress or defective shingle composition. One common scenario is “thermal splitting” seen in certain fiberglass shingles – rapid temperature swings cause the shingle to expand and contract beyond its capacity, resulting in long cracks/splits (particularly in older or thinner shingles). Manufacturing defects in some shingle batches (notoriously in the 1990s for fiberglass shingles) led to widespread thermal splits in those products. Aside from thermal stress, impact or wind can also cause splits – for example, large hail or a person walking on a brittle roof can crack shingles. Improper installation (such as high nailing or using shingles in cold weather when they’re inflexible) can create stress points that later split.

Consequences: Cracks and splits pose a direct risk to the roof’s water-shedding ability. A cracked shingle is thinner and can eventually let water seep through, especially if debris or wind pries the crack open. Water entering a crack can reach the shingle’s backing or the roof underlayment; in freezing weather that water can freeze and expand, prying the crack wider. Over time, even small cracks can lead to moisture intrusion and rotted decking if not addressed. Split shingles are an even bigger problem – a through-split is like having a hole in the roof. Leaking is almost guaranteed once a shingle is completely fractured, since nothing stops water from reaching the felt and deck below. For this reason, multiple cracked shingles or any splits are grounds for replacement of those shingles (or the whole roof if widespread). Roofing experts note that while a few isolated cracks might be repairable, split shingles usually require immediate replacement to prevent water penetration.

Another issue is that cracking and splitting often indicate an aging roof. For instance, if a significant number of shingles are cracking, the roof may be past its prime. One or two cracked shingles could be replaced, but if dozens are cracked, it may not be cost-effective to patch each one. Instead, that’s a sign the roof as a whole is failing. Indeed, professional guidance suggests that if cracked or brittle shingles are widespread, roof replacement is the prudent solution, as the integrity of the roof is at risk. An inspector will typically recommend replacing shingles that are cracked through, and if many shingles are affected, they’ll advise that the roof is near end-of-life.

In summary, cracks and splits reduce a shingle’s ability to keep water out. They tend to expand over time and can result in serious leaks and water damage inside the home. Homeowners should keep an eye out for any cracking in their shingles, especially as the roof nears the 15-20 year mark or beyond. Early intervention (replacing a few shingles) can stave off bigger problems, but eventually, a cracked/split roof section must be redone for reliable protection.

Hail Damage to Asphalt Shingles

Hail storms can wreak havoc on an asphalt shingle roof in a matter of minutes. Hail damage on shingles typically appears as impact marks and areas of granule loss. When hailstones strike the roof, the force can dislodge the mineral granules that protect the shingle surface. A fresh hail strike often leaves a dark, round bare spot where granules have been knocked away, exposing the asphalt layer beneath. It may look like a bruise or dimples on the shingle. In some cases – especially with larger hail – the impact will also fracture the shingle mat. This might not create a visible hole immediately, but it cracks the reinforcement (fiberglass or organic mat) internally, which is referred to as a “bruised” shingle. A bruised shingle often feels soft or spongy at the impact point if pressed.

Several characteristics of hail damage include:

• Random Distribution: Hail hits are usually scattered randomly across the roof, not in a regular pattern. This differentiates them from blisters (which may be more uniformly distributed or aligned with shingles). Inspectors will note a random peppering of spots.

• Granule Loss and Dark Spots: As mentioned, the protective granule coating is often lost at the point of impact. The spots where granules are gone will appear as dark pockmarks (since the asphalt and underlying mat are typically dark). Finding lots of granules in gutters after a hailstorm is also a clue.

• Dents/Cratering: Depending on hail size, there may be visible dents or depressions in the shingles. Larger hail can leave quarter-sized or bigger dents that you can see and feel. The shingle may have a crushed look in those spots.

• No Pattern of Other Damage: With hail, one often finds collateral signs – dents in metal gutters, downspouts, AC units, or cars, etc. If the roof has spots and nearby metalwork is dinged up, hail is likely the cause. (In contrast, blistering won’t dent metal or vents.)

How hail damage affects the roof: In the immediate aftermath, minor hail impacts might not leak, especially if they only removed granules. However, the loss of granules is significant because those granules shield the asphalt from UV rays and physical wear. Exposed asphalt areas will degrade much faster under sunlight. The sun’s UV light can dry out the asphalt at the bruise, making it brittle and causing it to crack . Also, the spots where the mat is cracked (even if the crack doesn’t go all the way through yet) allow water to slowly infiltrate the shingle’s layers. Over time, water can seep into those micro-fractures. Repeated heating (sun) and cooling or freeze-thaw cycles will turn a bruise into a full-blown crack or “through fracture.”

In short, hail damage is an accelerating problem – what starts as a tiny pockmark can become a leak a year or two later. Research and field experience show that what might seem like merely cosmetic hail marks often lead to leaks after the shingles go through a few thermal cycles. For instance, a “bruised” area may develop a crack that runs through the shingle (especially if the hail was large). If a shingle is fractured completely by hail, that’s an immediate leak risk, akin to a split shingle.

Roof longevity and warranty: Hail damage shortens the roof’s lifespan. Even moderate hail can cause enough granule loss that a roof expected to last 20 years might only last 10 more. Manufacturers generally exclude hail (an “act of nature”) from warranty coverage because of its severe effect. In fact, impact-resistant shingles (rated Class 4 under UL 2218) are marketed in hail-prone regions specifically to resist this kind of damage. Standard shingles, when hit by hail, become vulnerable to UV and water at each impact spot. If a roof has widespread hail hits (insurance companies often use a threshold like X hits in a 10’x10’ area), it usually warrants full replacement. That’s because patching individual spots is impractical – there could be hundreds of impact points. Many homeowner insurance policies cover roof replacement for hail damage if it’s significant. So, if an inspector notes hail damage, the homeowner should check insurance and possibly have a professional roofing contractor assess it immediately.

In summary, hail damage may not cause instantaneous leaks during the storm, but it severely compromises the roof. Homeowners should be aware that even small-looking hail marks are points of future trouble: “seemingly insignificant impacts can still cause harm to underlying roof structures”. After any hail event, it’s wise to have the roof inspected. If damage is confirmed, taking action (repairs or replacement) sooner rather than later will prevent the compounded problems of water damage down the line.

Improper Installation Practices

Even high-quality shingles can fail early if they’re not installed correctly. Two of the most common installation errors that home inspectors encounter are poor nail placement and excessive shingle overhang beyond the eave. These mistakes can lead to a host of problems, from leaks to wind damage. Below, we explain these issues:

• Incorrect Nail Placement: Asphalt shingles must be nailed in the right location and with proper technique. Each shingle has a specified “nailing strip” (often indicated by a painted line) where nails should be driven. If nails are placed too high, the shingle is not securely fastened to the one below. This effectively halves the number of nails holding each shingle, since the nail misses the lower shingle. Shingles with high nailing can slide out or tear off because they’re only held by a couple of nails at their top edge. On the other hand, nails placed too low or exposed (visible on the shingle face) can invite leaks – water can rust out the nail or seep around it. Another issue is over-driven or angled nails. If a nail is shot in with too much pressure, it can punch through the shingle or crack the mat, leaving that shingle barely attached. Over-driven nails and skipped nails are a major cause of shingles blowing off in sheets during storms. The photo below illustrates proper vs. improper nailing:

  

  Figure: Nailing diagram – The proper nail zone (blue dots) secures both the shingle and the one below it. High nailing leaves the lower shingle unpinned, reducing wind resistance.

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  In short, bad nailing = weak roof. Shingles may initially lie flat even if mis-nailed, so the issue might not be visible until failure happens. But over time, improperly nailed shingles often develop slipped or “floating” tabs, or they blow off in moderate winds when they should have remained secure. If an inspector notes inappropriate nailing (perhaps observed from an attic where nails missed the rafters, or from a lifted shingle), they will recommend corrective action. Unfortunately, if an entire roof was nailed incorrectly, the only true fix is to redo the roofing because you can’t reliably re-nail shingles without damaging them. Manufacturers also void the warranty if shingles weren’t installed to their nail placement specs.

• Shingles Overhanging Too Far Past the Eave/Gutter: Shingles should slightly overhang the roof edge to drip water into the gutters, but too much overhang is a problem. If shingles extend excessively (beyond about 3/4" past the drip edge), they lack support underneath. The overhanging portion can flex and crack under its own weight or in high winds. In hot weather, unsupported overhanging shingles may sag or curl downward (sometimes you’ll see the leading edges curled over the gutter like a wilted leaf). Moreover, a big overhang creates a leverage point where wind can catch the shingle; the wind uplift can pry the shingle up and possibly rip it off at the edge. GAF (a major manufacturer) advises that shingles should not extend more than 3/4" past the edge, or else “they are not supported and may crack and break off” and additionally “the wind resistance at the roof edge may be compromised.”. In practical terms, if shingles overhang too far, you might find pieces of broken shingle on the ground along the roof line after a windstorm – the overhung bits snap off. Also, excessive overhang can cause water to miss the gutter: as water clings to the underside of a long shingle, it might drip behind the gutter instead of into it.

  Conversely, insufficient overhang (shingles cut too flush with the eave) is also an issue, since water can wick back onto the fascia. Most manufacturers recommend about a 1/2" overhang if a drip edge is present (and slightly more if no drip edge). But the key point is balance – too much overhang is a roofing flaw that can lead to edge damage. If found during an inspection, the solution can be tricky; short of trimming the shingle edges (which is not usually feasible once installed), one might install metal flashing or drip edge extensions to protect the vulnerable shingles. Ideally, the shingles should have been cut correctly initially. Edge strips or a careful application of roofing cement under the overhang can sometimes help keep them from lifting. However, if the overhang is extreme on a new roof, an owner should ask the installer to fix it, as it contradicts standard guidelines and could void wind-resistance warranty claims.

Other installation issues can include improper shingle alignment, inadequate stagger of joints, missing underlayment or flashing, etc. But the nailing and overhang problems discussed above are especially common and can dramatically affect roof performance. A roof that might have lasted 25+ years can fail in 10 if these basics are done wrong. That’s why reputable contractors and manufacturers emphasize following installation instructions to the letter. From an inspector’s standpoint, when such defects are observed, they will be noted because they predispose the roof to future problems (leaks, blow-offs, etc.). Homeowners buying a house with a relatively new roof should not assume the roof is perfect – if it was improperly installed, defects will surface sooner rather than later. Always address installation-related issues early, as they can often be corrected before resulting in interior damage.