identifying asphalt shingle defefcts

Identifying Asphalt Shingle Roofing Defects

Whether you have a new roof or an aging roof, regular inspections and maintenance extend its life. Plus, a working knowledge of your roofing materials prevents insurance companies and roofers from taking advantage of you. The most common type of shingles in the United States are asphalt shingle roofs. So, we’ve created this guide to help with Identifying Asphalt Shingle Roofing Defects.

Asphalt Shingles 101

Before you can identify their defects, you’ll need to understand a little about asphalt roof shingles. Most shingles are about 3 feet long and 1 foot wide. However, modern premium shingles are slightly larger. Once installed on a roof, it isn’t easy to see where one shingle starts and ends. But if you look closely, you can see the ends.

All shingles have a concealed section and an exposed section. The exposed portion of one shingle overlaps the concealed area of the lower shingle. This overlapping pattern protects the nail heads and creates a waterproof barrier.

Granules make up the pebble-like coating embedded in the shingle. These shingle granules offer protection from physical damage and UV radiation. Plus, they make the shingles look nicer and grippier for walking on.

If you lift the shingle, you’ll see the nails, an adhesive strip, and possibly a nailing strip. The adhesive strips bond two layers of shingles together to prevent wind damage. They may be on the bottom or top of the shing. Once installed, the shingles heat up, and the adhesive strips melt and bond.

Once the adhesive strip sets, lifting the shingles is not easy. Although you could break the seal with a putty knife, I would not recommend it unless necessary. And if you do break the seal, make sure to reseal it with roofing cement.

Some shingles, like the one in the photo, have a reinforced nailing zone to enhance wind resistance. Otherwise, the nailing zone is almost always below the adhesive strip. Nails Installed in the nailing zone go through two layers of shingles – the layer you drive the nail through and the layer underneath.

Anatomy of a Shingle

anatomy of an asphalt shingle

3-Tab Asphalt Shingles Vs. Dimensional Shingles

Identifying which type of shingle you have helps estimate the remaining lifespan. For the most part, there are two main types of shingles – three-tab asphalt shingles and laminated asphalt shingles. Laminated shingles also go by architectural, dimensional, laminated architectural, laminated dimensional, or really any combination of those three words.

3-tab shingles aren’t that common anymore due to the superior quality, lifespan, and price of laminated shingles. However, flippers and cash-strapped owners may still opt for a 3-tab shingle roof.

On 3-tab shingles, the exposure is three separate tabs, giving this shingle its name. Plus, they’re flat and uniform in appearance. If you’ve ever seen a house with a very orderly, grid-like shingle pattern on the roof, it’s likely 3-tab shingles.

Conversely, dragon teeth give laminated/dimensional shingles their multi-dimensional appearance. Plus, they’re thicker, heavier, and more robust than 3-tab shingles.

Now, we’re ready to go over some common asphalt shingle problems.

infographic comparing 3-tab shingles vs. laminated shingle

1. Adhesive strip failure

Self-adhesive strips (tar strips, seal strips) are the most critical aspect of your roof’s wind resistance. They seal down the leading edge of the shingle to prevent uplift from the wind. Unfortunately, the adhesive strips sometimes fail long before the shingles fail. Additionally, since they require several days in the heat to activate, installation in cold temperatures can cause failure.

Once the adhesive strips fail, the shingles are more prone to storm damage from high winds and other defects.

The fact that most shingle manufacturers only provide 5-year wind warranties is a revealing clue about the lifespan of these adhesive strips.

You should not be able to lift the edges of the shingles. If you can lift the shingles, the self-adhesive strips are failing or have failed. The only remedy is to hand seal any affected shingles with roofing cement. Although you could leave them as is, resealing them will extend the lifespan of your roof.

identifying failed adhesive strips

2. Moss Growth on Asphalt Shingles

Moss (and lichens) may look pretty on your roof, but they’re quietly wreaking havoc. Although there is some disagreement about whether moss deteriorates shingles, it’s clear that moss causes roof damage and leaks. This is because moss grows under the shingles and pushes them up, making them prone to wind damage and leaks.

So, a little moss probably won’t hurt at first. However, left untreated, water damage, mold, and expensive repairs are inevitable. It’s pretty easy to clean moss off your roof. But it’s best left to the professionals if you’re scared of heights.

Zinc strips or sprays are a promising solution if you have a chronic moss and lichen problem.

this moss on the roof can cause damage and needs to be cleaned

3. Algae Growth

Identifying the difference between moss and algae on your roof is easy yet often neglected.

Algae growth presents as a black discoloration on your roof. Homeowners and many home inspectors mistake algae for moss or mold. And many roof cleaners and roofing contractors perpetuate the myth that it damages roofs. Fortunately, industry leaders such as ARMA maintain that there is no evidence to suggest that algae are harmful to a roof. If the appearance bothers you, spray the roof with a bleach mixture or other proprietary cleaners. 

algae is not bad for a roof

4. Asphalt Shingle Blistering

Blistering has two different appearances – intact and popped. Intact blisters look like pimples or little bumps on the shingle’s surface. Popped blisters look like little craters.

While manufacturing defects are a potential cause, poor attic ventilation is always a cause. In other words, a manufacturing defect may be a contributing factor, and poor attic ventilation would be the catalyst. Poor attic ventilation increases the attic temperature, thus increasing the temperature of the underside of the shingles. Shingles baking in the summer heat need attic ventilation to help cool them off, or they’ll overheat, bubble, blister, and pop.

If the blisters are still intact, then this issue is primarily cosmetic. However, if the blisters are popped, the shingles will deteriorate much quicker, leading to further damage. In either case, blistering indicates you need to improve your attic ventilation. If there is a widespread blister popping, it’s a good idea to talk to a roofing company about replacement.

infographic shingle blisters

5. Identifying Shingle Hail Damage

Hail damage is a prevalent issue in some areas. If you’ve never experienced a hail storm, identifying roof hail damage or problems may not be a skill you’ve developed. It’s often confused with blistering, but they’re pretty different in nature.

Roof Hail Damage:

  1. Impact Marks: Depending on size and velocity, Hailstones can cause various types of damage. You may observe dents, dings, or small divots where the hail has impacted the shingle.
  2. Loss of Granules: A fresh hail hit can remove the granules (the small, grainy protective coat on the shingle) from the impact spot. This may expose the underlying asphalt layer, which can look dark/black in contrast to the surrounding granules.
  3. Random Distribution: Hail damage is typically randomly distributed across the roof, based on the trajectory and size of the hailstones during the storm.
  4. Other Damages: Hail can also damage other parts of a home, such as gutters, siding, and vents. If you notice dents or other signs of impact on these elements, it’s a good indication that the roof damage may also be from hail.

Roof Blister Pops:

  1. Raised Bumps: Blistering is caused by moisture or air trapped in the shingle during the manufacturing process. Over time, heat causes these blisters to expand and eventually pop. They often appear as small bumps or raised areas on the shingle before they pop.
  2. Loss of Granules: When a blister pops, it can also cause the loss of granules, but unlike hail damage, it doesn’t have the accompanying impact indentation.
  3. Uniform Distribution: Blister pops tend to be more uniformly distributed across a roof due to manufacturing issues. If you notice repetitive patterns or a consistent spread of these popped blisters, it’s more likely a blistering issue rather than hail damage.
  4. No Other Damages: Since blistering is a shingle-specific issue, you won’t see accompanying damage on gutters, siding, or other parts of the house.

If you suspect hail damage, call your insurance company before calling a roofer. They will likely send out an insurance adjuster to evaluate the damage before approving an insurance claim.

infographic blister pops vs hail damage on asphalt shingles

6. Craze Cracking

Asphalt Shingle Craze Cracking refers to the fine, superficial, network-like pattern of cracks that can appear on the surface of an asphalt shingle. The name is apt, as the cracks form a “craze” pattern, similar to the cracking seen on old pottery or glazed ceramics. This is not to be confused with deeper, more structural cracks that may compromise the shingle’s integrity.

Causes of Craze Cracking:

  1. Aging: Over time, exposure to the elements (like the sun’s UV rays) can cause the shingles to dry out. As the volatile compounds in the shingle evaporate or degrade, the shingle loses flexibility. This can lead to the development of craze cracks.
  2. Manufacturing Defects: If shingles are manufactured with an improper or inconsistent asphalt formulation, it can make them more susceptible to craze cracking.
  3. Thermal Stress: Asphalt shingles are exposed to daily and seasonal temperature fluctuations. Over time, the repeated expansion and contraction due to these changes can lead to the development of craze cracks.
  4. Mechanical Stress: Improper installation techniques or walking on the shingles during extremely hot or cold temperatures can induce stress, leading to this kind of cracking.
  5. Poor Ventilation: Roofs need proper ventilation to manage moisture and temperature. A poorly ventilated roof can trap heat, accelerating the shingle aging process and making craze cracking more likely.

It’s essential to note that while craze cracking is mostly a cosmetic issue, it indicates the aging of the shingle. Over time, a roof with extensive craze cracking may become more susceptible to other forms of damage or wear. If you observe these cracks, it’s a good idea to keep an eye on the roof’s overall condition and consider consultation with roofing professionals for an evaluation.

identifying asphalt shingle craze cracking

7. Curling Roof Shingles

Asphalt Shingle Curling is a phenomenon where the edges of the shingles curl upwards or downwards, away from the roof deck. When shingles curl, they can no longer perform effectively as a barrier against the elements, making them less effective at shedding water and more susceptible to wind uplift.

Causes of Asphalt Shingle Curling:

  1. Aging: As asphalt shingles age, the materials can dry out and lose their flexibility. Over time, this can cause the shingles to shrink and curl. This is the most common cause of shingle curling.
  2. Poor Ventilation: Proper attic ventilation helps regulate temperature and moisture levels in the roof deck. Without adequate ventilation, excessive heat and moisture can build up, accelerating the deterioration of the underside of the shingles and causing them to curl.
  3. Improper Installation: Shingles need to be correctly nailed down. If nailed too high or with insufficient nails, they may not be adequately anchored, leading to curling. Similarly, not following the manufacturer’s instructions for shingle alignment and spacing can result in curling.
  4. Manufacturing Defects: Sometimes, defects in the manufacturing process can lead to shingles that are more prone to curling. If a particular roof’s curling problem doesn’t seem to have an external cause, it might be due to a manufacturing defect.
  5. Wet or Damaged Roof Deck: If the wood decking beneath the shingles is damp or damaged, it can cause the shingles to warp and curl.
  6. Multiple Roof Layers: Installing new shingles over old ones (rather than stripping the roof down to the deck) can result in uneven surfaces. The new shingles may not lay flat, leading to premature curling.
  7. Thermal Shock: Extreme and rapid temperature changes can cause “thermal shock” in shingles, leading to accelerated aging and curling.
identifying curling asphalt shingle

7. Identifying Asphalt Shingle Manufacturer Defects

Manufacturing defects in shingles can compromise a roof’s longevity, functionality, and appearance. There are generally no specific defects that are definitely manufacturing defects. Instead, you’re looking for patterns and ruling out installation as a cause. For example, if defective shingles are in one specific section of the roof, this may indicate only that batch/pack was bad. So, if you have any type of damage, take a closer look for tell-tale signs of defective shingles.

Possible Manufacturer Defects

  1. Granule Loss: If a shingle loses its granules (the textured, grainy surface) prematurely, it could be due to poor adhesion during manufacturing. Look for inconsistent, bare patches or a significant amount of granules in the gutters or at the base of downspouts.
  2. Blistering: Blisters are raised areas or bubbles on the shingle’s surface. They can form if moisture or air is trapped in the shingle during manufacturing. While small blisters may not immediately compromise the shingle’s functionality, larger ones or those that pop can leave the shingle vulnerable.
  3. Misaligned Laminate Layers: On laminated or architectural shingles, if the top and bottom layers aren’t appropriately aligned during manufacturing, it can lead to issues like water seepage.
  4. Thickness Inconsistency: Uneven thickness across the shingle or from one shingle to another can indicate a manufacturing defect. This inconsistency can affect the shingle’s performance and lifespan.
  5. Craze Cracking: While craze cracking can be due to aging or environmental factors, if it appears on relatively new shingles, it might indicate a manufacturing defect, possibly from an improper asphalt mixture.
  6. Misshapen Shingles: If shingles are not uniform in shape or have uneven edges straight out of the package, it’s likely a manufacturing issue.
  7. Faulty Adhesive: The adhesive strip on the shingle, responsible for bonding overlapping shingles together, can sometimes be improperly applied or missing altogether. It might be a manufacturing defect if shingles don’t adhere correctly or if the adhesive strip is misaligned.
  8. Differential Weathering: If shingles age or fade unevenly in areas that receive the same amount of sunlight and weather exposure, the inconsistency might be due to variations in shingle quality or composition during manufacturing.
  9. Improper Cutouts: There should be uniform cutouts for certain types of shingles like 3-tab. If these are inconsistent or misaligned, it’s a clear sign of a manufacturing defect.

If you suspect a manufacturing defect in your shingles:

  1. Document Evidence: Take clear photos and make notes of any flaws you find. Keeping a record can be useful for warranty claims or discussions with roofing professionals.
  2. Check Warranty: If your shingles are under warranty, manufacturing defects are often covered. Familiarize yourself with the warranty terms and reach out to the manufacturer.
  3. Consult a Professional: If you’re unsure about potential defects or their severity, it’s wise to consult with a roofing contractor. They can provide a more thorough inspection and advise on the next steps.
  4. Retain Product Info: Always keep the packaging or information labels when installing new shingles. This can provide essential details about the product batch and manufacturing date, which can be crucial for warranty claims.
identifying common problems with asphalt shingle roofs

8. Other Shingle and Defects

There are many other types of shingle damage, such as missing shingles, bald spots, boot damage, and other intentional damage. Most of these are easy to spot and don’t require a working knowledge of asphalt shingle roofing.

When in doubt, always call a professional home inspector for your roofing inspections. Unlike roofers, home inspectors have no reason to sell you on repairs you don’t need.

And never schedule a free roof inspection. Offering free roof inspections is a strategy used by roofers to drum up business (sell roofs).