Ensuring the quality of shoes is crucial for any manufacturer or retailer in the apparel industry. Poor quality leads to disappointed customers, damaged stock, and potentially lost business. Here are the five common shoe defects you should be aware of:

  • Opened Seam
  • Broken Stitches
  • Poor Cementing
  • Asymmetric Quarter Height
  • Yellow Transformation

Quality shoes not only increase customer satisfaction but also bolster the reputation of your brand. They prevent returns and reduce inventory delays, ensuring that customers come back for more.

By addressing these common defects, manufacturers can significantly improve their products and maintain a competitive edge in the market. Effective quality control measures help not just in identifying but also in solving these issues before they become costly problems.

We’ll delve into each of these common shoe defects and provide practical solutions to address them.

Infographic showing five common shoe defects - common shoe defects infographic pillar-5-steps

Opened Seam

An opened seam anywhere on the shoe can be a serious issue. It affects the shoe’s structural integrity, making it a critical defect in baby products and a major defect in other types of footwear. This type of defect can lead to the shoe falling apart, which is obviously a big problem for customers.


1. Wrong Thread
Using the wrong type of thread is a common cause of opened seams. If the thread is not strong enough to handle the tension during sewing, it can break easily.

Example: Imagine a baby shoe where the seam opens because the thread couldn’t withstand the stress. This is not just a quality issue, but a safety concern for the child.

2. Faulty Sewing Process
A faulty sewing process is another major cause. This can happen if the under thread is missing or too loose. Without proper support, the top seam can easily come apart.

Case Study: In one factory, inspectors found that several shoes had opened seams because the sewing machines were not correctly calibrated. This was quickly fixed by adjusting the machine settings and retraining the staff.

sewing machine issue - common shoe defects

3. Insufficient Glue
Sometimes, the issue is not just with the thread but also with the glue used in the bonding process. If the glue is insufficient or not applied correctly, it can lead to the seam opening up.

Tip: Always ensure that the right amount of glue is used, and that it is applied evenly to provide additional support to the seams.

By understanding these causes, manufacturers can take preventive measures to avoid opened seams. This includes using the right type of thread, ensuring proper sewing techniques, and applying sufficient glue.

Broken Stitches

Broken stitches are a major defect in shoe manufacturing. They compromise the structural integrity of the shoe, making it prone to falling apart. This defect can result in dissatisfied customers and increased returns. Let’s look at the main causes of broken stitches.


Accidental Cut or Burn

Sometimes, the thread gets accidentally cut or burned during the production process. This often happens when trimming the seam. If the thread is cut too close, it weakens the seam, leading to broken stitches.

Burned Thread

Threads can also burn during production. This can happen if the machine’s heat settings are too high. Burned threads become brittle and break easily, compromising the entire seam.

Production Machine Issues

Faulty sewing machines can also cause broken stitches. If the machine’s tension settings are incorrect, the thread may be too tight or too loose. This inconsistency can weaken the stitches, making them more likely to break.

Preventive Measures

To avoid broken stitches, manufacturers should:

  • Ensure proper machine settings: Regularly check and adjust the tension settings on sewing machines.
  • Use high-quality thread: Low-quality thread is more likely to break or burn.
  • Train workers: Ensure that workers are skilled in trimming seams without cutting the thread.

By addressing these causes, manufacturers can significantly reduce the occurrence of broken stitches, leading to higher quality shoes and happier customers.

Next, we will discuss poor or weak cementing and its impact on shoe quality.

Poor or Weak Cementing

Poor or weak cementing is a common shoe defect that can lead to significant issues, especially in shoes with rubber soles like sneakers. This defect often manifests as degumming, where the sole starts to detach from the upper part of the shoe. It’s a major defect because it affects the shoe’s structural integrity and overall durability.


Adhesive Failure

Adhesive failure happens when the glue used to bond the shoe components is not effective. This can be due to several factors:

  • Insufficient Glue: Not using enough adhesive is a primary cause. Without adequate glue, the bond between the shoe components is weak, leading to degumming. It’s crucial to apply the right amount of adhesive to ensure a strong bond.

  • Incorrect Pressure: During the cementing process, applying the correct pressure is essential. If the pressure is too low, the adhesive won’t bond properly. This is why pressure settings need to be monitored and adjusted as necessary.

  • Expired Glue: Using expired glue can also lead to adhesive failure. Expired adhesives lose their bonding properties, making them ineffective. Manufacturers should regularly check the expiry dates on glue containers to avoid this issue.

Minor Defect vs. Major Defect

While some adhesive issues might be considered minor, like excess glue marks, weak cementing is typically a major defect. Excess glue can be cleaned up post-production, but weak cementing compromises the shoe’s integrity and can result in returns and dissatisfied customers.

Preventive Measures

To prevent poor or weak cementing, manufacturers should:

  • Select the Right Adhesive: Ensure the glue used is suitable for the materials being bonded. Different materials require different types of adhesives.

  • Proper Application: Train workers to apply the right amount of adhesive and use the correct tools. Over-gluing can be as problematic as under-gluing.

  • Regular Checks: Perform adhesive strength tests before production and regularly check expiry dates on adhesives.

  • Consistent Pressure: Ensure that the machinery used to apply pressure is well-maintained and calibrated correctly.

By addressing these causes, manufacturers can significantly reduce the occurrence of poor or weak cementing, leading to higher quality shoes and happier customers.

Asymmetric Quarter Height

Asymmetric quarter height is a cosmetic deviation that occurs when the height of the rear portion of one shoe does not match the other. This defect can be classified as either a minor defect or a major defect, depending on the severity.


Fault During Lasting Process:
The most common cause of asymmetric quarter height is a fault during the lasting process. During this stage, the upper part of the shoe is stretched over the last (a mold that gives the shoe its shape). If this process is not done correctly, the shoe’s quarter height can become uneven.

Inconsistent Upper Allowance:
Another cause is inconsistent upper allowance. This means that the amount of material allowed for the upper part of the shoe is not uniform. When the upper material is not cut or sewn consistently, it can lead to differences in the height of the shoe quarters.

Minor Defect vs. Major Defect

  • Minor Defect: If the height difference is less than 2 mm, it is generally considered a minor defect. While this might not affect the shoe’s functionality, it can still impact the overall appearance and perceived quality.

  • Major Defect: If the height difference exceeds 2 mm, it is classified as a major defect. Such a visible deviation can make the shoes look low quality and can lead to customer dissatisfaction and returns.

Real-World Impact

Imagine a customer buying a pair of shoes only to find that one shoe’s quarter height is visibly different from the other. This not only affects the aesthetic appeal but also the brand’s reputation.


  • Quality Control: Implementing strict quality control measures during the lasting process can help identify and correct these issues before the shoes reach the customer.

  • Training: Ensuring that workers are well-trained in the lasting process and understand the importance of consistent upper allowance can significantly reduce the occurrence of asymmetric quarter height.

  • Regular Inspections: Conducting regular inspections and using standardized tools for measuring the height of the quarters can help catch any deviations early.

By addressing these causes and implementing effective solutions, manufacturers can minimize the occurrence of asymmetric quarter height, leading to better quality shoes and more satisfied customers.

Yellow Transformation


Yellow transformation is a discoloration defect that often impacts the soles of shoes, turning them yellow over time. This is considered a major defect because it can severely affect the shoe’s appearance and customer satisfaction.

Aging Material

One primary cause of yellow transformation is the aging of materials used in the shoe. Light-colored or transparent materials, especially thermoplastic polyurethane (TPU), are prone to this issue. As these materials age, they naturally start to yellow, which can make even a new pair of shoes look old and worn out.


Oxidation is another significant factor. When materials like TPU are exposed to air, they undergo a chemical reaction that results in a yellowish tint. This process is accelerated by exposure to light, especially sunlight, which can make the shoes look uneven and unappealing.

Older Material

Using older materials in the production process can also lead to yellow transformation. Manufacturers sometimes use leftover or outdated materials to cut costs, but this can backfire. Older materials are more likely to show signs of yellowing even before the shoes reach the consumer.

Light Exposure

Light exposure is a critical factor in yellow transformation. Shoes stored or displayed in well-lit areas, especially under direct sunlight, are at higher risk. This is why it’s crucial to store shoes in a controlled environment to minimize light exposure.

Understanding the causes of yellow transformation can help manufacturers take preventive measures, such as using fresh, high-quality materials and controlling storage conditions. By addressing these issues, the occurrence of yellow transformation can be significantly reduced, leading to higher customer satisfaction.

Next, we will discuss puckering and wrinkles and their impact on shoe quality.


Puckering and wrinkles in shoes are not just cosmetic issues; they can affect the overall appeal and perceived quality of the product. While they may sometimes be considered minor defects, they can easily become major defects if they are too noticeable or affect the shoe’s structure.


1. Lasting Process:
Puckering often occurs during the lasting process, where the shoe upper is stretched over the last (the mold that shapes the shoe). If the material isn’t stretched evenly or tightly enough, it can result in puckering or wrinkles.

2. Natural Wrinkles in Genuine Leather:
Genuine leather is a natural material, and it can have inherent wrinkles or imperfections. If these natural wrinkles are not identified and managed before production, they can lead to visible defects in the finished product.

3. Inconsistent Upper Allowance:
The allowance of the upper part of the shoe can be inconsistent during the lasting process. If the material is not properly aligned or tensioned, it can create puckering or wrinkles, especially in areas that require a smooth finish.

4. Faulty Handling:
Improper handling during various stages of production can also cause wrinkles. For instance, if the shoe is not stored or transported correctly, the material can develop creases that are difficult to remove later.

Impact on Quality:
While minor puckering or wrinkles might be acceptable in less visible areas (like the rear or bottom of the shoe), they are considered major defects if found on any prominent or visible part. This is because they can make the shoe look low quality and affect customer satisfaction.

To prevent puckering and wrinkles, manufacturers should ensure:

  • Proper tensioning during the lasting process
  • Using high-quality, well-prepared materials
  • Adequate training for workers to handle materials correctly
  • Regular inspections to catch and correct issues early

By understanding and addressing these causes, manufacturers can reduce the occurrence of puckering and wrinkles, leading to higher-quality shoes and happier customers.

Next, we will explore the issue of slanted heels and their impact on both aesthetics and safety in footwear.

Slanted Heel

A slanted heel is a major defect that impacts both the look and safety of a shoe. When a heel deviates from a 90° angle to the floor, it can be more than just a cosmetic problem. A significant slant can lead to sprained ankles and other injuries, especially with high heels.


Heel Assembly Fault: One primary cause of a slanted heel is an error during the heel assembly process. If the heel isn’t properly aligned or secured, it can lead to a noticeable slant.

Screw Issues: Another common cause is related to the screws used to attach the heel. If the screw is slanted or not fully tightened, the heel can become misaligned.

Quote: “A slanted heel not only ruins the aesthetic of a shoe but poses a serious safety risk. Ensuring proper heel assembly is crucial,” says a quality control expert from V-Trust Inspectors.


To prevent slanted heels, manufacturers should:

  • Ensure Proper Alignment: During heel assembly, make sure the heel is aligned at a perfect 90° angle.
  • Tighten Screws Correctly: Use the right tools and techniques to fully tighten screws, preventing slanting.
  • Regular Inspections: Conduct periodic checks during production to catch and correct any alignment issues early.

By addressing these causes, manufacturers can significantly reduce the occurrence of slanted heels, resulting in safer and more visually appealing shoes.

Next, we will delve into the issue of soles not being flat and how it affects the walking experience for the wearer.

Sole Not Flat

A flat sole is crucial for comfortable walking. When the sole isn’t flat, it can cause walking irregularities and discomfort for the wearer. Let’s explore the causes and classifications of this defect.


1. Poor Outsole Shape
A common reason for a sole not being flat is a poor outsole shape. This can happen due to:

  • Faulty Molds: If the molds used to shape the outsole are defective, the final product will be uneven.
  • Inconsistent Cutting: Inaccurate cutting of the outsole material can also lead to uneven surfaces.

2. Heating Process Deformation
During production, the outsole undergoes a heating process. Deformations can occur if:

  • Incorrect Temperature: If the temperature is too high or too low, the outsole can warp.
  • Uneven Heating: Inconsistent heating across the outsole can cause parts of it to expand or contract differently, leading to an uneven surface.


Minor Defect
A sole not flat is considered a minor defect if the gap between the sole bottom and the floor is less than 5 mm. While this may not be immediately noticeable, it can still affect the overall comfort and aesthetic of the shoe.

Major Defect
The defect becomes a major issue if the gap exceeds 5 mm. This not only looks unattractive but can also cause significant discomfort and walking irregularities for the wearer. In extreme cases, it may even lead to injuries.

Next, we will delve into the issue of detached rivets and how they impact the structural integrity of shoes.

Detached Rivet


A detached rivet is a serious issue that can significantly impact the structural integrity of a shoe. This defect is particularly concerning because it can lead to safety hazards, especially for children.

Major Defect

A detached rivet is always considered at least a major defect. If the rivet is likely to detach within a 36-month timeframe for baby shoes, it becomes a critical defect. This is due to the potential choking hazard it poses.

Insufficient Glue

One common cause of detached rivets is the use of insufficient glue. If the adhesive is not strong enough or not applied in the right quantity, the rivet may not hold properly. This can cause the rivet to detach over time, compromising the shoe’s structural integrity.

Weak Pressure

Another cause is weak pressure during the assembly process. If the rivets are not pressed together with enough force, they may not secure properly. Uneven pressure can also lead to some rivets being more likely to detach than others.

Testing for Detached Rivets

During pre-shipment inspections, a pull-gauge is often used to measure the strength of rivets. Applying 90 N of force for 10 seconds helps determine if the rivet can withstand normal wear and tear. If it detaches, it indicates a failure to last through 36 months, especially critical for baby shoes.

Next, we will explore the issue of peeling leather, tears, and other damage and their impact on shoe quality.

Peeling Leather, Tears, and Other Damage

Peeling leather, tears, and other surface damage are common shoe defects that can significantly impact the visual appeal and durability of footwear. These defects are usually classified based on their location and severity.


1. Scratched Upper

A scratched upper often results from the shoe rubbing against sharp points on production machines. This can occur during processes like the rubbing before outsole gluing or the lasting process. Scratches on the top, front, or sides of the shoe are considered major defects, while those on the back or bottom (and less than 2 mm in size) are minor defects.

2. Old Material

Using old or aged materials can lead to peeling leather. Over time, the coating on leather can deteriorate, causing it to peel off. This not only looks unattractive but also signals poor material quality, affecting the shoe’s overall durability.

3. Production Machine Issues

Poor maintenance of production machines can also cause surface damage to shoes. For instance, if the machinery used in the production line has worn-out parts, it can scratch or tear the shoe material. Regular maintenance schedules can help prevent such defects.

Cosmetic Flaw

While some surface damage may seem minor, it can still detract from the shoe’s visual appeal. For example, a small tear or peeling leather can make the shoe look old and poorly made, even if it doesn’t affect its functionality.

Major Defect

Surface damage on the top, front, or sides of the shoe is considered a major defect. This is because these areas are highly visible and significantly affect the shoe’s aesthetic and perceived quality. Customers are likely to return shoes with such defects, impacting sales and brand reputation.

Minor Defect

Damage on less visible areas like the back or bottom of the shoe, and less than 2 mm in size, is classified as a minor defect. While still a concern, these defects are less likely to result in customer dissatisfaction or returns.

Fact: According to industry standards, peeling leather or other surface damage on the top, front, or sides is a major defect, while similar damage on the back or bottom (and less than 2 mm in size) is minor.

Regular quality control and proper maintenance of production machinery are crucial in preventing these defects. Ensuring the use of fresh, high-quality materials can also mitigate the risk of peeling leather and surface damage.

Next, we will address frequently asked questions about common shoe defects to help you better understand these issues and their solutions.

Frequently Asked Questions about Common Shoe Defects

What is the common problem with shoes?

One of the most common problems with shoes is adhesive failure. This happens when the glue bonding the shoe components fails, causing parts like soles and uppers to come apart. Poor or weak cementing can also lead to this issue.

– Insufficient glue application
– Incorrect pressure during bonding
– Using expired glue

Solution: Ensuring the right type and amount of glue is used and applying it correctly can prevent adhesive failures.

What are minor defects on shoes?

Minor defects are small imperfections that don’t affect the shoe’s functionality but can still impact its overall quality and appearance.

Scuff marks: These are small scratches or marks, often seen on glossy or leather shoes.
Color variations: Slight differences in color that can occur due to inconsistent dyeing processes.
Cosmetic flaws: Small blemishes or imperfections that don’t affect the shoe’s performance.

Solution: Regular quality checks and proper handling during manufacturing and packaging can minimize these minor defects.

What is a flaw in a shoe?

A flaw in a shoe can be any defect that affects its appearance, durability, or performance. These can range from minor cosmetic issues to major structural problems.

Poor cementing: When the bonding between shoe parts is weak, leading to parts coming apart.
Broken stitching: This affects the shoe’s structural integrity and can result from using incorrect thread or faulty sewing processes.

Solution: Proper maintenance of production machines, using high-quality materials, and thorough inspections can help identify and fix these flaws before the shoes reach customers.

By understanding these common shoe defects and their solutions, manufacturers can improve the quality of their footwear and ensure customer satisfaction.


Quality control in shoe manufacturing is essential. It ensures customers receive products that meet their expectations and keeps your brand’s reputation intact. At NuShoe Inspect & Correct, we understand the impact of common shoe defects on customer satisfaction and business success.

We offer comprehensive quality control inspection services to help you identify and address defects before they reach your customers. Our experts inspect for issues like poor cementing, broken stitching, and peeling leather, ensuring your products meet the highest standards.

By investing in thorough quality control, you can minimize returns and complaints, saving both time and money. Happy customers are loyal customers, and they will spread the word about your reliable products.

In conclusion, paying attention to quality control not only safeguards your brand’s reputation but also boosts customer satisfaction and reduces returns. Let NuShoe Inspect & Correct help you deliver top-quality footwear every time. Contact us today to learn more about how we can assist you in maintaining the highest quality standards in your shoe manufacturing process.