Common Causes of Asphalt Shingle Roof Blistering

Introduction

Asphalt shingles are among the most widely used roofing materials due to their affordability, durability, and ease of installation. However, one of the most common problems homeowners face with asphalt shingle roofs is blistering—the formation of raised bubbles or pockmarks on the surface of the shingles. While shingle blistering may not always cause immediate roof failure, it can significantly reduce the roof’s lifespan if not addressed. Below, we examine the leading causes of asphalt shingle blistering, how it affects the integrity of a roof, and the best ways to prevent and fix it.

What Causes Asphalt Shingle Blistering?

1. Poor Ventilation and Excessive Heat

Attic ventilation plays a crucial role in regulating temperature and moisture levels within the roofing system. When an attic lacks proper airflow, heat and moisture become trapped, causing shingles to overheat.

How It Affects Shingles: Extreme temperatures can cause trapped gases and moisture within the shingles to expand, forming blisters.
Signs of Poor Ventilation: Warm attic spaces, excessive humidity, and high cooling costs are indicators of inadequate ventilation.
Prevention Tip: Install ridge vents, soffit vents, or gable vents to improve airflow and reduce heat buildup.

2. Moisture Contamination During Manufacturing

Sometimes, asphalt shingles develop blisters before they are even installed due to manufacturing defects.

How It Happens: If moisture is present in the raw materials or trapped between layers during the production process, the shingles may form blisters once they are exposed to direct sunlight.
Prevention Tip: Choose high-quality asphalt shingles from reputable manufacturers and work with a professional contractor to ensure proper installation.

3. Improper Roof Installation

Incorrect installation techniques can contribute to shingle blistering.

Common Mistakes:
- Overdriven or misaligned nails that fail to secure the shingles properly.
- Inadequate underlayment, which fails to provide a moisture barrier.
- Stacking shingles improperly before installation, causing heat buildup and material distortion.
Prevention Tip: Hire an experienced roofing contractor who follows manufacturer guidelines and industry best practices.

4. Trapped Moisture Under the Shingles

When moisture accumulates beneath asphalt shingles, it can lead to thermal expansion, pushing trapped air pockets outward and forming blisters.

Sources of Moisture:
- Leaks from poor flashing or roof penetrations.
- Excess humidity rising from the interior of the home.
- Condensation forming in inadequately ventilated attics.
Prevention Tip: Ensure proper attic insulation and waterproofing measures to keep moisture from reaching the shingles.

5. Aging and Natural Wear

Over time, asphalt shingles naturally degrade due to exposure to ultraviolet (UV) rays, temperature fluctuations, and environmental pollutants. This degradation can cause the protective asphalt layer to break down, leading to blister formation.

How It Affects the Roof: Older shingles are more prone to blistering, and once the protective granules start to wear away, the roof becomes more vulnerable to cracks, leaks, and UV damage.
Prevention Tip: Schedule regular roof inspections and consider roof replacement when shingles approach the end of their lifespan (typically 20–30 years).

How to Identify and Address Blistering Shingles

Identifying Blistered Shingles

Blistered shingles appear as small raised bumps across the surface.
The blisters may remain intact or eventually pop, exposing the asphalt underneath.
Exposed areas will lose protective granules, accelerating roof deterioration.

Should You Be Concerned About Blistering?

If the blisters remain intact and the granules are not dislodged, they do not immediately impact the structural integrity of the roof. However, if the blisters pop, the underlying asphalt becomes exposed, leading to premature aging, increased UV damage, and water infiltration.

Steps to Prevent Further Damage

Monitor the roof for signs of blistering and check for popped blisters with exposed asphalt.
Avoid walking on blistered shingles, as foot traffic can cause blisters to pop.
Consult a professional roofer to assess the severity of the damage and recommend repair or replacement options.

Comparing Asphalt Shingle Blistering vs. Other Roofing Issues

Issue	Cause	Appearance	Risk Level	Prevention
Blistering	Heat, moisture, poor ventilation	Raised bubbles or pockmarks	Moderate	Improve ventilation, install quality shingles
Cracking	Aging, extreme weather	Split or cracked shingles	High	Regular maintenance, install flexible materials
Curling	Moisture, poor installation	Shingles curling upward at edges	High	Proper insulation, quality shingles
Granule Loss	Wear, hail, foot traffic	Bald patches on shingles	High	Avoid pressure washing, regular inspections

Roof Maintenance Tips to Prevent Blistering

1. Ensure Proper Attic Ventilation

Install ridge and soffit vents to allow air circulation.
Prevent heat buildup that causes shingle expansion.

2. Use High-Quality Roofing Materials

Choose moisture-resistant shingles from trusted brands.
Work with certified contractors for correct installation.

3. Keep Your Roof Clean and Inspected

Remove debris, leaves, and algae to prevent moisture buildup.
Schedule annual roof inspections to catch problems early.

4. Prevent Water Damage and Moisture Trapping

Ensure flashing and underlayment are installed correctly.
Fix roof leaks and clogged gutters to prevent excess moisture.

Trusted Roofing Experts

Asphalt shingle roofs require expert installation and maintenance to prevent common issues like blistering. Vera Roofing And Construction, located in Midlothian, TX, offers professional roofing services, ensuring high-quality materials and craftsmanship.

Our Certifications and Affiliations

GAF Master Elite Contractor
Firestone/Elevate Licensed Contractor for Commercial Roofs
A+ BBB Rating

We work with industry-leading brands, including GAF, Owens Corning, CertainTeed, Atlas, IKO, Firestone/Elevate, Mulehide, and F-Wave. Our commitment to integrity means we always deliver exceptional roofing solutions for every project.

Frequently Asked Questions

1. Are blistered shingles a serious problem?

Blistered shingles are not immediately dangerous unless the blisters pop, exposing the asphalt beneath. If granules are missing, the shingles will deteriorate faster.

2. How can I tell if my roof has poor ventilation?

Signs of poor ventilation include excess attic heat, condensation, and high energy bills. A professional roof inspection can determine if upgrades are needed.

3. Should I replace blistered shingles?

If the shingles still retain their granules, they do not need immediate replacement. However, if the blisters pop and expose the asphalt layer, replacement is recommended.

4. Can improper roof installation cause blistering?

Yes, incorrect installation techniques, including misaligned shingles, inadequate underlayment, and poor attic insulation, can contribute to blister formation.

5. How often should I inspect my asphalt shingle roof?

Roof inspections should be conducted at least once a year or after extreme weather events to check for blistering, granule loss, and other damage.

Conclusion

Blistering is a common issue in asphalt shingle roofs, but with proper ventilation, quality materials, and routine maintenance, homeowners can prevent significant damage. Ensuring correct installation and addressing moisture-related issues will extend the lifespan of a roof and protect it from premature deterioration. Professional roofing services can provide expert solutions to maintain a strong, durable roofing system.