Shingle blistering occurs when small, raised bumps or bubbles form on an asphalt shingle’s surface, typically caused by trapped moisture or gas within the shingle expanding and pushing outward as the roof heats up under direct sun exposure.
This condition can originate from moisture trapped during manufacturing, inadequate attic ventilation causing excess heat and humidity buildup beneath the roof deck, or in some cases installation over a damp roof deck that hadn’t fully dried before shingles were applied.
Once a blister eventually ruptures, often from foot traffic, hail, or simple aging, the granules covering that spot are lost along with the raised material, exposing the underlying asphalt at that specific location.
What Causes Shingle Blistering?
- Trapped moisture within the shingle from manufacturing
- Inadequate attic ventilation causing excess heat buildup
- Installation over a damp or inadequately dried roof deck
- Thermal cycling causing trapped gas to expand and contract
Why Is Shingle Blistering Important?
Once blisters rupture and expose the underlying asphalt, that specific area becomes vulnerable to accelerated deterioration and potential water intrusion, making blistering a genuine early warning sign worth investigating rather than a purely cosmetic curiosity. Identifying the underlying cause, whether inadequate ventilation or a manufacturing issue, matters for preventing the problem from affecting the roof more broadly.
Because inadequate attic ventilation is a common contributing factor to blistering, addressing ventilation balance alongside any necessary shingle repair can help prevent the same issue from recurring, particularly on roofs showing widespread rather than isolated blistering patterns. Addressing the root cause alongside any visible repair offers the best chance of a lasting solution.
Shingle Blistering vs. Shingle Buckling
Shingle blistering involves small, localized raised bumps from trapped moisture or gas. Shingle buckling involves a larger-scale wavy or rippled distortion across the shingle surface, often related to underlying deck movement rather than the more localized blistering condition.