Blistering on asphalt shingles typically appears as raised bubbles or bumps on the shingle surface and is usually caused by trapped moisture or air beneath the shingle granules. This can happen when shingles are exposed to heat and sunlight, causing moisture within the shingles to expand and form blisters. It may also result from manufacturing issues or improper ventilation in the attic, where warm, moist air doesn't escape, leading to moisture buildup under the roof covering. Over time, these blisters can crack, break down the shingle surface, and reduce the roof’s ability to protect your home from weather elements. A simple way to check for blistering yourself is to carefully inspect your roof on a dry, sunny day and look for raised bubbles or an uneven surface. From the inside, look for signs of poor ventilation or moisture like mold, musty smells, or ice dams in winter, as these can contribute to blistering.
While minor blistering might not immediately threaten your roof’s integrity, significant or spreading blisters should be checked by a professional roofer. A roofer can assess whether your shingles are still covered under the warranty, as some warranties won’t cover damage caused by blistering due to improper ventilation or installation. When calling a contractor, ask questions like: "What is causing the blistering in my shingles, and how can it be fixed?" and "Is my current attic ventilation adequate, or do you recommend improvements to prevent further damage?" These questions help ensure the roofer looks at the root cause, not just the symptoms. Avoid DIY fixes like applying roofing sealants or patching blisters, as improper methods can void manufacturer warranties and lead to bigger problems down the road. Instead, prioritize professional assessment to keep your roof healthy and protected.