Looks like hail damage, but not quite! What is this?
Ah yes, Blistering!

What is Blistering?

Blisters appear when there is trapped moisture or air beneath the layers of roofing or within the shingles themselves. As the temperature outdoors continues to rise, the pressure in these patches forces the air or moisture to expand. The asphalt will begin to weaken as a result, forming a blister on the surface of your roofing material.

In most cases, blisters are small and harmless. However, there are times when these blisters allow higher levels of moisture of rainwater to seep below the surface, causing more and severe blisters. Sooner or later, your roof will develop leaks, compelling you to call for a roof replacement.

Blisters often occur when excessive heat damages the roofing materials. When you have no shade to block direct sunlight to a roof, small blisters can form. Obviously, with the excessive heat we have here in Texas, this is a very common occurrence.

What Causes Blistering?

According to the International Association of Certified Home Inspectors (InterNACHI), poor ventilation is the primary cause of roof blisters. However other causes can include:
  • Trapped moisture combined with excessive heat.
  • Poor quality shingles
  • Poor Installation

How Can I Prevent Blistering?

The best thing you can always do to prevent blistering is to choose high quality asphalt shingles when constructing a new roof. Making a good choice will go a long way in preventing blisters since good shingles may be durable enough to avoid blister popping at least. Provided the vapor contracts or the moisture evaporates, the blisters should just go away without resulting in any real damage to the roof.
However, if you do find yourself with these types of spots on your roof it is absolutely best to call a reputable roofing company out to provide an inspection. Blisters that are larger in size can cause damage including leaks, and allow water to seep in to your interior, and overtime compromise the integrity of your roof system.
A reputable roofing company can help you document the damage, define the cause of the blistering and even help you to make the right installation and product choices to prevent these types of issues in the future, whether that be ensuring proper attic ventilation or high quality product selection to act as a prevention method.
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