What Causes Asphalt Shingle Blisters?

Blisters developing on asphalt shingles is not as common as it used to be, but it can happen from time to time. But what causes roof blisters, and what can you do about them?

How Are Asphalt Shingles Made?

Before we take a look at what causes asphalt shingle blisters, let us first take a detour, and look at how asphalt shingles are made. Asphalt shingles begin their life as large spools of backing material, which are loaded on a series of equally large rollers. Most of today’s asphalt shingles feature backing material made of fiberglass (also known as composition shingles), though traditional ones made of paper and fabric pulp (“organic” shingles) are still being made.

The sheets of backing material pass through poured hot asphalt several times, soaking them. A layer of granules are then pressed on one side of the backing material while the asphalt is still hot, becoming embedded as it cools down. The granules protect the asphalt from damage caused by ultraviolet (UV) radiation. It also provides the colors and other features like algae resistance. The cooled sheets are then dusted to prevent sticking, cut to size (in case of architectural shingles, two layers are laminated) and packed, ready to be installed.

What Causes Blisters on Asphalt Shingles?

Blisters are formed when moisture trapped between the asphalt and granule layers expand and contract when heated by the sun. When asphalt shingles pop and dry out, they leave small craters that are often mistaken for hailstone damage. Reputable roofing manufacturers help prevent asphalt shingle blisters by carefully monitoring humidity levels during the manufacturing process.

Can Asphalt Shingles Be Fixed?

Fixing asphalt shingle blisters involve replacing the defective shingles. Most roofing warranties include coverage for replacement asphalt shingle blisters as it’s considered a manufacturing error. It’s important to note that labor costs may or may not be covered depending on your level of warranty coverage.

Krech Exteriors is the leading provider of roofing services to customers in Minneapolis and St. Paul. Give us a call at (651) 688-6368. You can also fill out our contact form to schedule an appointment.