Causes & effects of the loss of protective mineral granules from asphalt roof shingles or roll

Causes & effects of the loss of protective mineral granules from asphalt roof shingles or roll

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This roof leak article explains the causes & effects of loss of protective mineral granules from roof shingles. Shingle granule loss defects occur on organic-mat or fiberglass-mat asphalt roof shingles and, depending on the cause and extent of mineral granule loss, the loosening of this protective coating can spell the end of life of an asphalt shingle roof or the demise of a mineral-granule-coated roll roofing roof.

Mineral granule loss from asphalt roof shingles

Roof shingle granule loss may be normal shingle wear, hail damage wear, or defective roofing product, as we explain here. The page-top photograph shows severe loss of mineral granules from an asphalt shingle roof. This "bald" asphalt shingle roof is way past needing replacement and is almost certainly leaking. Even a roof with less dramatic granule loss is showing signs of wear and reduced future life. Readers are also invited contribute roof failure information to the web author for research purposes. web author for research purposes.

The job of these mineral granules which are adhered to the roof shingle surface as part of the shingle manufacturing process, is to protect the shingle from sunlight, from UV light, and from the weather in general.

The selection of roof shingle color is also determined by the choice of its coating of mineral granule; lighter colored shingles may remain a bit cooler and at least in some applications (hot sunny climates) may have a longer life than dark-colored shingles.

Types of Mineral Granule Loss on Asphalt Roofing Shingles

While in our page top photo the roof is "worn out", there are quite a few other conditions that can produce mineral loss on asphalt shingle roofs. Diagnosing the correct cause of granule loss is useful in helping to assess the probable remaining roof life and it may play a role in roof shingle warranty claims or insurance claims related to storm or hail damage.

Below we define, contrast, and illustrate all types of mineral granule losses that occur on asphalt roofing:

Causes & effects of the loss of protective mineral granules from asphalt roof shingles or roll
  • Mineral granule loss on a new asphalt shingle roof
  • Mineral granule loss on an asphalt shingle roof due to normal aging
  • Mineral granule loss due to roof shingle blistering
  • Mineral granule loss on old, worn-out asphalt shingle roofs
  • Mineral granule loss from being walked-on or mechanical damage
  • Mineral granule loss due to hail or other storms
  • Mineral granule loss due to defective roofing product

Granule loss on a new asphalt roof. loose mineral granules wash down the roof and will appear in gutters and at the ends of downspouts. You can begin this roof condition assessment at the ground, before even looking at the roof itself.

If the roof is reported to be new, the granules shown in our photo are normal and not a worry. [Or they could be there having washed off of an older worn out roof that was just replaced.] Especially right after an asphalt roof has been installed, granules that were loosened on it surface from walking by the installers will wash down and off of the roof surface. Provided the roofers were careful not to dance the Twist while roofing on a hot day, the roof should be fine.

But if the granules appear after a hail storm, or if the roof is quite old, they are more likely to indicate roof wear and/or damage.

Just take a close look at the shingles themselves for granule loss. And if you clean out the gutters you’ll find it easy to see if this granule loss is continuing. Look in the roof gutters for shingle granules too.

Roof granule loss due to normal aging occurs over the life of an asphalt shingle roof as weather and sun exposure cause the roof shingle to lose its flexibility, as the roof is exposed to changing temperatures, etc.

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