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Bald, worn-out organic asphalt roof shinglesLoss of Roof Shingle Mineral Granules as a Sign of Roof Wear
8 Causes of Asphalt Shingle Granule Loss on Roofs

  • GRANULE LOSS from SHINGLES - CONTENTS: Causes & effects of loss of protective mineral granules from roof shingles. Description of different causes of roof shingle granule loss: normal, defective product, storm damage, foot traffic, etc. How to Inspect a Roof for Loss of its Protective Coating of Mineral Granules. When does granule loss mean that a new roof is needed?
  • POST a QUESTION or READ FAQs about the cause and significance of lost mineral granules from asphalt shingle & roll roofing surfaces
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Loss of mineral granules from asphalt shingle or roll roofing roofs:

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.



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Mineral granule loss from asphalt roof shingles

Photograph of Photograph of roof shingle mineral granules in the gutter due to hail damage

[Click to enlarge any image]

This roof gutter sports about an inch of mineral granules that have washed off of the asphalt-shingle roof. Is that a problem? We'll see.

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.

Eight 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.

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

  1. ROOF GRANULE LOSS, NEW - Asphalt shingle mineral granule loss on a new asphalt shingle roof
  2. ROOF GRANULE LOSS, BLISTER RASH - Asphalt shingle mineral granule loss due to roof shingle blistering
  3. ROOF GRANULE LOSS, OLD ROOF - Asphalt shingle mineral granule loss on old, worn-out asphalt shingle roofs
  4. ROOF GRANULE LOSS, WALKING-ON - Asphalt shingle mineral granule loss from being walked-on or mechanical damage
  5. ROOF GRANULE LOSS, HAIL DAMAGE - Asphalt shingle mineral granule loss due to hail or other storms
  6. ROOF GRANULE LOSS, NORMAL - Asphalt shingle mineral granule loss on an asphalt shingle roof due to normal aging
  7. ROOF GRANULE LOSS, DEFECTIVE PRODUCT - Asphalt shingle mineral granule loss due to defective roofing product
  8. ROOF GRANULE LOSS, IMPROPER STORAGE - Asphalt shingle mineral granule loss due to damage shingles from improper storage

This article also describes:
ROOF GRANULE LOSS INSPECTION PROCEDURES
and we also discuss
ROOF GRANULE LOSS & RE-ROOF DECISION

Normal Mineral Granule Loss on a New Asphalt Shingle Roof

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.

Shingle granules visible at downspout end (C) Daniel Friedman

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.


Normal but worn out roof (C) Daniel Friedman

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.

Normal shingle granule loss means that there has been no single event that has damaged the roof, that the quantity of granules lost from or remaining on the shingles is typical for the chronological age of the roof, and that thus the "wear age" of the roof (it's remaining life compared with its original warranty or projected roof life) is about the same as the roof's chronological age, after we factor
in ASPHALT SHINGLE LIFE / WEAR FACTORS.

Details and photos of normal roof granule loss are at Roof Granule Loss Due to Normal Aging in this article (below).

Roof Shingle Granule Loss from Damaged Shingle Blisters

Asphalt shingle blisters on Atlas Chalet shingles 4 years old (C) Daniel Friedman Jim todd<

Granule loss due to blistering: blisters or "pimple-like" protrusions from a shingle surface may be a "cosmetic" manufacturing defect (at least in the opinion of the manufacturers).

On at least some roofs we find that these blisters ultimately become the first wear points on the shingle when their upper surface wears away (perhaps from foot traffic or weather) exposing small round dots of missing granules on the shingle.

Watch out: walking on a badly-blistered roof may cause damage visible as granule loss or pits.
See ROOF INSPECTION SAFETY & LIMITS

We discuss this defect and how to distinguish between defective shingle product and storm damage
at ASPHALT SHINGLE BLISTERS

Roof Shingle Granule Loss on Old, End-of-Life Roofs

Bald, worn-out organic asphalt roof shingles

Granule loss on old asphalt shingle roofs: when an asphalt shingle roof is nearing the end of its life we may see that granules have begun to wash off of the shingles so as to leave large "bald" or nearly bald areas showing black shingle substrate.

These shingles have more porosity than those where their mineral granules remain in place and may already be leaking even if leaks are not quite visible in the building interior. Such a roof is ready for replacement.

Roof Shingle Damage from Mechanical Forces: Walking-on, Chopping

Cracked broken roof shingles (C) Daniel Friedman

Granule loss on a roof being walked-on: walking on any asphalt shingle roof loosens some of the mineral granules from their attachment embedded in the asphalt used to impregnate and coat the shingle. If there is a lot of roof traffic, such as when work is being done on a chimney, you may see "bald" areas of shingles with lost granules where people have been walking.

The (older, more brittle) roof at left suffered both granule loss and cracked shingle corners after it was walked-on.
See ROOF INSPECTION SAFETY & LIMITS

This is damage caused by workers and is not a product defect. Some examples and photos of shingle damage that occurred at least in part due to foot traffic on a roof, and that produced lots of granule loss from the surface can be seen at MECHANICAL DAMAGE of SHINGLES.

At an arbitration hearing involving a roof dispute we could actually track the footprints (and damage) across an older roof that had been walked-on (and damaged) by the very contractor who told the owner she needed a new roof. (Don't walk on fragile roof surfaces).

Roof Shingle Granule Loss from Hail Damage

Hail damaged shingle - scouring (C) Daniel Friedman

Granule loss on asphalt shingles due to storms, especially hail: it is possible that severe weather, such as hailstorms, may damage shingles producing pitting and granule loss.

Such roofs have a reduced remaining life, depending on the severity of damage.

See HAIL DAMAGED SHINGLES for more detail on this source of asphalt shingle roof damage and for more photographs of asphalt shingles that have been deprived of their protective coating of mineral granules.

Roof Granule Loss Due to Normal Aging

Granule loss due to normal wear and shingle aging

The organic felt-based asphalt shingles shown at below left has lost some granules into the roof gutter but an inspection of the shingles themselves showed no significant bald areas. We had to look closely at those shingles in the upper right of the photo and we decided the wear was probably due to foot traffic as well.

The organic-mat asphalt roof shingle shown at right, also showing normal wear, is completely worn out, showing shingle substrate, sun and heat damage, and basically, that the roof needs to be replaced. A shingle like the one shown is usually so fragile that stepping on it breaks it into many small fragments.

Photograph of roof shingle mineral granules in the gutter (C) Daniel Friedman

These shingles (above right) may already be leaking into the roof substrate, placing water between the shingle and its felt underlayment, between the underlayment and the roof sheathing, or leaks may be entering the roof structure. Even if there is no visible evidence of leaks in the living area (such as stains on top floor ceilings or visible water in the attic) this roof is at the end of its life.

Worn out roof shingle (C) Daniel Friedman

Wherever and whenever a roof shingle has lost the protection of its mineral granules that shingle has a reduced life expectancy. In all climates the loss of granules means that area of the roof shingle has lost its protection from sunlight. In freezing climates, shingle wear may accelerate in the area of lost granules as the roof ages and is exposed to freeze thaw cycles.

Mineral Granule Loss Due to Defective Roofing Product

Roof shingle granule loss due to defective roofing product usually exposes the shingle substrate in "premature bald" patches and is identified by bald spots or exposed shingle substrate on roofs early in their chronological life, often distributed uniformly over the roof or in areas of the roof where shingles from a particular pallet of roof shingles were installed.

Below (left), the picture of bald areas in this laminated asphalt shingle or "architectural shingle" roof show white fiberglass roof shingle substrate. Our OPINION was that this was a defective roof product. This same roof also suffered thermal splitting or tearing damage (below right). Photos of roof damage below were provided by ASHI Home inspector Steve Mauer and photographed in 2009.

Our OPINION is that the asphalt roof shingle granule loss shown at below left is due to a defective product.

Thermal cracking laminated asphalt shingle (C) D Friedman S Mauer

The shingle tearing and splitting shown below on the same roof is also often a product defect referred to as thermal splitting.
See CRACKS in FIBERGLASS SHINGLES for an explanation of splits or cracks in asphalt shingles.

Thermal cracking laminated asphalt shingle (C) D Friedman S Mauer

Asphalt Shingle Mineral Granule Loss due to Improper Shingle Storage

Asphalt shingle granule loss in specific shingle bundles (C) Daniel Friedman

The roof shown above was observed on a home in Haddonfield, New Jersey in the U.S. That the shingles were installed in a ladder pattern has become obvious as sections of these roof shingles have lost more granules than their neighbors. The loss of the tan colored mineral granules is leaving the black asphalt shingle substrate exposed. Laddering or stair-step installation of shingles is not the best roofing practice and it, too, can contribute to other roof wear or leak problems that we don't see on this roof, but laddering is permitted by roofing installation practice guides.
See LADDERING vs STAIR STEPPING SHINGLES.

However because shingles installed in a ladder pattern tend to be grouped in batches of shingles were set on the roof for installation from individual shingle bundles, often the loss of mineral granules not only tell us the shingle installation pattern but also they tell us something about variation in shingle durability or variation in shingle granule loss in individual bundles of shingles that otherwise were (probably) manufactured in the same production run.

This distinction is significant. If all of the shingles on a roof were produced in the same manufacturing run but if we then see that groups of shingles wear differently even though installed on the same roof slope, exposed thus to the same sun and weather conditions, we can infer that there were variations in condition among the individual bundles of shingles. Typically three bundles of shingles make up one square (100 sq .ft.) of roof covering.

A common explanation of this variation in shingle durability by bundle is improper shingle storage such as leaving a pallet of roof shingles exposed to weather for some time before they are used. Shingles on the top of the pallet become rain-soaked and may suffer damage.
See ROOF SHINGLE STORAGE.

How to Inspect a Roof for Loss of its Protective Coating of Mineral Granules

Check the shingle surface for mineral granule loss

The critical place to evaluate the condition of roof shingles is at the edge of or (if safe and the roof is not fragile), on the roof itself. Look closely at those shingles - get down on your hands and knees and look closely for early wear signs such as tiny bald spots, pits, cracks, or other damage. If you can't see obvious bald areas from which the protective granules have been lost from the shingle, it's unlikely that granule loss is a current problem.

Look in the gutters for lost mineral granules from the roof

Photograph of roof shingle mineral granules in the gutter

The photograph at above left shows a modest amount of mineral granule wash-off into the gutter of this home. If the roof is a new one, this may be a normal amount of granule loss. When the gutter is cleaned out completely, you should not see this same level of mineral granules again soon. If you do, there may be a rapid wear problem going on with the roof, or someone may be dancing on it.

Photograph of Photograph of roof shingle mineral granules in the gutter due to hail damage

The photograph at above right shows a significant loss of mineral granules into the gutter on this roof. A look at the scoured surface of the roof shingles and a report by the owner of a recent and significant hail storm suggest that this granule loss may have been due to hail damage. we discuss evaluating hail damage to roofs and how to distinguish hail damage from other sources of shingle granule loss at HAIL DAMAGED SHINGLES.

Look on the ground for lost mineral granules from the roof

Check the ground surface at the end of the downspouts or roof leaders. If you see lots of mineral granules there the roof is either brand new or badly worn. A check of the roof surface easily distinguishes between these two conditions.

Translating Asphalt Shingle Damage or Wear into the Decision to Re-Roof

Extensive shingle granule loss alone, sufficient to expose the roof shingle substrate, means that the wear rate on the roof will accelerate. That's because the shingle body is exposed to direct sun and in freezing climates because the exposed shingle substrate begins to absorb water, suffering from the freeze-thaw cycle. In other words, once the shingle substrate is exposed by mineral granule loss, that area of the shingle will absorb more water than its neighbors.

When shingle granule loss is extensive or when it is combined with other roof defects (such as tears, cracks, brittle shingles that can't be walked-on for patching, or more than just a very few readily-accessible (patchable) defects, those will usually form a sound basis for asserting that the roof is already leaking (at those cracks) even if water has not appeared on finished ceilings inside the home, and they both argue that this roof has no predictable useful remaining life.

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Continue reading at HAIL DAMAGED SHINGLESor select a topic from closely-related articles below, or see our complete INDEX to RELATED ARTICLES.

Or see ASPHALT SHINGLE FAILURE TYPES

Or see ASPHALT SHINGLE LIFE / WEAR FACTORS

Or see ASPHALT ROOF SHINGLES - home, for all articles about asphalt roof shingles

Or see ROOFING MATERIALS TEST LABS

Or see WARRANTIES for ROOF SHINGLES

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GRANULE LOSS from SHINGLES at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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