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Loss of Roof Shingle Mineral Granules as a Sign of Roof Wear
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• Causes & effects of loss of protective mineral granules from roof shingles
• Types & photographs of asphalt roof shingle defects & failures

This website explains the causes & effects of loss of protective mineral granules from roof shingles. These 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.

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.

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Mineral granule loss from asphalt roof shingles

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. Granule loss due to normal wear and shingle aging: These organic felt-based asphalt shingles are also worn and are at about the end of their useful life. The granule loss is not as severe as the page top photograph, but the shingle has become porous (and also cracked) where granules have washed off and the material has aged. These shingles 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 or near the end of its life. 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. Once the shingle substrate is exposed by mineral granule loss, that area of the shingle will absorb more water than its neighbors. While in this photo the roof is "worn out", there are several other conditions that can produce mineral loss on asphalt shingle roofs. We list them just below. 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. This is a normal condition unless it continues and begins to show black exposed roof shingle substrate. 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. 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. 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. 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. 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. We discuss this defect and how to distinguish between defective shingle product and storm damage at ASPHALT SHINGLE BLISTERS,

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

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.

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.

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ASPHALT ROOF SHINGLES
  SHINGLE LIFE / WEAR FACTORS
  ASPHALT SHINGLE FAILURE TYPES
  ALGAE, FUNGUS, LICHENS, MOSS on SHINGLES
  BLACK STAIN REMOVAL & PREVENTION
  BLISTERS on ASPHALT SHINGLES
  CRACKS in FIBERGLASS SHINGLES
  CUPPING ASPHALT SHINGLES
  CURLING ASPHALT SHINGLES
  FISHMOUTHING ASPHALT SHINGLES
  GRANULE LOSS from SHINGLES
  HAIL DAMAGED SHINGLES
  LADDERING & STAIR STEPPING SHINGLES
  MOSS & LICHENS on SHINGLES
  ORGANIC FELT SHINGLE DEFECTS
  SPLICE DEFECTS on ASPHALT SHINGLES
  STAINS on ROOF SHINGLES
  WHAT ARE ASPHALT SHINGLES

• Mark Cramer Inspection Services Mark Cramer, Tampa Florida, Mr. Cramer is a past president of ASHI, the American Society of Home Inspectors and is a Florida home inspector and home inspection educator. (727) 595-4211 mark@BestTampaInspector.com
• Hankey and Brown home inspectors, Eden Prairie, MN, technical review by Roger Hankey, prior chairman, Standards Committee, American Society of Home Inspectors - ASHI. 952 829-0044 - hankeyandbrown.com
• Arlene Puentes, a licensed home inspector, educator, and building failures researcher in Kingston, NY

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