What does hail damage look like on asphalt shingle roofs?
Areas of lost mineral granules will be apparent with more severe granule loss on roof slopes facing the direction from which the hailstones fell during the storm. When inspecting an asphalt shingle roof shortly after a hail storm if there has been roof damage, the shingles will show the areas of mineral granule loss have exposed "fresh" looking shingle substrate. The asphalt impregnated shingle substrate will not yet have been weathered by sun exposure.
Hail-Damaged Roof Shingles show more of a "scouring" effect in which larger and more irregularly-shaped areas of shingle surface have lost granules. Therefore, the damage has produced a shingle near the end of its product life than before the storm.
Wind Damaged Shingles are commonly the reason why you develop leaks through the ceiling and walls of your home. You may not even be aware you have a problem until the leak has already done considerable damage. Unless, you are in the habit of personally inspecting your roof for damage, a heavy wind can lift and crack your shingles where they are not visible from the ground.
When a contractor installs new asphalt shingles on your roof, he is careful to ensure the seals are intact. This helps to firmly attach one shingle to the next and prevent water from getting underneath. The shingles are then fastened to the roof with special roofing nails. A severe wind storm can compromise the roofs effectiveness.
A strong wind will grab the corner of a shingle and lift it up in the air tearing it away from the nails and/or separating the adhesive. Once the adhesive seal has been broken, it will not re-seal correctly and leaving the shingle vulnerable to rain and melting snow or ice. In many cases, the shingle is flipped up with enough force to fracture it just below the tabs causing it to break right off leaving an exposed section of the roof. Once the roofing seal is broken the roof is no longer water tight and cannot stop the water from accumulating below and finding a path into the interior structure of your home.
 
As your roof ages the wind damaged shingles become a greater risk. Aging asphalt shingles become more vulnerable due to weakening caused by granule loss. There are several additional factors that affect how well your shingles will endure high winds. This is based on the quality of the shingles,
roof pitch,
slope direction,and
amount of attic ventilation.
After a severe storm, it may be evident your shingles have been damaged by the wind because they are actually displaced and you find them lying on the ground. It is not as common to see shingles lifted which is hard to detect. Lifting is not visible from the ground in most cases.
Worn or Weathered Asphalt Roof Shingles are shingles that are losing their mineral granules in the course of normal aging. If shingles inspected early in the wear cycle start to show small areas of granule loss, beginning with bald areas on the shingles which may be just the diameter of a few mineral granules. As the sun and weather accelerate wear in these "bald" spots or micro-spots, an inspector will notice larger bald spots that have developed over time as opposed to having developed suddenly during a storm.
Confounding this is the distinction between hail damage as the main source of granule loss vs. the wear on an older asphalt shingle roof through normal wear. If the roof were worn (and its mineral granules less securely attached to the shingle surface), we would expect the roof will lose granules more quickly in the hail storm than a newer surface.
Inspect your roof as soon as possible after any storm.
Inspect your roof regularly, annually would be great, so that you can find and fix damage before it becomes a more costly leak. If you inspect the roof regularly you then can have information to compare with the condition of the roof after a severe storm - you can document when damage occurred and can establish that damage was or was not present before a particular storm.
Inspect your roof promptly after a storm: Any storm or wind alone can damage a roof, so the sooner you inspect the roof after a storm the better you can avoid leak damage inside the home, and if an insurance claim for roof damage is warranted, the better will be the data you can provide in support of your claim.
Inspect your roof gutters: before and after a storm. If the gutters were clean and after the storm they are loaded with mineral granules you have strong evidence of roof wear and damage due to the hail storm.
Hail damage versus asphalt shingle blister wear
Asphalt shingle blistering or rash blisters or other visual anomalies on a roof surface versus visual evidence of asphalt shingle hail damage can be tricky to distinguish. Some owners and some roof inspectors who have not seen various types of roof damage may have difficulty distinguishing between blistering, thermal splitting, age cracking, general product wear and granule loss, and other markings on asphalt roof shingles due to specifically hail, ice, or other storm damage.
Shingle rash blisters on asphalt shingles result from the manufacturing process, (and may be cosmetic or possibly a more serious defect) which are sometimes mistaken for hail damage.
Hailstones can be quite large, even golf-ball sized in some cases. Hail might produce a "dent" or a damage point in an asphalt shingle roof surface, resulting in granule loss and reduced remaining roof life. But I'm highly doubtful that hail ever produces raised "blisters" on the shingles such as shown in our description of shingle rash blistering.
Hail damage can dislodge the protective mineral granules of an asphalt shingle, producing areas of exposed asphalt shingle substrate. If inspecting an asphalt shingle (or mineral-granule-covered roof roofing) roof shortly after a hailstorm the exposed shingle substrate should be expected to show freshly-exposed asphalt coated or asphalt impregnated shingle base material. If the same area is examined much later the exposed shingle areas of granule loss may have weathered or even cracked and this distinction (hail versus wear or other sources of granule loss) will be more difficult to distinguish.
Asphalt shingle blisters, are raised bumps or protrusions in shingle surface, either closed blisters or open ones showing a small black pit or crater when the protective mineral granules have been lost from the peak of the blister.
Variations in shingle damage or wear according to roof slope pitch and weather or sun exposure.
Storm damage is likely to affect different roof slopes differently as their weather exposure varies.
It is possible for cracking to appear suddenly on asphalt shingles in response to cold weather, in the form of thermal splitting however, a failure for which we have a very different explanation and a differential cracking pattern.
Look at the uniformity of roof defects over the field of a given slope to help understand the probable cause. Blistering of asphalt shingles caused by the product itself might appear uniform over the roof on all slopes independent of weather exposure.
In other cases, if only a few bundles of shingles were defective, say from improper manufacture or storage, asphalt shingle blistering may appear in shingles in a specific pattern on a roof following the application pattern of the shingles themselves as they were nailed to the roof. Since roof shingles from a single bundle are usually applied over a single area of a roof, this pattern and cause may be self-evident on close inspection of the whole roof.
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