InspectAPedia ^®

Asphalt Roof Shingle Blistering vs. Storm or Hail Damage
InspectAPedia^®  -    

• How to identify hail damage on asphalt roof shingles
• How to distinguish asphalt roof shingle hail or other storm damage from other conditions
• Does hail damage shorten asphalt shingle roof life?

This website tells readers how to identify roof shingle hail damage and how to distinguish hail damage, storm damage from wind, and other conditions such as rash blistering, cracking, and granule loss associated with normal shingle aging.

By listing common causes of asphalt roof shingle failures and how to recognize them, building owners and roofing contractors may also be able to reduce the occurrence of asphalt roof shingle storage, handling, and installation errors that affect roof life. Readers are also invited contribute roof failure information to the web author for research purposes. web author for research purposes.

© Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use the links at page left to navigate this document or to go to Other Website Topics. Green links at left show where you are in our document & website.

Asphalt roof shingle hail storm damage versus blister rash on asphalt shingles

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 (or blew) during the storm. Inspecting an asphalt shingle roof shortly after a hail storm, if the roof has been damaged, should show that 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 damage to roofs versus shingle wear

Hail-damaged roof shingles we've seen or which have been sent along to us as in photo form, show more of a "scouring" effect in which larger, more irregularly-shaped areas of shingle surface have lost granules (and thus have produced a shingle nearer the end of its product life than before the storm.

Worn or weathered asphalt roof shingles which are losing their mineral granules in the course of normal aging, if inspected early in the wear cycle, already 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 wear will accelerate in these "bald" spots or micro-spots, when the inspector sees a larger bald spot it will be also weathered, having developed over time as opposed to having developed suddenly during a storm.

Confounding this distinction between hail damage and shingle wear as a source of granule loss, is the wear on an older asphalt shingle roof when exposed to a hailstorm. If the roof were worn (and its mineral granules less securely attached to the shingle surface), we posit that roof will lose more 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.

Look closely at the above photo of an asphalt shingle roof after a hailstorm. In the photo sent to me by a reader) we see cracks in some of the shingles. We would be surprised to learn that the impact of ice pellets on a roof would produce cracking and we pose that the cracks were a preexisting condition on an older shingle roof. (I have seen cracking 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 different cracking pattern than shown in the photo here--DF.)

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 all of 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.

Whose opinion on roof wear do you trust? Sources of conflicts of interest

While many roof inspectors and home inspectors are expected to be un-biased neutral professionals, we cannot assume that this is always the case. The building owner should consider possible sources of conflicting interests on the part of the person performing the inspection. These conflicting interests can occur in both expected and less obvious ways:

• Who is the roof inspector working for? Some roof inspectors working for the insurance company may be understandably motivated to focus on shingle wear rather than storm damage. If the insurance company inspector can give specifics of what s/he saw on the roof and what those clues mean (such as evidence of other signs of roof wear: cracks, blisters, tears) that opinion should be considered seriously.
• Will the roof inspector gain financially by the inspection outcome? if the roof inspector is asked to advise on whether or not the roof needs immediate replacement, and if s/he works for a roofing company, the "safe" as well as "profitable" opinion to offer is that replacement is needed.
• Experienced roofing contractors who conclude that the roof does not need immediate replacement but who have seen many roofs in a given geographic area in many conditions, who give specific details of what s/he saw and what those clues mean, and who conclude that the damage is due to hail (or another cause), have offered an opinion that should be taken seriously.

In sum, ask the roof inspector for specific details that support his or her conclusions about the condition of the roof and about what caused its damage or wear. An inspector who offers only the "bottom line conclusion" with no supporting evidence, does not deserve the confidence of the building owner.

Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website. If you just "scroll down" you'll miss some important articles. See links at page left.

Share this Article      

...

Technical Reviewers & References

Search InspectAPedia

• Daniel Friedman - principal author/editor of the InspectAPedia^® Website
• InspectAPedia Bookstore lists recommended books, organized by topic & available for purchase. Most of our articles also include a list of recommended books for the specific article topic as well as other references, and information sources.
• Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
• Additional technical contributors & reference sources for this article are listed below.

Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website. If you just "scroll down" you'll miss some important articles. See links at page left.

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

More Information on Building Diagnostic Inspections and Repairs

...

InspectAPedia® Home & Site Map - Building & Environmental Inspection, Testing, Diagnosis, Repair, & Problem Prevention Advice: In-depth research & advice on diagnosing, testing, correcting, & preventing building defects & indoor environmental hazards. Unbiased information, no conflicts of interest.

The Mold Information Center: What to Do About Mold in Buildings, When and How to Inspect for Mold, Clean Up Mold, or Avoid Mold Problems

Use this simple, economical mold test kit by following our instructions on how to collect and mail mold samples to our lab

Environmental Inspection, Testing, & Diagnosis On-Site IAQ, Gas, Air Testing, Mold Investigation, Sick Building Diagnosis, Lab Services, & Remediation Plan Preparation - indoor air quality testing, problem source determination, supporting lab work, written remediation plan addressing removal of environmental and other hazards and prevention of their recurrence.

Building Inspection, Problem Diagnosis, Forensic Investigation & Testing, Repair Consulting

Contact Daniel Friedman for website content suggestions or for fee-paid consulting