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 Asphalt Roof Shingle Storm or Hail Damage vs Shingle Blister Damage
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InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
Hail damage to asphalt roofing: This article tells readers how to identify
roof shingle hail damage and how to distinguish a hail damaged roof from blister rash damage, foot traffic damage, wind,
and other conditions such as shingle rash blistering, cracking, and granule loss associated with normal shingle aging. We include photographs and text that help identify different types of roof damage and wear, and we discuss up-close examination of wear areas to improve the accuracy of roof damage or wear diagnosis. We explain the role of hailstone size, direction, and velocity in roof damage from hailstorms, and we discuss the role of roof slope or pitch, orientation and other factors in roof wear. We also include a set of codes that can be used in marking areas of wear or damage on roofs to assist in photo documentation of roof condition. The article includes a list of manufacturers of hail-damage resistant roofing products and invites questions or comments from building owners, roofing experts, insurance company adjusters and roofing manufacturers.
Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
How to Distinguish Wear Types on Asphalt Shingle Roofs: hail storm damage vs. blister rash vs. foot traffic wear on asphalt shingles
 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.
Also see BLISTERS on ASPHALT SHINGLES and GRANULE LOSS from SHINGLES and CRACKS in FIBERGLASS SHINGLES.
Notice to insurance adjusters, building owners, roofing contractors:
We invite questions, comments, polite debate, and importantly, sharp photographs of damaged and un-damaged roof shingles to permit us to develop a free public reference library of roof conditions, damage types, and thus to assist in damage assessment.
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.
What does hail damage look like on asphalt shingle roofs?
Start by looking in your roof gutters and on the ground for large amounts of mineral granules lost from the roof. And if you are on-site during the hail storm, record the storm details: storm duration, hail size, wind direction, if you can. The photos below of mineral granules in a previously clean roof gutter, and of actual hailstones were provided by reader L.B. whose roof damage case is discussed below.
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 normal or typical asphalt 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.
Also see LIFE / WEAR FACTORS in SHINGLES and MECHANICAL DAMAGE of SHINGLES.
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.
Role in Roof Damage of Hailstone Size, Mass, Terminal Velocity, Wind Direction, and Roof Slope
The impact of hailstones on a roof depends on at least these factors:
- Size: The size of the hailstone
- Mass: Some assumptions about the typical mass of a hailstone (ice or ice with some water coating)
- Wind: The effect of wind on the object's velocity
- Falling height or distance (we assume the distance is sufficient to reach terminal velocity before considering wind effects)
- Mechanics: The assumption that all of the physical energy is converted to kinetic energy as the object strikes the roof
- The pre-existing condition of the roof surfaces, age, existing damage or wear, fragility
- The roof slope and angle of presentation of the roof slope to the direction of wind-driven hailstones
The hailstones in your photo look as if they averaged roughly 1 cm or larger (you reported 0.88 inches or 2.2 cm).
A 1 cm hailstone has a theoretical terminal velocity of about 20 mph (9 meters/second). Larger hailstones have a much higher terminal velocity. And a ten-gram hailstone falling from 10 km (this distance is probably more than enough) has a terminal velocity of about 15 meters per second. [1]
What the experts cite as hailstone terminal velocity is, in my opinion, misleading because that figure does not consider the role of winds that typically occur in a storm, nor the relationship between the angle of the roof and the angle of movement of the hailstone. For example, wind-driven hail may be accelerated beyond simple terminal velocity (gravity).
In LB's "old shingle" shingle photos taken on the roof itself, most of the open pits or craters on shingles where mineral granules have been lost appear to be in relatively flat areas shingles. Mineral granules that have been lost to expose shingle substrate in the center of raised blisters will in at least some instances leave a crater around the pit edges.
Examination of the shingle pits or craters in a stereo microscope such as we use in our lab would be helpful in making this examination.
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 [BLISTERS on ASPHALT SHINGLES] 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. - [Photo above /left courtesy of reader Jim Todd.]
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 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.
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Photos of Asphalt Shingle Blisters Converting to Pitting
Asphalt roof shingle manufacturers emphasize that blisters on shingles are simply a cosmetic matter and that they do not impact the wear life of the roof nor do they impact the roof shingle warranty.
See BLISTERS on ASPHALT SHINGLES and our shingle blister photo at left.
We are not sure that everyone would agrees about the impact of blistering on shingle life nor the view that blistering cannot ever affect the roof life.
While on some roofs blistered shingles may last at least as long as the shingle warranty period., in other cases, especially if the blistered roof is exposed to mechanical damage (being walked-on, for example) or other challenging exposure conditions, the blisters may play a role in roof wear and roof life, as we elaborate below. |
In at least some cases, blistered asphalt shingles are more easily converted to pitted shingles by foot traffic, hail, and in some cases during the course of aging but before the end of the shingle warranty period.
Our photo (left) shows blisters on an Atlas brand asphalt shingle roof in Georgia. Some, circled in red [click to enlarge] show remaining blisters that are either not opened to its or are just beginning to open.
The blister-damaged Atlas brand roof shingle shown at left is not the hail-damaged Owens Corning brand asphalt shingle roof described by reader B.L. in this article.
In those cases, in our OPINION and also our EXPERIENCE, because mineral granules have been lost from the shingle surface sufficient to expose the shingle asphalt-impregnated substrate to the sun and weather, the shingle wear rate may accelerate and the shingle life may be reduced.
CONTACT us to suggest technical corrections, additions, or references on hail damage and blister damage to roofing.
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Question: How Can You Distinguish Between Blister Damage and Hail Damage on an Asphalt Shingle Roof?
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I notice your website attributes blistering most frequently to organic (rag based) asphalt shingles. So, I have a question for you:
My roof [on a Pennsylvania home] has 13 year old Owens Corning three tab 25 year warranty Supreme fiberglass shingles. After a severe hail storm on 29 March 2009, with wind gusts of 60+mph and .88" diameter hail, my roof sustained severe damage to the southern roof slopes.
The southern slopes were perpendicular to the incoming hail. After the storm, I had over 1/2" of granules in a brand new gutter and the southern slopes were strewn with thousands of 1/8" to 3/16" pits. The underside of the shingles did not show any cracking or indentations (as would be expected from .88" diameter hail).
I was on my roof 5 months prior to the storm and replaced 3 pipe boots on the southern roof slopes. The shingles NEVER exhibited any raised bubbles; they were always smooth and flat. My weight did not disturb anything more than a few stones from the roof surface. Prior to the storm, there was nothing on my roof that looked like the attached photo. (Please see the photo [above left, sharpened by InspectAPedia.com] - sorry it is a little blurry).
An inspector from the insurance company is saying my 13 year old roof is blistered. He showed me a photo of burst blisters, which I have to admit, looked like my damage. All the research I can find (by the way your web-site is awesome!), indicates that 13 year old fiberglass shingles don't suddenly develop a manufacturing or installation issue known as blistering. I say this is hail damage!
My question is this: have you ever seen this scenario before and can you draw any conclusions from my information?
- B.L., Pennsylvania
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Reply: Blisters on Asphalt Shingles,Should Be Visible In and Out of the Hail Damage Area & on All Slopes Regardless of Roof Orientation & Direction of Hailstones if They Are or Were Present Before the Storm
A competent onsite inspection by an expert usually finds additional clues that help accurately diagnose a problem. That said, here are some things to consider:
Here is my reasoning on the question of distinguishing among simple hail damage, hail damage to a blistered roof, and shingle blister wear on a roof:
- Your photo of roof damage [at the start of this Q&A] after the hail storm is blurry but it clearly shows pitting on the shingles on this home in Pennsylvania. Your second photo (shown at left, click to enlarge) shows what may be a pre-existing blister - circled - whose top has been opened.
You will want to survey the roof surface carefully, perhaps in early morning or late afternoon angled sunlight or even at dusk with a flashlight shone along the surface, in order to see what other roof blisters may be present in various areas of the roof and thus to decide what role pre-existing blisters, even if they were not previously open or "burst" may have played in the hail damage.
- We are not sure that hail will necessarily produce cracks or dents shown on the underside of asphalt roof shingles. That material, if the roof shingles are not old, dried and brittle, is resilient to impact. Cracks in my experience come with age, loss of volatiles, and shingles becoming dried and brittle. Or in some cases cracks occur from defective product.
- The presence of mineral granules in quantity appearing after a hailstorm and in the previously new clean gutters is a strong indication that the roof suffered granule loss during the storm. A question is where there previous blisters on the shingles and did that play a role in the granule loss and does that affect the shingle warranty or an insurance claim for hail damage following a hail storm.
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- A common form of hail damage to asphalt roofing is a shingle scouring effect shown in our photo (left). But if a roof were blistered before the storm those raised areas might play a role in granule loss from hail impact.
- We agree with the insurance company investigator that shingle blisters (see BLISTERS on ASPHALT SHINGLES) can deteriorate to shingle pitting, and often will ultimately do so from foot traffic or just shingle aging depending on how long the shingles remain on the roof.
- Blisters on asphalt shingles can also convert to pitting due to hail damage, and in that case one might argue that the roof age or wear was accelerated by the hail storm that burst the blisters leaving the pits.
- But if blisters were the source of pitting on your roof, one would expect to find some remaining, un-burst blisters, perhaps lower in profile. It seems to me less likely that even on a blistered roof we would get 100% blister bursting in a hailstorm. So a careful inspection should find some remaining blisters, or at a minimum, raised edges (previously blister edges) around the pits on the shingles now, after the storm.
- If there are NO blisters on the roof shingles now, and considering that you report not having seen blisters before the storm, and since post hail we see just pits (no unopened blisters), and particularly if the pitting occurs on the slopes most impacted by the hail, hail damage sounds like a likely explanation.
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Home "Oven Test" Attempts to Replicate Roof Shingle Damage from Hail
B.L. continues our hail damage and roof blister discussion with a do-it-yourself home test of roof shingles and more photographs of shingle granule loss.
Are you saying that the photos look like blistering?
I did some testing over the weekend. I took brand new shingles and some from my unaffected front roof. I mounted them to a piece of roof sheathing, added felt paper, and overlapped the shingles as they would be installed in the field.
I then tried to simulate the weather they were exposed to before the hailstorm. First I put the assemblies in the oven and heated them to 100F (checked with a calibrated laser sensor) to simulate the roof temperature with an outdoor ambient air temperature of 70F. |
[Photo below left: closeup of shingle condition on the roof following a hail storm. Photo below right, closeup of shingle mineral granule loss after B.L.'s home oven test.]
Watch out: readers should keep in mind that cooking potentially combustible materials in a home oven is a potential fire hazard.
I next set the assemblies outside for 45 minutes in the 50F air temperature to simulate the temperature drop before the hailstorm. The temperature of the shingles dropped to around 65F. I next sprayed the assemblies with cold water from the hose to simulate the ice cold rain. The shingle temperatures dropped to around 45F. I next threw 1" diameter ice cubes at the assemblies and then washed them down with another spray of water from the hose.
Interestingly, the ice impacts did not imbed granules into the asphalt. Some granules broke away from the surface of the shingles taking the asphalt with them. These small spots revealed the fiberglass mat. My assumption is that the coldness of the rain and ambient air temperature made the asphalt hard and brittle versus soft and pliable. When the hail hit the roof it separated the hard asphalt from the fiberglass. Then the stones just washed away with the asphalt still intact.
I have attached photographs of the test results [see above]. I think the damage looks the same on both old and new shingles (but it is more severe on the old shingles that were about half way through their service life). Unfortunately I could not simulate hundreds of hits in the same area for about a half an hour.
My test had very few impacts because it was limited to the amount of ice I had available. I think if I could have hit some of the same areas that lost the stones already, I think I would have been able to replicate the hail damage sustained to my roof on March 29, 2009.
Your thoughts?
Reply: The Account Supports Hail Damage, But Asphalt Shingle Blisters, Even Hard-to-See Blisters may Increase Shingle Hail Damage Vulnerability
 No, I'm not saying that the primary cause of your roof shingle granule loss is due to blistering alone. Your account of the before and after roof inspection and description of the damage (no visible granule loss before storm, lots of granules lost after storm) very strongly supports your claim of hail damage.
Here we are discussing the role that pre-existing and not easily-visible roof blisters might play in hail damage on a roof.
However I reported that one of your photos shows what appears to be slight blistering and one or more blisters that have only slight opening or top punctures.
Therefore I pose that there may be some blisters on shingles that were not obvious to you - you can check best using oblique lighting as I said earlier.
Nevertheless, your account points to hail damage. The relationship of hail damage to blisters is, in my opinion, derived from the premise that if an asphalt roof has shingle blistering, just as I've said elsewhere that foot traffic can damage those areas, so might hail damage cause additional damage by puncturing and opening the tops of blisters earlier than would have otherwise happened due to normal aging.
The theory of relationship between preexisting blisters on a roof (possibly not showing as open craters or pits) and hail damage is based on an important observation: that the raised "bumps" are true blisters - that is that they are true raised blisters, with some hollow core and a top blister shell (to be burst by foot traffic, hail, or other mechanical damage). In contrast, apparent blistering or blister rash on shingles is comprised of similar looking bumps, but each raised area is comprised of solid material (asphalt and mineral granules, for example), those bumps may be less vulnerable to converting to open craters or pits due to mechanical wear.
About the Do-it-Yourself Roof Shingle Test for Hail Damage
I am not sure that a professional shingle test lab would necessarily like your home oven test, as there are ASTM and other roof shingle testing standards, but I agree that your photographs of your oven-tested roof shingles and the on-roof shingle damage look similar.
Certainly your home test was likely to be less stressful on the shingle granule coating than an actual hail storm that would impact the shingles repeatedly over a longer period and more uniformly over roof surfaces (depending on storm duration, wind direction, hailstone size, and the hailstone terminal velocity etc.) than your test.
You did not report the role that aging and repeated thermal heating cooling cycles have on roof shingles, nor the size nor terminal velocity of the ice you shot at your roof shingles.
CONTACT us to suggest technical corrections, additions, or references on hail damage and blister damage to roofing.
To return to the roof blister damage versus hail damage question and summarize:
- Regardless of whether or not there are blisters or blister rash on your roof shingles, if there were pre-existing blisters that were not opened, if there were no visible pits or craters or areas of exposed shingle substrate prior to the hail storm and no significant volume of mineral granules appearing in your roof gutters or on the ground at the ends of downspout leaders before the storm, and if those conditions were in fact observed after the storm, that is a compelling argument for asserting that the damage was caused by the hailstorm.
- A rebutting argument that is plausible is that sometimes people do not notice a pre-existing condition until events make them take a closer look, thus confusing old with new conditions. The assessment of this argument turns on the timing and confidence in earlier observations made of or on a roof.
- You should inspect the roof for the extent of blistering in order to determine if that condition may have been a factor in the extent of damage caused by subsequent hail damage. Using an oblique light when the roof is not in direct bright sunlight should be helpful, as you can see in some of our other photos of roof shingle blister rash.
- Watch out: Indeed foot traffic on roofs, especially in hot weather or on old brittle roof shingles can cause extensive damage. Often we can see on an older roof just where the "inspector" walked by the foot traffic damage, and often we see foot traffic damage concentrated in areas where someone was standing to do work such as around a chimney.
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.
Roof Inspectors: Whose opinion on roof wear do you trust? Avoid 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.
For a professional investigation of hail damage to asphalt shingles, see "Hail Damage to Asphalt Roof Shingles", Timothy P. Marshall, Richard F. Hertzog, Scott J. Morrison, Haag Engineering, Dallas TX.
Convention for roof damage chalk marking codes
In our roof damage photo shown at left, the chalk marks made on the roof by a local inspector were intended to aid in photo-documentation of roof conditions at the time of the inspection, and the inspector opinion about the cause of wear or damage.
To permit close examination and to support those conclusions, sharp closeup macro photographs of the roof surface can often make quite clear the type of roof wear or damage at that site.
- Circle Slash roof damage marking code: the inspector used the circle/slash to show an area of the roof where there was NO damage or loss due to "hail hits" or hail damage - this was a hail damage case. His mark is more or less in the center of interest, and interestingly, in this inspector's case his circle/slash appear to have been made over an area where there was not obvious granule loss, perhaps for comparison with the shingles nearby that did show granule loss.
- "FT" roof damage marking code: by convention some roof inspectors use FT to indicate granule loss or other roof surface damage due to foot traffic or walking-on traffic.
- "HD" roof damage marking code: can be used to mark example areas of roof damage due to hail or ice striking the roof surface
A roof inspector might also use that mark to indicate where they were going to recommend removing a shingle for testing or submission to a manufacturer.
It's SOP for inspectors to use chalk marks to indicate specific observations on a roof that are also to be photographed. Inspectors use chalk usually to mark or indicate the following
- F or R or N,S,E,W are used to indicate the particular roof slope on which the photograph was taken
- Circles, lines, or arrows to indicate roof areas of hail damage or hail hits or mineral granule loss due to scouring or other specific damage to be identified in the roof inspector's report
- SPLT + arrows mark roof areas where there are shingle splits that may be hard to see without up-close access
- R/R or R&R or CUT mark a roof area where a shingle is to be removed (and patched) for independent lab testing
I am not aware of a national standard on roof inspection markings that specifies particular codes or symbols, but we'll continue to research this topic. CONTACT us to report other roof shingle chalk marking schemes used during roof inspections.
Other roof condition details to be photographed and recorded during a roof inspection: rulers & scale indicators
Incidentally, in my own roof inspections I will often place a ruler or other indication of scale in some photographs, and unlike the page top photo repeated just above, I also make closeup macro-photographs that indicate clearly instances of pitting, thermal splitting, mechanical damage etc. I also photograph the entire field of the roof and I prepare comparative photographs of both damaged and un-damaged roof areas and photographs that allow comparison of the condition of roof slopes facing different directions, at different pitches etc.
And a roof inspection is incomplete without a site and building inspection that identify other conditions that might effect the roof. Even a wet or flooding basement or crawl area can have a significant impact on the condition of a building roof, as that moisture moves up through the building and into the attic or roof cavity.
Those details help remove ambiguity or avoid arguments about just what was found in an up-close inspection of roof surface conditions.
Size of Roof Test Square When Reporting Hail Damage
Some inspectors suggest marking off a 10' x 10' test square area and counting the number of hits or marks ascribed to hail damage as a step in assessing the extent of hail damage to a roof. This approach has some sense to it in that it attempts to get past arm-waving speculation about the extent of damage to a roof.
But the roof damage test square approach can have some shortcomings too, depending on how it is applied. Just counting marks indicating hailstone strikes does not adequately consider the depth of damage or the degree to which the roof shingle substrate has been exposed.
And choosing an area for a test square is vulnerable to subjectivity or deliberate skewing of the report results. For example, choosing as a test square a roof slope that was by its orientation less damaged or not damaged at all compared with other roof slopes on the same building will give an inaccurate assessment of the building's roof system.
Hail Damage Resistant Roofing Products
See PLASTIC ROOFING TYPES for examples of impact resistant roof materials.
Some insurance companies offer insurance premium credits for building owners who have installed damage resistant roof shingles or roofing. The Texas Department of Insurance provides information about hail-damage resistant roofing in their article "Products Qualifying for Impact Resistant Roofing Credits" where that source describes two classes of hail damage resistant roofing products:
- Qualified non-metal [roofing] products that resist hail damage. Producers of non-metal roofing that is hail damage resistant include [Web search 5/21/2010]
- Anbrook Industries Ltd.
Pitt Meadows, B.C. Canada
Phone: 604-465-5657
Cedar Wood Shakes - Class 4
Atlas Roofing
Daingerfield, Tx
Phone: 800-270-2852
Asphalt Shingles - Class 4
Certain Teed Corporation
Blue Bell, PA
Phone: 610-341-6678
Web Address: www.certainteed.com
Asphalt Shingles - Class 4
Clarke Group Marketing, Inc.
Mission, B.C. Canada
Phone: 800-663-8707
Western Red Cedar Wood Shakes
and Shingles - Class 3 and 4
Crowe Building Products Ltd.
Ontario, Canada
Phone: 905-529-6818
Web Address: www.authentic-roof.com
Baljen TPO Polymer Roof Tiles - Class 4
Duro-Last Roofing, Inc.
Saginaw, MI
Phone: 800-248-0280
Web Address: www.duro-last.com
PVC Single-Ply Membrane - Class 4
EcoStar, a Divison of Carlisle-Syntec
Carlisle, PA 17013
Phone: 800-211-7170
Web Address: www.ecostar.carlisle.com
Molded Polymer Roof Tiles - Class 4
Elk Corporation of Alabama
Tuscaloosa, AL
Phone: 205-342-0287
Asphalt Coated Fiber Glass Shingles - Class 4
EnviroGard L.L.C.
Tulsa, OK
Phone: 918-299-3540
Marlex Polymer Roof Panels - Class 4
GAF Materials Corporation
Wayne, NJ
Phone: 800-365-7353
Web address: www.gaf.com
Asphalt Shingles - Class 4
G.E.M. Inc.
Calgary, Alberta Canada
Phone: 403-215-3333
Synthetic Slate Roof Tiles - Class 4
Malarkey Roofing Products
Portland, OR
Phone: 800-545-1191
Web Address: www.malarkeyroofing.com
Asphalt Shingles - Class 4
Meeker Cedar Products
Mission, B.C. Canada
Phone: (604) 826-6215
Cedar Wood Shakes and Shingles - Class 3 and 4
New Group Asia Construction Material Supply, Inc.
Houston, TX
Phone: 888-359-2288
Web Address: www.newgroupasia.com
Molded Polymer Roofing Tiles - Class 4
Owens Corning
Toledo, OH
Phone: 419-248-8785
Asphalt Coated Class Fiber Shingles - Class 4
Re-Con Building Products, Inc.
Portland, OR
Phone: 877-276-7663
FireFree Naturals Slate/Shakes - Class 4
Re-New Wood
Wagoner, OK
Phone: 918-485-5803
Phone: 918-485-4687
Recycled Resin Formed Shingles - Class 4
Royal Building Products
Woodbridge, Ontario, Canada
Phone: 1-800-387-2789
Plastic Shingles - Class 4
Silver Creek Premium Products, Ltd
Matsqui, B.C. Canada
Phone: 877-292-3327
Cedar Wood Shakes and Shingles - Class 3 and 4
South20, Inc.
Dallas, TX
Phone: 405-526-6743
Wood Shakes - Class 4
S&W Forest Products Ltd.
Mapleridge, B.C. Canada
Phone: 1-800-806-9663
Cedar Wood Shakes - Class 3 and 4
Teal Cedar Products
Surrey, B.C. Canada
Phone: 888-995 8325
Web Address: www.tealjones.com
Cedar Wood Shakes and Shingles - Class 3 and 4
U.S. Century, L.L.C.
San Antonio, TX
Phone: 877-353-9742
FlexShake, Rubber Shingles - Class 4
Waldun Forest Products Partnership
Maple Ridge, B.C.
Phone: 604-462-8266
Cedar Wood Shakes and Shingles - Class 3 and 4
Watkins Sawmills, LTD.
Mission, B.C. Canada
Phone: 800-663-8301
Cedar Wood Shakes - Class 3 and Class 4
White Mountain Building Products
Payson, AZ
Phone: 928-468-0599
Web Address: www.villageshake.com
Asphalt Shingles - Class 4
- Qualified metal [roofing] products that resist hail damage. Metal roofing materials that meet the UL Standard 2218 are eligible for an insurance discount as of May 1, 1998. They are listed below.
- AEP-SPAN
Dallas, TX
Phone: 800-527-2503
Formed Steel Panels - Class 4
Allmet Roofing Products Division
Division of Metals USA Building Products Canada Inc.
Courtland, Ontario, Canada
Phone: 800-265-9357
Web Address: www.allnet.com
Formed Steel Panels - Class 4
American Roofing Industries
Anitoch, CA
Phone: 925-706-7537
Stone Coated Steel Roofing Panel s- Class 4
Berridge Manufacturing Company
San Antonio, TX
Phone: 800-669-0009
Website: www.berridge.com
Formed Steel Panels - Class 4
Classic Products, Inc.
Piqua, OH
Phone: 800-543-8938
Aluminum Shingle - Class 4
Steel Shingles - Class 4
DECRA Roofing Systems
Corona, CA
Phone: 909-272-8180
Formed Steel Shingles - Class 4
Delta Building Products Ltd.
Delta, B.C., Canada
Phone: 604-953-1000
Aluminum Shingle, Tile, & Shake Panels - Class 4
Steel Shingles, Tiles, & Shake Panels - Class 4
Fabral, Inc.
A Euramax Company
Lancaster, PA
Phone: 800-477-2741
Metal Roof Panels - Class 4
Galvak S.A. de C.V./Galvamet Inc.
Nuevo Leon, Mexico
Phone: 1-888-489-1367 (Joaquin Armendaiz)
Galvatile Steel Roofing Panels - Class 4
Gerard Roofing
Brea, CA
Phone: 714-529-0407
Formed Steel Shingles - Class 4
Great American Manufacturing, Inc.
Houston, TX
Phone: 713-910-2646
Formed Aluminum Shingles - Class 4
Lone Star Metals
Orange, TX
Phone: 409-886-7488
Steel Panels - Class 4
Met-Tile, Inc.
Ontario, CA
Phone: (909) 947-0311
Metal Roof Panels - Class 4
METALWORKS
Moon Township, PA
Phone: 800-320-0101
Formed Steel Shingles - Class 4
Metco Supply
Junction, TX
Phone: 800-258-8378
Metal Roof Panel - Class 4
METROTILE Manufacturing - Metro Roof Products & SteelROCK (MRP)
Oceanside, CA
Phone: 866-638-7648
Formed Steel Panels - Class 4
Prime Building Components LLC
Dublin, TX
Phone: 254-445-3416
Coated Steel Panels - Class 4
Roser Co. Ltd.
Kyongbuk, Korea
J.T. Brown Consulting, Inc.
Laguna Niguel, CA
Phone: 949-362-0508
Stone Coated Steel Panel - Class 4
Copper Panels - Class 4
Sawyer Metal
Tyler, TX
Phone: 903-531-0182
Web Address: www.sawyermetal.com
Metal Roof Panels – Class 4
Southwest Metal Systems, L.L.C.
Mineola, TX
Phone: 903-569-8811
Metal Roof Panels - Class 4
Steel Building Supply
Center, TX
Phone: 888-598-6373
Steel Roof Panels - Class 4
Sweetwater Steel Co., Inc.
Sweetwater, TX
Phone: 800-982-3384
Steel Roof Panels - Class 4
Texas Energy Savers Co.
Joshua, TX
Phone: 817-558-2004
Steel Roof Panels - Class 4
Texoma Steel buildings Inc.
Burkburnett, TX
Phone: 800-686-0742
Coated Steel Panels - Class 4
Titan Metal Roofing Products
Fort Worth, Texas
877-848-2664
Metal Roof Panels - Class 4
Whirlwind Steel Building Systems
Houston, TX
Phone: 800-324-9992
Metal Roof Panels - Class
Frequently Asked Questions (FAQs) about Roof Shingle Hail Damage & how Hail Damage is Distinguished from Blistering, Foot Traffic, or Other Roof Wear, & about Roof Inspection Procedures
Question: Roof inspection procedures: decoding common chalk marks used by roof inspectors to indicate areas of damage or wear
| The photo at page top [and shown again at left] in this web article on roof damage inspections shows a circle with a line drawn thru and FT which I figure is meant to indicate "front". What does the circle with the line indicate? Appreciate your help. - R.B.
Reply: Convention for roof damage chalk marking codes
The chalk marks were made on the roof by a local inspector. In our roof damage photo shown at left and above the circle/slash was an area where the roof inspector opined there was no damage, and the "FT" marked above that spot was being used to indicate granule loss due to foot traffic.
Details about chalk codes used to mark on roofs during inspections and to indicate observations are in the article above at Convention for roof damage chalk marking codes.
|
Question: Expanding the definition of hail damage to include loss of roofing material - not just "dents"
One thing to look at with regards to shingle scouring is if there are any chunks of roofing material (that broke away from the area due to the hail hitting it) left on the surface of the roof after the hail storm. I do not believe that hail damage is only defined as if there was an indentation in the shingle due to the hail. The impact of the hail, in combination with a rapid temperature drop in the shingle due to the icing effect of the hail can cause the shingle to delaminte and loose parts of the shingle when impacted by a hail stone. - Martin Rizzo 6/21/11
Reply:
Thanks for the helpful comments about hail damage Martin. What you say makes a lot of sense. We agree.
Question: resolution of hail damage case?
Is it known whether this man and his situation with blisters vs hail damage mentioned above ever won his case with his insurance co? I too have the same problem. - Tom McLaughlin 8/22/11
Reply:
No Tom, we have not had more feedback, though the case described above was unusually well documented.
Question: Phoenix hail storm - inspector claims damage due to weather and acid from bird droppings
There was a hail storm in Phoenix, AZ, in October 2010. I was out of the country at the time. I have returned in April 2012. I am in the process of determining if there were hail damage on my roof currently. The insurance inspector claim there was no hail damage on the roof except on the AC condenser and some of the window screen. The inspector claimed the damages seen on the roof were mainly due to weather and acid from the bird dropping. Is is possible for me to send some photos to you to obtain your opinion? Thank you in advance for your time and help in this matter. - PSF Chan 5/24/12
Reply:
xI'd like to see some sharp photos both of the whole roof, all slopes, and of the slope where the damage seems apparent to you, and sharp closeups of the shingle damage area details. Use the CONTACT US link found on any website page.
Question: What about other roof products that are more resistant to hail damage
Why are there no concrete roof tile products mentioned under hail resistant roofing? Are they not more durable than asphalt shingles? - Robert Joseph 7/10/12
Reply:
Robert, we agree that concrete roof tiles are more hail resistant than thinner softer products such as asphalt shingles. This article is about recognizing hail damage to asphalt shingles and distinguishing hail damage from other types of asphalt roof wear such as granule loss, blistering, foot traffic, cracking, &c. The issue of distinguishing hail from other wear on concrete roof tiles has not arisen, though I speculate that in extreme cases such as baseball sized hail that occurs in some locales, all roof materials, including concrete, tile, slate and stone can suffer damage as well. See Hail Damage Resistant Roofing Products.
Question: when is entire roof replacement vs just individual shingle repacement justified ? How many hail stone hits per square justify a new roof.
What warrants replacement of entire roof versus repairing only damage shingles from hailstones? How many hail stone hits per square warrant entire roof replacement? Thanks - Anon
When testing for hail stone hits, how do you conclude which area to test? From an adjuster's view, do you choose the best square or most damaged square? - Anon
Reply:
If the roof is worn out and leaking it needs replacement;
If the roof has been hail-scoured but is not leaking and not at immediate end of life in the view of an unbiased expert, then replacing it is not appropriate nor cost justified. If I were an insurance adjuster, in my OPINION, I would consider giving a pro-rated allowance for hail damage on a roof by figuring out
- the roof's remaining life before the hail damage occurred (infer this by examining non-scoured shingles or non-scoured roof slopes as often hail is directional and so damage is not at all uniform)
- the estimated reduction in remaining roof life because of the hail damage
- if some slopes were not hail damaged at all I'd exclude them from the adjustment
I don't think the answer to amount of damage is based on number of stone hits per square, but rather, we should look carefully at the shingles to see the total extent of granule loss over the whole roof, and the DEPTH of granule loss on shingles, and in particular, if there is bald shingle substrate exposed on shingles, those individual shingles have a short remaining life (to be more specific we need to consider slope, age, climate and other factors).
Example:
If I inspect a roof with 10% (or some other TBD %) of the shingles on a given slope having 1/4 to 1/2" absolutely bald spots on the shingles, showing the shingle substrate, for an organic OR fiberglass shingle, in my opinion the safe reliable remaining life of that roof slope is less than 5 years. As an insurance adjuster (which I am not, though I do advise insurers and adjusters as a neutral professional), in deciding to offer an allowance and to encourage roof replacement within that period, I would be considering also a wish to reducce or even avoid the risk of a future property loss due to a roof leak on a roof that should have been replaced sooner.
I welcome debate on these questions in order to arrive at as consistent and fair an assessment procedure as we can.
...
Ask a Question or Search InspectApedia
Questions & answers or comments about Roof Shingle Hail Damage & how Hail Damage is Distinguished from Blistering, Foot Traffic, or Other Roof Wear, & about Roof Inspection Procedures.
Ask a Question or Enter Search Terms in the InspectApedia search box just below.
Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
- [1] Argonne National Laboratory, Office of Science, U.S. Department of Energy, "Vertically Shot Bullet Landing Speed", Michael R. Rayno (Rev), Argonne National Laboratory, Building DEP/223 9700 S. Cass Ave. Argonne, Illinois 60439-4845 USA, This article provides calculations and examples of the terminal velocity of a hailstone. Web search 03/14/2011, original source: http://www.newton.dep.anl.gov/askasci/phy05/phy05051.htm
Quoting:
HAILSTONE: A spherical hailstone weighing 10 gm has a volume of
10 cm^3 since the density is
1 gm/cm^3. REALITY CHECK: The volume = 10 cm^3 = 4/3 *pi* r^3. So
r^3 = 2.4 cm^3 or a radius of r = 1.3 cm or a diameter of 2.6 cm (a
fairly nominal hailstone -- about an inch in diameter).
The potential energy of a hailstone weighing 10 gm = 10^-2 kg
falling from 10 km is: P.E. = m*g*h =
10^-2 * 9.8 * 10,000 (about 10^-2+1+1 = 10^0 = 1 Joule). Its velocity
assuming complete conversion of the P.E. to K.E. = 1/2*m*(v)^2
gives: 1 = 1/2x10^-2*(v)^2 or v^2 = 200 m^2 or about 15 m / sec
- "Products Qualifying for Impact Resistant Roofing Credits", Texas Department of Insurance - see http://www.http://tdi.state.tx.us/home/roofingx.html
- [2] "Roofing: Premium Credits Product Listing, Roofing Products Eligible for Discount", State Farm Insurance 5/1/2010 - Web Search 07/12/2010, original source http://www.statefarm.com/_pdf/nationwide.pdf [copy on file as /roof/State_Farm_Premium.pdf]
- [3] 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
- [4] 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
- [5] Arlene Puentes, a licensed home inspector, educator, and building failures researcher in Kingston, NY
- [6] "Hail Damage to Asphalt Roof Shingles", Timothy P. Marshall, Richard F. Hertzog, Scott J. Morrison, Haag Engineering, Dallas TX,
- [7] Greenfeld, S.H., 1969: Hail resistance of roofing
products, Building Science Series #23, National
Bureau of Standards, 9 pp.
Koontz, J.D., 1991: The effects of hail on residential
roofing products, Proc. of the Third International
Symposium on Roofing Technology, NRCA/NIST,
206-215.
- [8] Marshall, T. P., and R. F. Herzog, 1999: Protocol for
Assessment of Hail-Damaged Roofing, Proc. of the
North American Conf. on Roofing Technology,
Toronto, Canada, p. 40-46.
- [9] Marshall, T.P, R.F. Herzog, S.J. Morrison, and S.R.
Smith, 2002. Preprints, 21st Conf. on Severe Local
Storms, San Antonio, TX, Amer. Met. Soc., 95-98.
- [10] Morrison, S.J., 1999: Long-Term Effects of Hail on
Asphalt Composition Shingles Proc. of the North
American Conf. on Roofing Technology, Toronto,
Canada, 30-39.
- [11] Ribble, R., D. Summers, R. Olson, and J. Goodman:
From generation to generation: issues and problems
facing the steep-slope roofing industry. Proc. of the
10th Conf. on Roofing Technology, 1-5.
- [12] "Roofing: Premium Credits Product Listing", State Farm Insurance, - Web Search 07/12/2010 original source http://www.statefarm.com/_pdf/nationwide.pdf
- [13] Asphalt Roofing Residential Manual,
- [14] Building Pathology, Deterioration, Diagnostics, and Intervention, Samuel Y. Harris, P.E., AIA, Esq., ISBN 0-471-33172-4, John Wiley & Sons, 2001 [General building science-DF] ISBN-10: 0471331724
ISBN-13: 978-0471331728
- [15] Building Pathology: Principles and Practice, David Watt, Wiley-Blackwell; 2 edition (March 7, 2008)
ISBN-10: 1405161035
ISBN-13: 978-1405161039
- [16] Built-Up Roof Systems, Manual, C.W. Griffin, Mcgraw-Hill (Tx); 2nd edition (July 1982), ISBN-10: 0070247838, ISBN-13: 978-0070247833
- [17] Green Roof Construction and Maintenance, Kelley Luckett, McGraw-Hill Professional, 2009, ISBN-10: 007160880X, ISBN-13: 978-0071608800, quoting: Key questions to ask at each stage of the green building process Tested tips and techniques for successful structural design
Construction methods for new and existing buildings
Information on insulation, drainage, detailing, irrigation, and plant selection
Details on optimal soil formulation
Illustrations featuring various stages of construction
Best practices for green roof maintenance
A survey of environmental benefits, including evapo-transpiration, storm-water management, habitat restoration, and improvement of air quality
Tips on the LEED design and certification process
Considerations for assessing return on investment
Color photographs of successfully installed green roofs
Useful checklists, tables, and charts
- [18] Low Slope Roofing, Manual of, 4th Ed., C.W. Griffin, Richard Fricklas,
McGraw-Hill Professional; 4 edition, 2006, ISBN-10: 007145828X, ISBN-13: 978-0071458283
- Roof failure causes in depth (and specific methods for avoiding them)
- Roof design fundamentals and flourishes, based on voluminous industry research and experience
- New technologies and materials -- using them safely and correctly
- Comprehensive coverage of all major roofing systems
pecifications, inspection, and maintenance tools for roofing work
- [19] Metal Roofing, an Illustrated Guide, R.A. Knowlton , [metal shingle roofs],
- [20] Problems in Roofing Design, B. Harrison McCampbell, Butterworth Heineman, 1991 ISBN 0-7506-9162-X (available used)
- [21] Roofing The Right Way, Steven Bolt, McGraw-Hill Professional; 3rd Ed (1996), ISBN-10: 0070066507, ISBN-13: 978-0070066502
- [22] Smart Guide: Roofing: Step-by-Step Projects, Creative Homeowner (Ed), 2004, ISBN-10: 1580111491, ISBN-13: 978-1580111492
- Solar heating, radiative cooling and thermal movement: Their effects on built-up roofing (United States. National Bureau of Standards. Technical note), William C Cullen, Superintendent of Documents, U.S. Govt. Print. Off (1963), ASIN: B0007FTV2Q
- [23] Tile Roofs of Alfred: A Clay Tradition in Alfred NY
- [24] "Weather-Resistive Barriers [copy on file as /interiors/Weather_Resistant_Barriers_DOE.pdf ] - ", how to select and install housewrap and other types of weather resistive barriers, U.S. DOE
- ...
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
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