Fishmouth Curling on Asphalt Shingle Roofs

CURLING ASPHALT SHINGLES - Asphalt roof shingle fishmouthing, photographs, cause, prevention
- Comparing fishmouthed shingles and curled roof shingles
- Questions for diagnosing a premature roof shingle wear-out failure
- Types & photographs of organic felt asphalt roof shingle defects & failures
Questions & answers about roof shingle fish mouthing & curling
References

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This website tells readers how to identify & explain the asphalt shingle roof wear pattern known as "fishmouthing" or "fishmouthed roof shingles".

Fishmouthing Asphalt Shingle Explanation & Photos

Here we discuss the fishmouth failure pattern, its cause, its evaluation as a sign of roof wear and other problems, and how to prevent this condition. We contrast the shingle fishmouth failure pattern with shingle curling failure patterns. Our page top photograph of a fishmouthed shingle roof.

These defects occur on organic-mat or fiberglass-mat asphalt roof shingles. Common shingle failure factors include improper storage and handling of the asphalt shingles before installation, improper nailing, improper flashing (which pertains to any roofing material), and defective asphalt shingle product material leading to thermal splitting, cracking, blistering, staining, and in some cases curling or cupping 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.

Fishmouthed roof shingles wear in the unique raised "mouth" shape shown in photographs on this page.

Just as in the case of other shingle cupping or curling patterns, this raised portion of the shingle is vulnerable to damage from foot traffic, but unlike the other cupping or curling patterns, fishmouthed roof shingles are not simply an age or wear indicator on the roof.

They indicate a combination of roof moisture and a roof ventilation defects.

An example of the less-than-fully-waterproof back of asphalt roof shingles is seen in our photos of "fishmouthed" roof shingles. In these cases a specific "curling" pattern of shingles called "fishmouthing" displays a raised shingle edge which looks a lot like a fish's open mouth. These shingles are not curled over at the very edge.

Fishmouthing wear pattern on asphalt roof shingles

The location of fishmouths on roof shingles is predictable and diagnostic: if inspected closely the shingles will show that this pattern of raised open lower shingle edges will occur first and worst over the shingle butt joints where individual shingle sides abut one another.

In the photo above, you can see even from the ground that the shingles were "laddered" onto the roof rather than being staggered in a stair step pattern when they were installed!

So the pattern of "fishmouths" on the roof may be regular, following a diagonal or a ladder pattern depending on how the shingles were nailed on the roof.

In the fishmouthed shingle photo just above-left you can see that shingles were staggered during installation on the roof, not laddered.

Inadequate Venting and High Building Moisture Cause of Asphalt Shingle Fishmouthing

Fishmouthed cupping of asphalt roof shingles is caused by excessive under-roof moisture such as by a poorly or un-vented attic or roof cavity. Moisture escaping through the roof sheathing and up through the bottom of the shingles contacts the uppermost shingle which spans the butt joint of shingles below, placing more moisture at that point on the shingle tab than elsewhere. This uneven moisture, probably combined with weather exposure, leads to a raised, cupped "fishmouth" look on those shingles.

Shingles are not quite waterproof: You may not realize it but asphalt roof shingles are not quite waterproof and in particular the back side of asphalt shingles is much less water resistant than the upper or exposed side. The exposed side of an asphalt shingle is protected from sun damage by a coating of mineral granules. These shingles rely on the pitch of the roof and mechanical drainage combined with proper placement or pattern of shingling on the roof to avoid leaks. [This photo courtesy of Carl Gerosa, New Rochelle, NY.]

Shingle Fishmouthing is a Building Diagnostic Aid

I took this photograph of fish mouthed roof shingles as a great example of how they diagnose other building conditions. This was a car wash - talk about a lot of interior moisture in a building! There was also no roof venting system of any consequence on the building.

So fishmouthed roof shingles mean that there has been a combination of high interior building moisture, (maybe from a wet basement or a flood?) combined with poor or inadequate under-roof ventilation.

Unlike other more normal wear patterns on asphalt roofs, such as curling, cupping, or even some cracking or granule loss patterns, fishmouthing tells us something more about the building itself and its leak, moisture, and venting history and design.

Fishmouthed Asphalt Roof Shingles under light snow cover - an Ice Dam, Leak, Mold, Rot Warnings

Because the raised "fishmouths" on asphalt shingles show up above and through a light snow cover, this is one roof pattern, wear indicator, and sign of both moisture and bad roof venting design that you might be able to diagnose from the ground under some conditions.

This is an important condition to notice because the same inadequate under-roof venting that was a factor in the creation of these fishmouths on the roof surface may also have led to ice dam problems on the same building. In turn, ice dams may have led to leaks into attics, ceilings, or building walls.

In turn, leaks into building walls might have led to a hidden mold problem on the building. So those fishmouthed shingles might actually be a fair predictor of mold problems on some buildings and if other factors or complaints are present, might be a reason to explore the building wall cavities under the roof eaves, looking for evidence of leaks, mold, rot, or insect damage where otherwise we might not feel that such invasive measures were justified.

Fishmouthed Asphalt Shingles are Vulnerable to Damage

As we suggested in the cased of other cupped, curled, or fragile asphalt roof surfaces, we would stay off of fishmouthed-shingle roofs, particularly in cold weather (when the fishmouthed roof shingles are more likely to break). If we have to walk on a fishmouthed shingle roof, tiptoe carefully, avoiding stepping on the raised or fishmouthed shingle sections.

Do Fishmouthed Asphalt Shingles Need Replacement?

If the shingles are not damaged, broken, cracked, or showing other signs of wear, it may be possible to leave these shingles on the roof longer than otherwise. That's because this fishmouth pattern can show up earlier in shingle life on a wet building with poor under-roof venting. An experienced inspector or roofer can point out the extent of roof damage and other shingle wear signs that will decide if the roof is ready to be replaced.

Six Year Old Roof Fishmouthing Failure? Shingle Curling & Granule Loss Diagnosis & Commentary

Fishmouthed roof shingle fail(C) Daniel Friedman

Question about early asphalt roof shingle failure:

I live in Wisconsin and had my roof replaced (total strip down) about 6 years ago. Now my shingles are curling up or fish mouthing. I do not know what you call it but it looks terrible . Can you help me out? A friend said to check on the internet for something with Owens Corning.

I believe they are 30 yr shingles. I do not have any of the paper work but when they put them on they said they only use premium shingles. Check out the rain gutter. It is 3/4 full of shingle fragments and granules. The rest of the roof shingles still look good. Any help would be great. - Louis Tolley, Adams WI

Answer and advice on diagnosing a failing fishmouthed shingle "new roof" job:

The roof shingle wear pattern in your photos is easily mistaken for "fishmouthing asphalt roof shingle" but what we see in your photos is not "fishmouthing" but rather shingle curling, combined with extreme granule loss.

Comparing Shingle Fishmouth Patterns with Shingle Curling Patterns

Fishmouthing asphalt shingles appear as an upwards curve in the center of shingle tabs, usually where the center of a fishmouthed shingle tab crosses over the shingle butt joints in the course below. See the fishmouth shingle photos above on this page.

Shingle tab curling, such as shown in your photos, occurs at the corners of shingle tabs, not in the center of the tab. See CURLING ASPHALT SHINGLES.

How old is This Roof Wear-Out?

Regardless, your roof photos show severe wear and curled shingle tabs that we see at the end of roof life - your photos of this worn roof slope show that every single shingle tab is curled up from a corner – that combined with the significant granule loss would be very unusual on a six-year-old roof. We comment further and provide some roof failure diagnostic questions just below.

From looking at the photographs, and recognizing that we are not looking at the entire roof, some comments and questions arise that should help sort out this "early roof failure" mystery:

The roof slopes in your photographs are totally worn out
This does not look like a six year old roof
Your comments suggest that other roof slopes are fine.
Before we assume that the wear difference is due to the building, roof ventilation, weather exposure, or a similar cause, let's conside that the roof is reported to be just six years old - actually we wonder if that's quite right.

Six-Year-Old Roof Shingle Failure Diagnostic Questions

Watch out: First off - don't fall off the roof while you are up there looking around.

Don't walk on these fragile, damaged asphalt shingles - they'll break and leak.

Go back to look at your information on your 6 year old re-roof job with the questions listed below. If you have no records and no documentation of who did the roof, what was the contracted scope of work (all slopes or just some) we can still figure this out by inspection of the whole building.

What type of shingles were installed in your re-roof job six years ago (your photos of failing shingles look like organic base not fiberglass base)
Are the same type of shingles present on all roof slopes?
Were all the roof slopes re-roofed or just some slopes? Sometimes only the worst or actively leaking roof slope is replaced, especially if the homeowner is squeezing for the lowest re-roof price, money is tight, or the roofer feels that there are five or more years remaining on other roof slopes
Did anyone actually inspect the roof before and after the job, other than the roofer?
Do all of your roof slopes look the same? That is, is the shingle wear the same on all slopes?
Are all roof slopes exposed to similar wind and weather conditions ? Usually not - which slope(s) show the most shingle wear?
Are you sure the roofer actually replaced shingles on all of the slopes?
Did you actually see that work being done?
If you remove or lift one of these bad shingles at the roof edge, do you see raw roof deck below or other old shingle layers?
Other asphalt shingle roof wear indicators and conditions (besides fishmouthing) are discussed beginning at ASPHALT ROOF SHINGLES.

Usually when we have inspected early roof failure cases like this it turns out that there was a misunderstanding (or less often, dishonesty) - the roofer did not re-shingle all slopes, maybe just one of them, but the owner thought they all were being done.

Frequently Asked Questions (FAQs) about the fishmouth curling pattern on asphalt roof shingles: causes, cures, prevention

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Technical Reviewers & References

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ASPHALT ROOF SHINGLES
  ASPHALT SHINGLE DEFINITIONS
  ASPHALT SHINGLE FAILURE TYPES
  ASPHALT SHINGLE INSTALLATION
  ASPHALT SHINGLE LIFE / WEAR FACTORS
  ASPHALT SHINGLE PROPERTIES
  ASPHALT SHINGLE RE-ROOF GUIDE
  ASPHALT SHINGLE UNDERLAYMENT SPECS
  ASPHALT SHINGLE VALLEY FLASHING
  ASPHALT SHINGLES on VERY STEEP ROOFS
  ALGAE, FUNGUS, LICHENS, MOSS COMPARED
  ALGAE STAINS ON ASPHALT ROOF SHINGLES
  ALGAE STAIN TEST METHODS
  ALGAE, FUNGUS, LICHENS, MOSS on SHINGLES
  BLACK STAIN REMOVAL & PREVENTION
  BLISTERS on ASPHALT SHINGLES
  CELLOPHANE STRIP REMOVAL?
  CRACKS in FIBERGLASS SHINGLES
  CUPPING ASPHALT SHINGLES
  CURLING ASPHALT SHINGLES
  EARLY ASPHALT SHINGLE FAILURE
  EXTRACTIVE BLEEDING on SHINGLES
  FISHMOUTHING ASPHALT SHINGLES
    FISHMOUTHING ASPHALT SHINGLE EXPLANATION
    EARLY ROOF FAILURE DIAGNOSTIC QUESTIONS
  GRANULE LOSS from SHINGLES
  HAIL DAMAGED SHINGLES
  LADDERING & STAIR STEPPING SHINGLES
  LIFE / WEAR FACTORS in SHINGLES
  MECHANICAL DAMAGE of SHINGLES
  MOSS & LICHENS on SHINGLES
  ORGANIC FELT SHINGLE DEFECTS
  SPLICE DEFECTS on ASPHALT SHINGLES
  STAINS on ROOF SHINGLES
  WHAT ARE ASPHALT SHINGLES
  WIND DAMAGE to ROOFS

Thanks to reader Louis Tolley, Adams WI , for discussing fishmouthed roof shingles, early failure of a new roof, and for photographs of fishmouthed roof shingles - July 2010
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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Asphalt Roofing Residential Manual,
Built-Up Roof Systems, Manual, C.W. Griffin, Mcgraw-Hill (Tx); 2nd edition (July 1982), ISBN-10: 0070247838, ISBN-13: 978-0070247833
Concrete Folded Plate Roofs, C. Wilby PhD BSc CEng FICE FIStructE (Author), Butterworth-Heinemann, 1998, ISBN-10: 0340662662, ISBN-13: 978-0340662663
Problems in Roofing Design, B. Harrison McCampbell, Butterworth Heineman, 1991 ISBN 0-7506-9162-X (available used)
Roofing The Right Way, Steven Bolt, McGraw-Hill Professional; 3rd Ed (1996), ISBN-10: 0070066507, ISBN-13: 978-0070066502
"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
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