Organic Felt Asphalt Roof Shingle Defect Recognition, Diagnosis, & Repair

ORGANIC FELT SHINGLE DEFECTS - Types & photographs of organic felt asphalt roof shingle defects & failures
- Asphalt roof shingle granule loss, photographs
- Asphalt roof shingle cupping, curling, fishmouthing, photographs
- Asphalt roof shingle blisters and splices, photographs
Questions & Answers about the life expectancy & defects found on organic felt asphalt shingle roofs
References

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Guide to asphalt shingle roofing: this article series explains how to identify & explain the most-common asphalt roof shingle failures and how to obtain asphalt roofing shingle failure claims assistance. 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.

Storm damage from wind and hail occur and need to be distinguished from defective asphalt shingle product or asphalt shingle installation errors. 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.

ORGANIC FELT SHINGLE DEFECTS - Organic-mat-based Asphalt Roof Shingle Wear & Failures

"Organic felt" roof shingles refers to using cellulose (paper) as the substrate on which the shingle is constructed. The cardboard or cellulose shingle mat is impregnated with hot asphalt and coated with mineral granules to form a sunlight and weather resistant upper surface.

By contrast, at CRACKS in FIBERGLASS SHINGLES we discuss a previous history of thermal splitting of fiberglass-mat-based asphalt roof shingles.

Also see ASPHALT SHINGLE PROPERTIES and see Choosing an Asphalt Shingle: Organic vs. Fiberglass, Ted Cushman, The Journal of Light Construction, May 1993 for more about the debate around the advantages and disadvantages of organic mat asphalt shingles vs. fiberglass mat-based asphalt roof shingles.

Mineral granule loss from asphalt roof shingles - details are at GRANULE LOSS from SHINGLES

This photograph shows severe loss of mineral granules from an asphalt shingle roof. This 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. Anywhere that a shingle has lost the protection of its mineral granules that shingle has a reduced life expectancy.

In all climates the loss of granules from an asphalt shingle or mineral-covered roll roofing roof 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:

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.
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: 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.
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,

Roof shingle fragility and damage risks

We recommend that inspectors stay off of cupped-asphalt shingle roofs, particularly in cold weather (shingles are more likely to break).

If we absolutely have to walk on a cupped shingle roof, we would tiptoe carefully, avoiding stepping on the raised or cupped shingle sections, or if doing repairs, we would prop a ladder up off of the roof surface and work from that scaffold as is sometimes done with slate or other fragile roof surface repairs.

Is Roofing Felt Underlayment Needed Under Asphalt Roof Shingles?

While the requirement for felt underlayment beneath asphalt roof shingles seems to be a topic of almost timeless argument subject to much arm-waving and little reading of manufacturer's instructions and warranties, various sources recommend or require installation of a felt underlayment over the roof deck before asphalt roof shingles are installed.

Booth & Roberts reported at length on the uses of underlayments on asphalt shingle roofs, citing (quoting):

Asphalt shingle underlays are commonly used throughout North America. The National Roofing Contractors Association’s (NRCA’s) definition of underlay(ment) includes some important functions:

To separate the roof covering from the roof deck
To shed water
To provide secondary weather protection

The authors point out that

"Resins from green lumber roof decks have been known to interact with roof shingles, and a separation layer of underlay can be useful. Underlays are quickly applied and they can provide temporary roofing before the roof shingles are installed. Underlays have remained intact after shingles have blown away, thereby providing temporary roofing [7]. Underlays provide secondary weather protection in ice-dam situations, when water backs up over the head-laps of shingles.

Other functions of underlays have been reported [8]. Two of the more important ones are air-flow resistance and moisture storage. Air-flow resistance reduces windblown water penetration from the outside and moist air penetration from the inside of a roof. Moisture storage provides temporary storage for small amounts of leak water, which subsequently evaporates in dry weather. We know of no experiments that quantify these advantages.

There are disadvantages to underlays. Felt materials can wrinkle and buckle, and these imperfections can telegraph through the finished shingle layer [8,9]. Peterson reported that underlays reduced the life of roof shingles in California due to heat build-up [10]. Explaining how an underlay will act as secondary weather protection when it has shingle nails through it every 8 inches (203 mm) or so can be a challenge. The liquid water transmission test in ASTM D 4869 for asphalt felt underlayments for shingles [11] includes the following note: “Take care to ensure that the staples do not protrude at the front surface of the plywood board so as not to puncture the test specimen,” this is hardly realistic. Slipperiness and poor ultraviolet (UV)"

NRCA, Building Code, & Manufacturers Recommend or Require Felt Underlayments on Shingle Roofs

Booth & Roberts also report that [Reference numbers are to references in the cited document.]

NRCA: NRCA recommends underlays on all shingle roof systems without exception [1]. A 1990 survey indicated that 79 percent of U.S. roofing contractors always used underlays [12].

Roof Warranty: The absence of underlays can invalidate some manufacturers’ warranties and roof system fire classifications [13].

Canadian building codes do not require general (full roof) underlays under roof shingles. Many Canadian roofing contractors use general underlays, while others do not. Typically, underlays are used more over wood plank roof decks and less over plywood. Underlays are more likely to be used on lower-sloped roof systems than on steeper sloped roofs. There also are provincial preferences, for example, Ontario roofing contractors tend to use underlays less than their neighbors in Québec.

Inadequacy of Roofing Felt as a Vapor Barrier for Asphalt Shingles in Hot Humid Climates?

A Building Sciences Corporation report also elaborates the usefulness of placing a vapor barrier on the roof deck below shingles in hot humid climates. BSC points out that: [some paraphrasing -DF]

Unvented roofs with asphalt shingles in hot humid climates require a vapor barrier between the asphalt shingles and the roof deck. This is because asphalt roofing materials store water from dew or rain. Thus asphalt shingles form a water reservoir not unlike wood shingle or shake roofs. The report argues that this stored moisture is driven inwards [presumably as water vapor, not liquid water] when sun strikes the damp or wet roof surface, and it continues to argue that moisture is driven through vapor-permeable roofing paper, felt, and plywood or OSB roof decking, thus ultimately into the attic space

But unlike an asphalt shingle roof nailed [over felt] directly to a roof deck, a wood shingle or shake roof that has been installed using best practices includes a disposal path for water absorbed in the roof surface: an air space between the wood roofing and the roof deck, or the installation of wood roofing over spaced nailers or "skip sheathing".

In cool or temperate climates this does not present a problem because the combination of heavy wetting from due or rain i snot combined with solar heating at high outdoor temperatures, say the authors who go on to argue that that buckled roof shingles observed in the morning (caused by moisture migrating back up from the roof deck) relax during the day. But on an un-vented roof moisture driven inwards [through the shingles, roofing felt, and OSB or plywood roof decking] in hot humid climates, needs to be addressed.

This phenomenon can typically be ignored in climates other than hot humid climates because the combination of extensive dew formation and solar heating at high outside ambient temperatures is not common. In vented roofs, this is often manifested in the buckling of shingles early in the morning as the moisture migrates in to the roof deck sheathing and the joints close. This is followed by relaxation and opening up of the roof sheathing later in the day—the buckling disappears.

But in un-vented roofs in hot humid climates, the authors argue that water from the roof surface is drawn upwards in liquid form, by capillary action, between plies of overlapped shingle courses where it passes ultimately through the vapor barrier and through the roof decking to the roof cavity interior.

The driving force of moisture through the roof and into the building is by solar heating according to the authors.

[OPINION-DF: from exterior roof inspections at all times of day and seasons, we have not observed this time-related morning roof shingle buckling in the Northeastern U.S. nor in Florida, nor the Southwest, though the authors report the phenomenon. It is possible that the authors are not quite correct that daily buckling and relaxing of roof shingles can be ignored on a vented roof as harmless, since certainly the product is expected to remain flat, and flexing daily might reduce its anticipated wear life.]

With unvented roof assemblies, this inwardly driven moisture must be addressed. The preferred method is to prevent the moisture from entering the roof deck material via the installation of a vapor barrier.

[OPINION-DF: we argue at ROOF VENTILATION SPECIFICATIONS that un-vented roofs are not a best building method in any climate.]

Asphalt shingles are quite impermeable to the passage of liquid water directly through them. However the geometry of their installation allows wicking at overlaps. This inwardly driven capillary water is the source for the wetting of the roofing underlayment and roof sheathing. The material properties of shingles change under elevated temperatures and moist conditions due to their hygroscopic nature. The large vapor pressures resulting from incident solar radiation and the changed material properties are sufficient to drive moisture inward through the shingles. Roofing felts or underlayments vary greatly in their permeability to water vapor; the typical underlayment used under asphalt shingles in residential construction is quite permeable.

[QUESTION-DF: we note that the test chamber constructed by BSC was itself in an enclosed, air-conditioned space, and that the underside of the test chamber roof was at least in part exposed to the air conditioning. It seems possible that the reduced humidity and lower temperatures on the "interior-side" of the test roof may have contributed to moisture behaviors that vary from what occurs in the field. Attics and under-roof spaces such as in an un-vented "hot roof" cathedral ceiling are certainly not exposed to cool dry conditioned air. BSC may have addressed this concern but we did not find it in the referenced article.

The conclusion of the BSC report is an argument for installation of an impermeable moisture barrier underneath roof shingles, perhaps in place of the traditional and permeable roofing felt.

[QUESTIONS-DF:

What are the differences between the test roof and a roof's behavior in the field?
How does the impermeable moisture barrier under roof remain impermeable when perforated by shingle nails or staples? What will be the market effects of suggesting entire roofs be underlaid first with a moisture barrier unaffected by roof shingle fasteners such as ice and water shield?
Why not recommend that all roofs and roof cavities include ventilation in their design, not only solving the possible driven-moisture problem discussed by BSC but also providing for longer shingle life (cooler roof surface) and in cooling climates, possibly reduced building cooling costs?]

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Technical Reviewers & References

Related Topics, found near the top of this page suggest articles closely related to this one.

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.
Carl Gerosa, New Rochelle, NY.
"The Uses and Performance Requirements of Steep-Slope Roof Underlays in North America and the United Kingdom", Robert J. Booth, Keith Roberts, Proceedings of the North American Conference on Roofing Technology, p. 112-118 - Web Search 07/12/2010. This scholarly article cites 33 research articles on the role of roofing underlayments.
"Unvented Roofs, Hot- Humid Climates, and Asphalt Roofing Shingles Research Report - 0306 Feb-2003 Building Science Corporation", Building Science Corporation, 30 Forest Street, Somerville, MA 02143
Quoting from the article abstract: "When constructing unvented roofs with asphalt shingles in hot-humid climates, a vapor barrier must be installed between the asphalt shingles and the roof deck." - Web Search 5/21/2010
NRCA Roofing & Waterproofing Manual, 5th Edition, National Roofing Contractors Association, 10255 W. Higgins Road Suite 600 Rosemont, IL 60018-5607 Telephone: (847) 299-9070 Toll Free: (866) ASK-NRCA (275-6722), e-mail: info@nrca.net. - http://www.nrca.net/rp/pubstore/details.aspx?id=243&c=9
"Choosing an Asphalt Shingle: Organic vs. Fiberglass", Ted Cushman, The Journal of Light Construction, May 1993, pp. 11-14. Used with Permission from the Journal of Light Construction.
The Journal of Light Construction has generously given reprint permission to InspectAPedia.com for adaptations, quotations, or reproductions used at this website. All rights and contents of the JLC material are ©Journal of Light Construction and may not be reproduced in any form.
Asphalt Roofing Residential Manual,
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
Building Pathology: Principles and Practice, David Watt, Wiley-Blackwell; 2 edition (March 7, 2008) ISBN-10: 1405161035 ISBN-13: 978-1405161039

Cupping Asphalt Shingle Explanation & Photos

Please see CUPPING ASPHALT SHINGLES for the full text of this article.

Asphalt roof shingles often show cupping (a concave center), curling (raised edges which curl downwards), and fishmouthing (raised edge of a shingle tab at its center with little curling). Each of these is discussed below.

Cupping asphalt roof shingles (see photos below), particularly on organic or felt-based asphalt shingles, are a normal wear pattern that shows up with shingle age.

This "normal" cupping or curling pattern will display shingles which are concave in their center, with the corners and possibly the three exposed shingle tab edges curled such that the very edge of the shingle curls downwards.

Shingles in this condition are fragile and nearing end of life. In this condition, if someone walks on cupped shingles the raised cupped sections will break and can lead to early failure and leaks.

Curling Asphalt Shingle Explanation & Photos

Please see CURLING ASPHALT SHINGLES for the full text of this article.

Curling roof shingles (see photos below) will show a curling-under at the edges of the shingle tab, first at the lower edge and sometimes also at the two sides of the shingle tab.

In fact we have seen a "failed" roof that was not leaking until the fellow who was asked to inspect it walked across this fragile surface.

From a ladder at the roof edge one could clearly see the virtual footprints of broken shingle edges where the "inspector" had walked. It's best to stay off fragile roof surfaces to avoid converting a "near end of life" condition to a "failed, leaking" condition.

Curling and cupping may occur together on the same roof, or shingles may appear to be curled-only (or fishmouth-curled-only as you'll read next). We don't see cupping without some curling.

Fishmouthing Asphalt Shingle Explanation & Photos

Please see the full text of this article at Fishmouthing Asphalt Shingles.

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. [Photo: Carl Gerosa]

Fishmouthed asphalt roof shingles: An example of the less-waterproof back of asphalt roof shingles is seen below in our photo of "fishmouthed" roof shingles. In these cases a specific "curling" pattern of shingles called "fishmouthing" is not simple age and wear. This pattern displays a raised shingle edge (it's not cupped over at the very edge) which, if inspected closely, will typically occur first and worst over the shingle butt joints where shingle sides abut one another.

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.

Laddering and stair-stepping of roof shingles

Please see LADDERING & STAIR STEPPING SHINGLES for the full text of this article.

The photograph shows a sloppy "ladder pattern" installation of strip-type asphalt shingles. While opinions (and expertise) vary among roofers, this ladder pattern shingle application may not be as durable a roof installation as one which staggered the shingle offsets more than a single six inches (or in this case only 3") left and right with each shingle course.

On other asphalt shingle roofs, particularly older ones, you may notice that the pattern of fishmouth occurrence on an asphalt shingle roof follows a fairly regular or stair-stepped pattern, or it may follow a regular "ladder" like pattern up the roof such as is shown in these photographs.

That's because the fishmouthing is occurring at the butt joints of the shingles where more moisture is passing out of the roof structure into the back side of the shingle above each butt joint.

You can thus determine the actual pattern in which the shingles were applied to the roof.

"Laddering," while permitted by some manufacturers and standards, is a less workmanlike shingle installation and may result in a localized early wear area on a roof. Ladder-pattern shingle application shows that the roofer liked to work up the roof from one position for as long as possible before moving.

Like cupped and curled asphalt shingles, fishmouthed shingles are also fragile and near end of life and are, as with ordinary cupping, damaged if walked-on.

In some other cases a defective product might cup or curl But we don't have authoritative data on the frequency of that defect. [Photo of fishmouthed shingles courtesy of Carl Gerosa, New Rochelle, NY.]

Workmanship: Fasteners/Nailing Problems, Wind Damage appeared to have led wind blow-off of these Atlas shingles, though an investigation of whether or not the shingles had self-sealed was also needed.

Workmanship: Fasteners/Nailing Problems lead to holes or wind blow-off

Workmanship: Fasteners/Nailing Problems lead to holes or wind blow-off. Notice that not only has one shingle already fallen or been blown off of the roof, but its neighbors are sliding down. Diagnosis from a photograph is questionable but there appears to be a nailing problem here.

Workmanship: Installation Pattern Problems:Laddering [Photo: Carl Gerosa, New Rochelle, NY.]

Workmanship: Flashing and underlayment problems
Workmanship: Improper materials/roof-slope problems
Holes and nail-pops in shingle roofs

In discussing wind damage to roofing with your insurance adjuster or roofing contractor, be sure to review the details of original and replacement shingle installation as this can give evidence about the underlying cause of roof failure as well as informing you of how to avoid roof shingle blow-off in the future.

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.

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.

Best Practices Guide to Residential Construction, by Steven Bliss. John Wiley & Sons, 2006. ISBN-10: 0471648361, ISBN-13: 978-0471648369, Hardcover: 320 pages, available from Amazon.com and also Wiley.com. See our book review of this publication.
Decks and Porches, the JLC Guide to, Best Practices for Outdoor Spaces, Steve Bliss (Editor), The Journal of Light Construction, Williston VT, 2010 ISBN 10: 1-928580-42-4, ISBN 13: 978-1-928580-42-3, available from Amazon.com
The Journal of Light Construction has generously given reprint permission to InspectAPedia.com for this article. All rights and contents are ©Journal of Light Construction and may not be reproduced in any form.
Architectural elements: the technological revolution: Galvanized iron roof plates and corrugated sheets; cast iron facades, columns, door and window caps, ... (American historical catalog collection), Diana S Waite, available used out of Amazon.
Green Roof Plants: A Resource and Planting Guide, Edmund C. Snodgrass, Lucie L. Snodgrass, Timber Press, Incorporated, 2006, ISBN-10: 0881927872, ISBN-13: 978-0881927870. The text covers moisture needs, heat tolerance, hardiness, bloom color, foliage characteristics, and height of 350 species and cultivars.
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
Handbook of Building Crafts in Conservation, Jack Bower, Ed., Van Nostrand Reinhold Company, NY 1981 ISBN 0-442-2135-3 Library of Congress Catalog Card Nr. 81-50643.
Historic Preservation Technology: A Primer, Robert A. Young, Wiley (March 21, 2008) ISBN-10: 0471788368 ISBN-13: 978-0471788362
Patio Roofs, how to build, Sunset Books
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
Slate Roofs, National Slate Association, 1926, reprinted 1977 by Vermont Structural Slate Co., Inc., Fair Haven, VT 05743, 802-265-4933/34. (We recommend this book if you can find it. It has gone in and out of print on occasion.)
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