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This article discusses the key properties of asphalt roof shingles, compares organic and fiberglass matt shingles, lists and compares types of asphalt shingles: 3-tab, laminated, etc., and discusses shingle warranties, stains, wind resistance, and fire resistance. This article series discusses best practices in the selection and installation of residential roofing. This article includes excerpts or adaptations from Best Practices Guide to Residential Construction, by Steven Bliss, courtesy of Wiley & Sons. Green links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman. Properties & Types of Asphalt Roof ShinglesAdapted/paraphrased with permission from Best Practices Guide to Residential Construction, chapter on BEST ROOFING PRACTICES: Asphalt shingles, which cover 80 to 90% of residential roofs, have undergone much change in the last 20 to 30 years. Until the late 1970s, all asphalt shingles were manufactured from a heavy organic felt mat that had established a reputation for both strength and flexibility and generally outlasted their 15- to 20-year life expectancy. Since their introduction in the late 1970s, fiberglass shingles have come to dominate the market, accounting for over 90% of shingles sold today. However, premature failure of some fiberglass shingles in the 1980s and 1990s tarnished the product’s reputation and spawned a number of lawsuits and resulted in a toughening of standards and a general improvement in fiberglass shingle quality. Details about these fiberglass shingle problems are at CRACKS in FIBERGLASS SHINGLES.
Asphalt Roof Shingle QualityShingle quality is often difficult to determine visually since it is based largely on hidden factors such as the strength of the reinforcing mat (organic felt or fiberglass), the strength and flexibility of the asphalt, and the amount and type of fillers used. In most cases, however, the guidelines outlined below can help to select shingles that perform as promised. Organic Felt vs. Fiberglass Asphalt ShinglesOrganic shingles are built around a thick inner mat made from wood fibers or recycled paper saturated with soft asphalt. Fiberglass shingles, on the other hand, use a lightweight nonwoven fiberglass held together with phenolic resin. Both shingles are then coated on top with a layer of harder asphalt and fillers and topped with colored stone to create a decorative surface and protect against ultraviolet light. A thin layer of asphalt on the bottom is coated with a nonsticking dusting that keeps the shingles from sticking in the bundle. Each type has its pros and cons. Table 2-2 below compares the pros and cons of organic asphalt shingles (Standard ASTM D255) and fiberglass based asphalt shingles (Standard ASTM D3462).
Organic Asphalt Roof Shingles: CharacteristicsIn general, organic shingles have better tear resistance and resistance to nail pull-through than fiberglass shingles, making them less likely to blow away during a cold weather installation when they have not yet had a chance to seal.
Although uncommon, manufacturing defects that allow water penetration into the mat can lead to premature curling and cupping of organic shingles. Blistering (photo above left, for details see BLISTERS on ASPHALT SHINGLES) and curling (see CURLING ASPHALT SHINGLES) in warm climates has also been occasionally reported. Organic shingles cost more than comparable fiberglass shingles, but remain popular in colder regions and throughout Canada. With organic shingles, shingle weight tends to be a good predictor of performance and longevity since the added weight usually indicates a thicker mat saturated with more soft asphalt. Fiberglass Based Asphalt Roof Shingles: CharacteristicsFiberglass shingles, built on a thin nonwoven fiberglass core, were first introduced in the late 1970s and now account for over 90% of the shingles sold. Because they use less asphalt, they are lighter and generally less expensive than organic shingles. Because fiberglass mats are more fire-resistant and moisture-resistant than felt, most fiberglass shingles carry a Class A (severe exposure) fire rating and are less prone to cupping and curling from moisture damage.
After they have sealed, they can still tear from movement in the sheathing, since fiberglass shingles have little give, unlike organic shingles. In this situation, if the bond strength of the adhesive strip exceeds the tear strength on a lightweight shingle, the shingles can crack. Premature failure of some fiberglass shingles due to splitting or cracking led to a number of class-action lawsuits in the 1980s and 1990s. (Photo at left). The problems were primarily with lower-end shingles with lightweight mats, types that have been largely eliminated from the market. But it still pays to buy ASTM-rated products from a reputable company that provides a good warranty. Details about these fiberglass shingle problems are at CRACKS in FIBERGLASS SHINGLES. 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. Architectural Shingles - Laminated Asphalt Roof Shingles: Characteristics
Also called “architectural” or “dimensional” shingles, these have two layers laminated together at the lower half of the shingle, giving the roof a thicker textured appearance with deeper shadow lines. Our photo (above-right) is a GAF illustration of their Royal Sovereign® laminated asphalt roof shingle. Depending on the shape and size of the cutouts, half or more of the exposed shingle area is triple thickness and the rest double. With the added thickness and without the tabs, which typically wear out first in three-tab shingles, most laminated shingles carry longer warranties as well as higher wind ratings, some as high as 120 mph. While not immune to the problems of other shingles, such as premature cracking, it is reasonable to expect good performance from a reputable brand. One problem unique to laminated shingles is the loosening of the bottommost piece of the shingle caused, in part, by nailing above the line where the double thickness ends (Figure 2-1 above left). On many laminated shingles, nails must be precisely placed so they are high enough to stay hidden while still penetrating both layers. Wind Resistance of Asphalt Roof Shingles
Most shingles carry a windresistance rating of 60 miles per hour as tested under ASTM 3161 or UL 997, while specialty shingles may be rated to as much as 130 miles per hour. While laboratory tests may not predict actual performance in a storm, a higher rated shingle will likely perform better than a lower rated one. Shingles rated at over 100 mph are often special order items and typically require six rather than the usual four nails per shingle. Adding two extra nails and extra dabs of plastic roofing cement to a regular shingle can also increase its performance in high-wind conditions (see “Fastening (Nailing) Requirements for Asphalt Shingle Roofs” and “Manual Sealing Requirements for Asphalt Shingle Roofs” ). A wind-resistance rating is not the same as a warranty. Shingles that carry a wind-resistance warranty generally require that the shingle tabs have been adequately sealed to the adhesive strip and most limit wind coverage to five or ten years from installation. In cold, cloudy weather or on a steep north-facing slope, manual sealing with roofing cement may be necessary. Algae Resistance of Asphalt Roof Shingles
Some experts attribute the spread to the increased use of crushed limestone as a filler material in asphalt shingles. Limestone is economical and makes a durable shingle, but the calcium carbonate in the limestone supports algae growth. In algae-resistant (AR) shingles, zinc or copper granules are mixed in with the colored stone topping. When the shingles get wet, the zinc or copper is released, inhibiting algae growth. Warranties for algae resistance are usually for less than 10 years since the protection ends when the mineral washes away. Some shingles have longer lasting protection than others due to a higher percentage of AR granules. Details about algae stains and other stains found on roofs are at the following articles: STAIN DIAGNOSIS on ROOFS ROOFING INSPECTION & REPAIR Definitions of Fire Ratings for Asphalt Shingle & Other Roofing MaterialsDetails about roof fire ratings and details about the applicable standards are at FIRE RATINGS for ROOF SURFACES. Excerpts are below. Fire ratings for roof coverings describe how well the roof covering resists fires including the ability of the roof to resist catching fire from a lightning strike, if a spark or ember lands on it (say from a nearby chimney or from a forest fire), as well as the resistance to fire spread if the material is ignited. Keep in mind that the purposes of roof covering fire ratings (to describe the fire resistance of a roofing material), and the intent of roof fire resistance in general are to allow building occupants more time to escape in event of a fire, not to guarantee that the building nor its occupants will be unharmed in the event of a fire. A table of roof fire ratings and details about the applicable standards is at FIRE RATINGS for ROOF SURFACES.
All roofing materials that carry any fire rating (A, B, or C) must:
The U.S. Federal Housing Administration (FHA) and other lenders require that building roofing materials conform to these standards. Various U.S. national or model building codes & state & Canadian Provincial building codes or fire codes require that roofs must carry at least a Class C fire rating or better. Watch out: if a roofing shingle or other roof covering material is not installed exactly according to the manufacturer's recommendations its fire rating may be compromised and reduced, as may the roof warranty too. Also, a roof that has resisted a fire successfully, and thus helped protect the building from a fire, is likely to need to be replaced after a fire or after exposure to high heat from a nearby fire. Also watch for discount-grade roof shingles that may carry no fire rating whatsoever. Also see these roofing material articles where we describe fire ratings:
Readers should also see ASPHALT SHINGLE FAILURE TYPES and Environmental Issues - Asbestos Roofing/Siding as well as SLATE ROOF DURABILITY and STAIN DIAGNOSIS on ROOFS, WARRANTIES for ROOF SHINGLES and WOOD SHAKE & SHINGLE ROOFING and finally WORKMANSHIP & WIND DAMAGE. For roofing material testing services and shingle testing see TEST LABS - ROOF SHINGLE. - above section added DF. Continuing from from Best Practices Guide to Residential Construction: Three Key Manufacturing Standards for Asphalt Roof Shingles: ASTM D-3462, ASTM D-225, ASTM D-3018In the past, most companies did their own testing, but under pressure from contractors’ associations and others, most now use independent certifiers such as UL. Note: See our complete list of roofing standards found at STANDARDS for ROOFING - there are a lot of them. ASTM D3462 - Fiberglass shinglesASTM D3462 - Fiberglass shingles are covered by ASTM D3462, which includes a tear test as well as a new nail-pull-through test added after fiberglass shingle failures started occurring in the late 1980s.
A new pliability test was also added in recent years. With fiberglass shingles, look for the UL label next to the ASTM D3462 certification. This is not the same as a UL listing for a fire rating, which is printed on most fiberglass shingle packages. More and more jurisdictions are requiring compliance with ASTM standards, but discount shingles are still available with no certification. As with many consensus standards, the ASTM D3462 requirement for tear strength of fiberglass shingles is considered by many experts to be a bare minimum rather than a guarantee of high quality. Also, once installed the shingles’ strength will likely diminish. So finding products that exceed the minimum is recommended for demanding applications. ASTM D225 - 07 Organic Felt Asphalt ShinglesOrganic asphalt shingles are covered under their own standard, ASTM D255 ASTM D225 - 07 Standard Specification for Asphalt Shingles (Organic Felt) Surfaced With Mineral Granules
Related ASTM Roofing Standards: D1079 - Terminology Relating to Roofing and Waterproofing [ASTM D255-92 referred to in the original text, Standard Method for Steam Distillation of Bituminous Protective Coatings was superceded and was withdrawn in 2000. See ASTM D225 discussed above - Ed]. ASTM D 3018 - Class A Asphalt Shingles Surfaced with Mineral GranulesASTM D3018 / D3018M - 10a Standard Specification for Class A Asphalt Shingles Surfaced with Mineral Granules
Warranties for Asphalt Roof ShinglesShingle warranties run from 20 to over 50 years. Although products with longer warranties are usually of higher quality, in some cases, the longer warranties are more of a marketing strategy than an accurate predictor of shingle life. While the specific terms of the warranty are important, more important is the manufacturer’s reputation for warranty service in the local area. All manufacturers retain the right to void the warranty if installation instructions are not closely followed, and they can often find a way to avoid honoring a claim if so inclined. Key issues to consider in a warranty are as follows:
Details about roof shingle warranties are at WALK-ON ROOF SURFACES -- Adapted with permission from Best Practices Guide to Residential Construction. Resources: Roofing Materials & Equipment SuppliersManufacturersAsphalt ShinglesAtlas Roofing Corp. www.atlasroofing.com Fiberglass and organic felt shingles Certainteed Roofing www.certainteed.com Fiberglass shingles Elk Premium Building Products www.elkcorp.com Fiberglass shingles GAF Materials Corp. www.gaf.com Fiberglass shingles Georgia-Pacific Corp. www.gp.com/build Fiberglass and organic felt shingles IKO www.iko.com Fiberglass and organic felt shingles Owens Corning www.owenscorning.com Fiberglass shingles Tamko Roofing Products www.tamko.com Fiberglass and organic felt shingles Low-Slope Roofing MembranesDuradek www.duradek.com Vinyl roofing and walkable deck membrane Firestone www.firestonebpe.com RubberGard EPDM residential roofing system GenFlex Roofing Systems www.genflex.com Peel-and-stick TPO membrane Hyload, Inc. www.hyload.com Kwik-Ply self-adhering polyester and coal-tar roofing membrane Ridge VentsAir Vent/A Gibraltar Company www.airvent.com A complete line of roof ventilation products, including shingle-over and exposed-ridge vents with exterior wind baffles and internal weather filters. Also soffit and drip edge vents and passive and powered attic turbine-type vents. Benjamin Obdyke www.benjaminobdyke.com Shingle-over ridge vents. Low-profile Roll Vent uses nylonmatrix. Extractor vent is molded polypropylene with internal and external baffles. Cor-A-Vent www.cor-a-vent.com Shingle-over low-profile ridge vents, including Cor-a-vent, Fold-a-vent, and X-5 ridge vent, designed for extreme weather. Corrugated core. GAF Materials Corp. www.gaf.com Cobra vent: roll-out shingle-over ridge vent with a polyester-matrix core 102 CHAPTER 2 | Roofing Mid-America Building Products www.midamericabuilding.com Ridge Master and Hip Master shingle-over molded plastic ridge vents with internal baffles and foam filter Owens Corning www.owenscorning.com VentSure corrugated polypropylene ridge vents; also passive roof vents and soffit vents Trimline Building Products www.trimline-products.com Shingle-over low-profile ridge vents, Flow-Thru battens for tile roofs Elk Premium Building Products www.elkcorp.com Highpoint polypropylene shingle-over ridge vents Tamko Roofing Products www.tamko.com Shingle-over ridge matrix–type Roll Vent and Rapid Ridge (nail gun version) and Coolridge, which is molded polypropylene with external and internal baffles Venting UnderlaymentsBenjamin Obdyke www.benjaminobdyke.com Cedar Breather, a 3/8 -in.-thick matrix-type underlayment designed to provide ventilation and drainage space under wood roofing More Information about Roofing Materials, Methods, StandardsAsphalt Roofing Manufacturers Association (ARMA) www.asphaltroofing.org Cedar Shake and Shingle Bureau www.cedarbureau.org Metal Roofing Alliance www.metalroofing.com Tile Roofing Institute www.tileroofing.org ####### -- Adapted with permission from Best Practices Guide to Residential Construction. Frequently Asked Questions (FAQs)... Ask a Question or Search InspectApediaUse the search box below to ask a question or to search the InspectApedia.com website. Ask a Question or Enter Search Terms in the InspectApedia search box just below. Technical Reviewers & ReferencesRelated Topics, found near the top of this page suggest articles closely related to this one.
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