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This document describes most of the factors which determine the life expectancy of an asphalt shingle roof - "roofing shingle wear factors".
These wear factors affect most asphalt roof shingle types, whether organic felt based or fiberglass fabric based, and whether
the shingle type is "cutout" or three-tab, strip-type, or a laminate-type roof shingle.
We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.
SHINGLE LIFE / WEAR FACTORS for Asphalt Shingle Roofing Products
This article is part of our series on inspecting, diagnosing, installing and repairing Asphalt Roof Shingles which tells readers how to identify & explain the most-common asphalt roof shingle failures.
[Click to enlarge any photo or image]
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.
While the historical cost-performance of this product has been good in most cases, durability issues and wear-out or material failures occur earlier than expected in some situations.
The expected life of a roof covering depends on many variables including:
Asphalt Shingle Quality: type, quality, thickness, shingle design (cutout 3-tab versus laminated) and rated or design-life of roofing material selected
Asphalt Shingle Color: in hot sunny climates lighter colors tend to resist sunlight damage and last longer. See ROOF COLOR RECOMMENDATIONS for details.
Roof Shingle Age: the shingles in the photo at the top of this page are organic based asphalt (asphalt-impregnated paper coated with mineral granules) at or near the end of their life.
Typical life expectancy for roofing products can vary widely as a function of the material composition, type, installation details, and other factors
discussed in depth at this website. Typical shingle life expectancies range from about 15 years to 40 years.
Roofing material storage conditions before & during installation can cause early roof failure and leaks and may also violate the roofing manufacturer's warranty.
Our photo at left shows water absorbed and soaked shingles taken from the middle of a pallet of asphalt roof shingles.
[Click to enlarge any image or photo].
At ROOF SHINGLE STORAGE we list the roof shingle storage conditions that affect the future life of the roof:
Building factors affecting asphalt shingle roof life:
Roof slope: On what degree of roof slope can asphalt shingles be installed? - According to the National Roofing Contractor's Association (NRCA) and the Asphalt Roofing Manufacturers' Association (ARMA) roofing guidelines, conventional roof shingles should not be used on slopes less than 3 in 12 - that is 3" of rise in 12" of run on a roof slope.
If asphalt roof shingles must be applied on such a low slope, say for aesthetic reasons, they're installed as a cosmetic applause on top of a nailable waterproof membrane, or laminated with courses of sealing membrane between every shingle course (costly and still a bit risky). We discuss roof slope in detail atASPHALT SHINGLE INSTALLATION
Roof problem areas due to roof shape & building design. Examples are complex roof shapes that make under-roof venting difficult or unfortunate architecture that places obstructions such as a wall or a chimney right in a roof valley, or causes other shapes which interfere with good roof drainage. (Shingles depend on slope and drainage to avoid roof leaks).
Sun exposure: orientation some roof slopes towards sunlight can cause faster wear on those slopes than on shaded roof slopes
Roof Ventilation: attic or under-roof ventilation. Un-vented roofs, especially in sunny hot climates, stay at a higher surface temperature and can be expected to have a shorter life. Roof ventilation is discussed in detail atROOF VENTILATION SPECIFICATIONS.
Technical material composition and asphalt shingle design details (roofing material components, manufacturing process, wind-uplift prevention). We compare types of asphalt shingles atASPHALT SHINGLE PROPERTIES
Marketing and economic considerations (aggressive sale of new roofing material by some contractors, reluctance to or economic reasonableness of patching damaged areas on older roofs)
Manufacturing Defects and Asphalt Shingles: even the best manufacturers are at risk of episodes of producing a defective product. The asphalt shingle
manufacturing line is a challenging environment where variations in control of the process can produce a defective product with a reduced life. The thermal
splitting failure discussed at this website is an example of a widespread fabrication defect that affected many asphalt shingle manufacturers. See
Mechanical-damage to roof shingles: mechanical damage to asphalt roofing results in granule loss, cuts, chips, pits, tears and can result from foot traffic, hail damage, wind damage, ice dam chopping, snow shoveling, falling tree limbs and a variety of other external means. Mechanical damage to shingles may require only spot repairs or it may be so extensive as to require complete roof replacement.
See MECHANICAL DAMAGE of SHINGLES
see HAIL DAMAGED SHINGLES
see WIND DAMAGE to ROOFS
Weather and Weather Exposure: variations in climate and other local weather conditions affect roof shingle life
Wind Effects on Roofing: exposure to damage (wind, tree limbs, hail, snow, ice, foot traffic).
Key in wind blow-off of asphalt shingles is whether or not the shingles were properly installed, especially properly nailed according to the manufacturer's recommendations.
Also on occasion a brand
new roof that has not had a chance for its self-sealing adhesive to work may blow off in windy conditions even if it was nailed properly. Review the workmanship defects below as a number of them constitute
improper nailing and can cause a wind failure of roofing that may otherwise may be misdiagnosed. Shingle wind damage details are
atWIND DAMAGE to ROOFS.
Nailing of Asphalt Shingles: asphalt shingle roof nailing errors: improper nailing pattern, omitted nails, too many nails, nails not properly placed
in the shingle, and lazy use of the roofing nailing gun: nailing without moving on the roof, leaning out too far, making nails
enter the shingle on an angle so that the nail head cuts the shingle; failure to set nails properly (too deep - cuts shingle,
too shallow, cuts shingle above).
The older roof nailing guns that used staples required even more careful use of that tool. If the
roof shingle staple was driven too deeply it cut the shingle and it would blow off of the roof. If the shingle was left too high
or canted (lazy-leaning out too far again) the protruding staple cut the overlapping shingle above. Shingle nailing details are
atASPHALT SHINGLE INSTALLATION Workmanship and roof failures are discussed
atWORKMANSHIP & ROOF DAMAGE
at LADDERING vs STAIR STEPPING SHINGLES
Underlayment Effects on Shingle Life: omitting the roofing underlayment (roofing felt or "tar paper" installed over the roof deck before shingles are applied), installing underlayment or shingles over a wet, icy, or snow-covered roof deck Roofing underlayment details are
atUNDERLAYMENT REQUIREMENTS on ROOFS
Roof Flashing Errors: there are too many of these to list on this asphalt shingle page. Water runs down hill. Flashing installers
sometimes forget that, misplacing flashing, omitting flashing, using continuous rather than step flashing at roof-wall abutments and
at chimneys, improper valley flashing, nails through flashing, relying on roof cement rather than flashing, and misplacement of drip
edge with its vertical section behind rather than over gutters.
OPINION: some roofers opine that underlayment is completely unnecessary.
I go with the manufacturer's recommendations. They have a high interest in the successful application of their product.
See these roof flashing articles:
Effects of Climate On Asphalt Shingles: Carl Cash asserts that the mean durability of
"20-year" shingles is less than 20 years everywhere in the U.S. except Alaska.
Variations in climate
permit calculation of a wear-acceleration factor for various cities. Higher
thermal load (hotter climates) means shorter life. Yuma, AZ mean durability
was calculated at 12.6 years, for example, and Ft. Meyer FL 14.1 years while
Chicago at 19.7 years and Erie, PA at 20.7 years showed longer life in cooler
Cost Effectiveness of Asphalt Shingles:
Other roofing materials also are affected by thermal loading. Cash calculates that the life cycle cost of
steep-slope roofing shows that asphalt shingles still provide the most economical performance for the home owner! ("Asphalt Shingle Performance," --
Given these variables, it is not likely that a "20-year" shingle will
expire exactly twenty years after it is installed. When a roof lasts longer
than its promised life no one complains. If a roof needs replacement
substantially sooner than its anticipated life, consumers are understandably
Asphalt Roof Shingle Wear Factors Research Citations
Also see key citations found at the end of this article at REFERENCES
Bailey, David M. Roofer: Steep Roofing Inventory Procedures and Inspection and Distress Manual for Asphalt Shingle Roofs. No. CERL-TR-99/100. CONSTRUCTION ENGINEERING RESEARCH LAB (ARMY) CHAMPAIGN IL, 1999.
Dunlop, Carson. Essentials of Home Inspection: Home Reference Book. Dearborn Real Estate, 2003.
Dunlop, Carson. Principles of Home Inspection: Roofing. Vol. 5. Dearborn Real Estate, 2003.
Dunlop, Carson. Principles of Home Inspection: Systems & standards. Review questions & answers. Vol. 15. Dearborn Trade Publishing, 2003.
Krivit, Dan, "Shingles, Recycling Tear-Off Asphalt. "Best Practices Guide."" [PDF] Construction Materials 21 (2007), Dan Krivit & Assoc., St. Paul MN, DKrivit@bitstream.net, Tel: 651-489-4990, Construction Materials Recycling Association (CMRA), Email: email@example.com, Tel: 630-585-7530, retrieved 8/8/2014, original source: https://www.shinglerecycling.org/sites/www.shinglerecycling.org/files/shingle_PDF/ShingleBPG%2010-07.pdf
Fry, Lloyd A. "Method of treating asphalt shingles and composition therefor." U.S. Patent 2,000,226, issued May 7, 1935.
Marshall, Timothy P., Richard F. Herzog, and Scott J. Morrison. "Hail Damage to Asphalt Roof Shingles." In 22nd Conference on Severe Local Storms. 2004.
Turos, Mugurel I., Augusto Cannone Falchetto, Gabriele Tebaldi, and Mihai O. Marasteanu. "The Flexural Strength of Asphalt Mixtures Using the Bending Beam Rheometer." In 7th RILEM International Conference on Cracking in Pavements, pp. 11-20. Springer Netherlands, 2012.
Taunton Press. Roofing. Taunton Press, 1997.
Verwimp, Jo, Marleen Rombouts, Eric Geerinckx, and Filip Motmans. "Applications of laser cladded WC-based wear resistant coatings." Physics procedia 12 (2011): 330-337.
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