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Causes of Wear or Leaks in Asphalt Roofs
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• Causes of roof shingle wear and failure

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.

This document is a chapter of Asphalt Shingles Home Page: which tells readers how to identify & explain the most-common asphalt roof shingle failures. 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. © Copyright 2009 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

SHINGLE LIFE / WEAR FACTORS for Asphalt Shingle Roofing Products

• 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.
  
  
• 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
  
  
• Sunlight and Heat Effects on Asphalt Shingles: Storing shingles in hot sun makes them stick together, making damage likely as they are pulled out of their bundle.
  
  
• Cold and Freezing Effects on Asphalt Shingles: Storing shingles in freezing conditions increases the chances that a shingle will crack when being used if applied in cold weather, especially ridge cap shingles which break when bent. We used to cut those and then leave them inside on a radiator until needed.
  
  
• Rain Effects on Asphalt Shingles: believe it or not, shingles are not quite waterproof and depend on roof slope to shed water effectively. Shingles that are left exposed to rain and then installed may violate the manufacturer's warranty and may fail early, possibly due to the effects of temporarily trapped moisture at the time of application. We have found sections of asphalt shingle roofs all showing early wear traceable to a specific bundles of asphalt shingles that were at the top of the stack and exposed to the weather. This photo shows the effects of rain on shingles when the bundles were left outside for some time before use.
  
  
• Stacking Shingles in Storage: shingles should not be stored at the supplier nor at the job site stacked higher than two pallets. If shingles need to be stacked higher, separator boards or plywood are needed under each pallet to protect the shingles below from damage by the weight and edges of the pallet and shingles stacked above. We've seen shingle pallets eight-high with no inter-pallet protection at HG Page Lumber in Poughkeepsie and at an occasional Home Depot. But don't try giving the supplier your personal advice about how to stack their product, you'll just annoy them. Inspect and reject visibly damaged shingle bundles and hope that there are not more subtle damage effects not visible at first sight.
  
  
• Bending Asphalt Shingle Bundles: roofers like the shingle bundles to get up on the roof by magic - by a special loader or carried up by an assistant. A smart assistant spreads the bundles out over the roof to avoid too much weight in one place (point-load structural failures). But especially on a steep pitch roof, some "experts" put all of the bundles of shingles across the ridge. Bending shingles over the ridge, especially in cold weather, may violate the manufacturer's warranty and may damage the shingles, including subtle damage that appears after installation as early cracks, tears, or failures. Reference: http://www.owenscorning.com/around/roofing/specs/Classic-C.pdf from Owens Corning cites their requirements for handling and storing shingles.
  
  
• Asphalt shingles should be stored: flat, in un-opened bundles with labels intact and legible, in cool, not freezing and not hot temperatures (under 110 degF.), under cover, protected from the weather, protected from damage by stacking more than two pallets high, and kept that way until they are ready for use.
  
  
• Asphalt roof shingles should be delivered: in flat, un-damaged, un-opened bundles, protected at the job-site (as described above), and when moved to the rooftop, shingle bundles should be laid flat, not over the ridge, and should not be placed with too much weight in locations that may damage the building structure.

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).
  
  
• 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.
  
  
• Technical material composition and asphalt shingle design details (roofing material components, manufacturing process, wind-uplift prevention)
  
  
• 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.
  
• 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.
  
  
• Roof Installation Workmanship: installation/workmanship details such as the following:
• 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.
  
  
• 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
  
  
• 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.

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 climates.

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," -- Carl Cash.)

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 concerned.

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Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

ROOFING INSPECTION & REPAIR
ASBESTOS CEMENT ROOFING
CERTIFICATIONS for ROOFING CONTRACTORS
CHOOSING A ROOFING CONTRACTOR
ASPHALT ROOF SHINGLES
  SHINGLE LIFE / WEAR FACTORS
  ASPHALT SHINGLE FAILURE TYPES
  ALGAE, FUNGUS, LICHENS, MOSS on SHINGLES
  BLACK STAIN REMOVAL & PREVENTION
  BLISTERS on ASPHALT SHINGLES
  CRACKS in FIBERGLASS SHINGLES
  CUPPING ASPHALT SHINGLES
  CURLING ASPHALT SHINGLES
  FISHMOUTHING ASPHALT SHINGLES
  GRANULE LOSS from SHINGLES
  HAIL DAMAGED SHINGLES
  LADDERING & STAIR STEPPING SHINGLES
  MOSS & LICHENS on SHINGLES
  ORGANIC FELT SHINGLE DEFECTS
  SPLICE DEFECTS on ASPHALT SHINGLES
  STAINS on ROOF SHINGLES
  WHAT ARE ASPHALT SHINGLES
FIRE RETARDANT PLYWOOD
ROOF INSPECTION SAFETY & LIMITS
ROOF VENTILATION SPECIFICATIONS
ROOF VENTING ENERGY SAVING DETAILS
SLATE ROOF INSPECTION & REPAIR
  SLATE ROOF PHOTO LIBRARY
  SLATE ROOF INSPECTION CLASS
SOD ROOFING
SIDING WOOD
STAIN DIAGNOSIS on Building Exteriors
STAIN DIAGNOSIS on Roofs
STANDARDS for ROOFING
STONE ROOFING
THATCH ROOFING
THERMAL EXPANSION of MATERIALS
THERMAL MASS in BUILDINGS
THERMAL MASS in UPSTAIRS
TILE ROOFING
WARRANTIES for ROOF SHINGLES
  SHINGLE CLASS ACTION
  REPORTING SHINGLE FAILURES
  ROOF FAILURE REPORT FORM
WORKMANSHIP & WIND DAMAGE

• 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 Cash, P.E., Construction Business and Technology Conference, Providence Rhode Island, 2/28/97

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