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ROOFING INSPECTION & REPAIR
AMERICAN CEMWOOD ROOFING
BEST ROOFING PRACTICES
BUILT UP ROOFS
CATHEDRAL CEILING VENTILATION
CERTIFICATIONS for ROOFING CONTRACTORS
CHIMNEY FLASHING Mistakes & Leaks
COLD WEATHER ROOF TROUBLE
DECKS, ROOFTOP CONSTRUCTION
EPDM, RUBBER, PVC ROOFING
EXTRACTIVE BLEEDING on SHINGLES
FIRE RETARDANT PLYWOOD
FLASHING on BUILDINGS
FLAT ROOF MOISTURE & CONDENSATION
Green House or Solarium Roof Leaks
HEAT TAPES & CABLES on Roofs for Ice Dams
ROOF ICE DAM LEAKS
MASONITE WOODRUF FIBERBOARD ROOFING
NOISE CONTROL for ROOFS
PLASTIC ROOFING TYPES
PVC, EPDM, RUBBER ROOFING
ROOF ARCHITECTURAL STYLES - PHOTO GUIDE
ROOF CLEANING RECOMMENDATIONS
ROOF COLOR RECOMMENDATIONS
ROOF DORMER TYPES - PHOTO GUIDE
ROOF INSPECTION SAFETY & LIMITS
ROOF JOB PROBLEMS, RESOLVING
ROOF LEAK DIAGNOSIS & REPAIR
ROOF NOISE TRANSMISSION
ROOF REPLACEMENT SNAFUs
ROOFING FELT UNDERLAYMENT REQUIREMENTS
ROOFING MATERIALS, Age, Types
ROOFING TILE SHAPES & PROFILES
ROOFING UNDERLAYMENT BEST PRACTICES
SADDLE CONSTRUCTION at CHIMNEYS
SNOW GUARDS & SNOW BRAKES
STANDARDS for ROOFING
STRESS SKIN INSULATED PANELS
TEST LABS - ROOF SHINGLE
TREES & SHRUBS, TRIM OFF BUILDING
TRUSSES, Floor & Roof
UNDERLAYMENT REQUIREMENTS on ROOFS
VENTILATION in BUILDINGS
WALK-ON ROOF SURFACES
WARRANTIES for ROOF SHINGLES
WORKMANSHIP & ROOF DAMAGE
Asphalt shingle cracks due to thermal splitting & defective product: this document tells readers how to identify & explain asphalt shingle cracking or thermal splitting, what causes shingle cracks or splits, and how to distinguish this product failure (which may be entitled to a warranty or class action claim) from other roofing product failures or defects.
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FIBERGLASS SHINGLE CRACKS - Thermal Splitting Asphalt Shingle Crack & Tear Failures Described & Explained
Fiberglass-based Asphalt Roof Shingle Cracking/Tearing/Splitting Failures
"Thermal splitting," or "cracking" which in fact is in most cases actually a tearing of the shingles is considered by experts to be the principal current problem with fiberglass-based shingles. We prefer the term tearing as a most accurate description of what's probably happening. Originally observed on the lightest-weight (15-year life) shingles this problem has now been found across all shingle styles, weights (life ratings), and we suspect, probably across most or all manufacturers of this type of product.
The thermal expansion of defective asphalt shingle product (common in the U.S. across many manufacturers in the early 1990's) followed by thermal contraction when cool weather approached, explained the tear shown in the shingle in our photograph just above.
See THERMAL EXPANSION of MATERIALS for a table of the coefficient of expansion of common building materials. We have not found a source defining the coefficient of thermal expansion of asphalt roof shingles - Contact Us if you can provide that information.
Does Thermal Splitting or Shingle Cracking Tearing Occur only in 3-Tab Asphalt Shingle Roofs?
No. Thermal splitting or tears occur in both conventional 3-tab shingles (photo above) and also in laminated asphalt shingle roofs.
Our photo (below-left) of thermal split/tear damage to a laminated asphalt shingle roof was provided by ASHI Home inspector Steve Mauer.
This unfortunate roof, inspected by Mr. Mauer in 2009, also suffered from granule loss (below-right) that in our OPINION looked like a defective product.
The same roof also included a damaged shingle that looked like a cracking and granule loss problem combined, but we think this was a shingle splice created at the factory during production - a bad individual shingle that is sometimes created when ends of shingle production substrate are spliced together. See SPLICE DEFECTS on ASPHALT SHINGLES
What Does Shingle Cracking or Shingle Splitting Look like?
Watch out: as we warn at ASPHALT SHINGLE FAILURE TYPES if conditions prevented the home inspector from direct access onto the roof or at least a look from a ladder set against the roof edge, shingle damage, cracks, and splits such as that shown in own photo (at left) could have been difficult or even impossible to spot. Inspecting the roof from the ground, even with good binoculars, can't show all roof damage types and conditions.
We have observed a variety of torn or split asphalt roof shingles, illustrated by our photographs below. (Click to enlarge any image.)
Horizontal Cracks & Splits in Asphalt Shingles
Both thermal splitting and other shingle cracks and splits can also occur in a horizontal pattern as we illustrate in our photographs below.
The horizontal cracking occurring in these fiberglass-based asphalt shingles resulted in complete loss of some of the shingles from the roof surface. The silicone caulk was placed by the owner during an attempt to "re-glue" the lost shingle tabs. But using our pen we pointed out additional horizontal cracks and tears developing in the next course of shingles just below. From a the ground the lost shingles looked like an isolated problem. An on-roof inspection told a different story.
Both horizontal and diagonal or vertical tearing may occur in the same roof as we illustrate in our photo at left (Click to enlarge).
What is the Cause of Thermal Splitting Cracks in Fiberglass-based Asphalt Roof Shingles?
Our photos above demonstrate two classic thermal split patterns in fiberglass based asphalt shingles: vertical splits running straight up the roof (above left) and diagnoal splits following butt joints (above right).
Normal Age & Wear Cracking in Organic Mat Asphalt Roof Shingles
Organic mat asphalt shingles also may show cracking and accompanying granule loss. Defective asphalt shingle products of either organic or fiberglass based shingles may experience several failures including cracking, tearing, granule loss, blistering, etc. So, splits or cracks can occur in both organic-mat based and fiberglass-mat based asphalt roof shingles.
But thermal splitting is particularly a problem with fiberglass mat based asphalt roof shingles.
Normal Asphalt Single Wear Cracking & Granule Loss
Our photos (left and below) show a badly worn organic mat asphalt roof shingle with multiple fine cracks throughout its surface. This shingle is worn-out, but the wear pattern is homogenous over the roof slope and in our opinion is a normal wear condition.
Hairline cracks appear in the (generally thicker) organic mat based asphalt roof shingles as a normal sign of aging, and normally late in the life of the roof shingles.
Our OPINION is that a variegated cracking in a somewhat random pattern over the exposed shingle surface is a common age and wear indicator found on older organic based (paper) substrate asphalt shingle roofs.
But catastrophic early shingle splitting failures like the ones illustrated earlier in this article were principally a problem of lightweight, fiberglass-mat based asphalt roof shingles made during the period discussed above. Roughly, from 1992 - 1997.
Cracking due to cold weather installation & bending ridge or hip cap shingles: see RIDGE & HIP CAP SHINGLES for additional discussion of distinguishing cracking wear failures from other types of shingle failures.
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.
Readers are also invited contribute roof failure information to the web author for research purposes. web author for research purposes.
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Frequently Asked Questions (FAQs) about cracked or broken roof shingles & thermal splitting: cause, effects, remedy, warranty
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