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Five Daily
Registered User
Username: Kitchenista

Post Number: 12
Registered: 4-2002
Posted on Monday, May 13, 2002 - 9:26 am:   

Per Haag Engineering's "Asphalt Composition Shingle Roofing Pictorial" 5th ed.

"Horizontal cracks caused by thermal strains and in some instances by understrength of reinforcements, a manufacturing deficiency. This problem was not caused by wind effects." (2.1.10)

"Recall that each tab is fastened above by mechanical fasteners and below by self-sealing adhesive strips. Thermally induced strains have fractured the tab, seperating them from tops of the shingles at the line of least resistance." (2.1.9)

These paragraphs are describing pictures. (Sorry I can't post them up here... no scanner.) I think this book is a great resource for educating roofers who think blisters are caused by hail.

My take on if it is more prone to hail damage - I think it is as prone to damage as the side edge or butt edge of the shingle. I've seen roofs with thermal strains, but other wise the shingles are in good condition and no hail damage is found.

As for the "chips" you mentioned... have you noticed a difference between organic and fiberglass shingles? I THINK that the organic shingles will be less likely to demonstrate "shiny and black" then fiberglass. But on this point I am not sure. I haven't seen many organic roofs in my short time as an adjuster.

Jennifer (also in MN where I am not finding much damage just a lot of pushy roofers)
Steve Florig
Registered User
Username: Sflorig

Post Number: 5
Registered: 3-2001
Posted on Sunday, May 12, 2002 - 11:38 pm:   

Up here in Minnesota I am seeing a number of roofs that have comp shingles with thermal cracking.
Can I get a description of what exactly causes this? Is it strictly due to weather conditions? Is there any manufacturing defects involved? What effects will hail have on a roof that has thermal cracking? Will the roof be more prone to hail damage along the crack lines?
I find that it's often hard to tell whether the chipped off pieces of shingles are due to the long term effects of thermal cracking and were there prior to the hailstorm or whether they are from the hail hitting the cracks themselves. It's very hard to tell if these "chips" are fresh because when you scrape away some of the granuals on the shingles the underlying matting is often not shiny and black (usually an indication of fresh hail hits)
Any comments would be appreciated.

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