Cracked roofing

[Ralph Smith]

Hi Folks, Can anybody explain this type of roof covering? The cracks and breaking of this reported 10yrs. old roof is the concern. I did commercial roofing for some years but the shingles I always laid were various forms of 3 tab. Also this is 2nd layer.
Ralph

[mthomas2]

Those appear to be "no-tab" dimensional shingles:

http://www.icc-es.org/reports/pdf_files/ICC-ES/1389.pdf

Did you get a look at the underside? My first thought is mechanical damage (was there a tree above this location?), impact damage from wind-blown material, or the result of someone dragging something across the roof.

[Ralph Smith]

Thanks for the info. The cracks are on all faces of the roof, they follow a diagonal, stepped pattern, and run from the bottom to the top, crack in every shingle in the line. One area of the garage roof has cracks 3" from the end of each shigle top to bottom. There is a 2nd layer underneath but the deck, as viewed from the attic, is in tip top shape. The cracks are everywhere!
Ralph

[rwand1]

I think its time to replace/budget for new shingles.

[Joseph Hagarty, CMI]

Originally Posted by rwand1

I think its time to replace/budget for new shingles.

Agreed

[mthomas2]

Now that I see the big picture, my previous theory is out the window, for sure.

[mnahrgang]

I wonder if the installers dropped the bundles and bent/damaged the corners and then installed them anyway. Now after ten years those "creases" have failed.

[rcramer]

It looks like a manufacture defect to me, it is way too uniform for it to be from mechinacal or installer defect. Being that it is only ten years old, they might be entitled to a rebate, if they are the origional owners of the roofing system. Just a suggestion.

[Ed Fako]

Possibly an OC or CT solid slab fiberglass light weight 20 year shingle.

The sealants they were using around that time period were too aggressive with their holding adhesion strength, which did not allow any movement for expansion and contraction. Hence, the uniform cracking throughout the roof.

Also, at least 2 different shinglers worked on the installation, and one installed them in the stair-step pattern and the other installed them in the "Racking" pattern.

Ed

[Kenton H. Shepard, CMI]

That's a type of thermal cracking. Shingles are splitting where they bridge the joints of underlying shingles.

As shingles cool, they contract, meaning they get smaller. As shingles get smaller, the joints between them grow larger, while the shingles bridging those joints gets smaller.

This condition creates stress in the bridging shingles above each joint and if the tensile strength of the adhesive strips exceeds the tensile strength of the shingles themselves, the shingles can split over joints in underlying shingles.

Since shingles are installed with subsequent courses offset six inches or so, the diagonal crack pattern across the roof is the clue.