Shingle cracks

16 year old roof (30 year shingles). Never seen “cracks” like this before. Causes? Concerns? Many of the shingles were cracked like this on the entire roof.

Any help is always appreciated.

BTW, would hate to be a roofer on a day like today. I think I lost 30 lbs. in the attic at today’s inspection. Of course it doesn’t help when you drop/lose your camera in 20+ inches of loose fiberglass insulation. After swimming/searching through the attic fiberglass pool for about 15 minutes, finally found it. Still scratchin’ my arms while I’m typing out report. Aint life grand.

Could be any number of things from thermal expansion / contraction, mineral fiberglass mat issues, asphalt coating… I suspect there is venting issues in the attic as well…ither way you should document same and recommend that further evaluation is warranted.



Thanks for replies. Now, how would you word it?

Without attic pics, I would guess ventillation problem. Were there baffles installed, or were there soffit vents at all, or were they blocked by insulation?

No venting concerns. The roof, overall, looked good and these cracks appeared to be “minor” ,but nonetheless, they’re still cracks. I just need some good reporting verbiage.

That’s called “craze cracking”, it’s not uncommon.

They’re cracks in the surface of the asphalt layer, common to many types of laminated comp shingles (and sometimes 3-tab) as they age. They don’t extend through the shingle and are not a defect, just a sign of aging.
They may start showing up at anywhere from about 12 years to 14 years give or take. It varies with the quality of the asphalt used to manufacture the shingle.

Over the years, the asphalt layer loses volatile oils and plasticizing compounds which dissapate to the atmosphere and/or are slowly leached by runoff.

This causes the asphalt layer to shrink and the surface tension created by the shrinkage is relieved by craze cracking.

Since the upper surface of the shingle is exposed to the elements, it shrinks the fastest.

The process may be hastened by poor venting, but it has more to do with asphalt quality.