What would cause shingles to crack like this? There are several shingles on this roof that is cracked in this manner. The owner states the roof is five years old. Gable and soffit vents only. One power roof fan.
Thanks
It is a little hard to see the cracks in the photo but check this info on manufacturer’s defects:
i can only make out 2 damaged, unless you have a lot more of this appearing after 5 yrs
my WAG would be damaged before or during installation
I agree with Bob
Who is Bob?
I meant Barry sorry Barry
Would he could be a Bob if his parents wanted lol
some fisherman you are
Bob keeps your hook, up 
LOLOL well we use dynamite here
Bad photo. Barry, there are several cracked shingles. Thanks!
Most houses out here, even with our heat, have only gable and soffit vents, if that. Like Bob said, installation. But how was the adhesion and granular holding up. Roofs fail sometimes…and sometimes long before they’re supposed to.
Bob who??
C’mon Carl, just playing off of Wayne’e earlier mishap.
And I am still waiting for the fish to bite! 
Uplift from high winds would be my guess. The shingle that’s ripped up the middle is directly above a seam in the row below. When the lower section flipped up it tore the layer above.
The shingles may be nailed too high, (installation flaw) or the tar adhesive strip isn’t working right (manufacture’s flaw). Or the weather’s been kind of extreme lately (global … bad weather :mrgreen:).
John Kogel
www.allsafehome.ca
Looks like installation problem. Heat usually does not cause cracks. It causes blisters and makes the granuals fall off. If it is a manufacture defect you will usually see it repeats on the run. And is in the same area of the strip. These are laminate shingles and have two layers glued together.
1 does it happen on more than one strip( being the 3 foot long shingle if american style and if metric than a little longer) Repeat
2 does it go thru both layers or just the top.
3 Is in in the same area of the strips if it repeats.
Was there only one layer of shingles, or was the new roof installed over an existing one? If so that could be part of the problem.
Wow. Very nice detective work Mark. Sounds easy now that you said it first.
I am
Have to use a float or a “Bob”.
I know that but you had not shown up yet!
BOBert :mrgreen: