Cracked defective shingles

[Neal Lewis]

I don't know if i've ever heard of a definitive cause for cracks in older fiberglass shingles? Why do they crack in a straight line and not just random?

This line of cracks runs through seven courses of shingles, and is a second layer over older board sheathing.

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[gtblum]

I'd guess something under it must have moved. Any broken rafters in the attic? Any chance a tree or a limb came down on it?

[inspector57]

I can't tell much from the photo, but I have seen damage like that from foundation movement. My guess is something structural.

[Bill Kibbel]

It's a tear, not a crack. Was it just one, or were there other spots on this roof?

[Neal Lewis]

Yeah, you're right. They're torn, not cracked, and there are sections like this throughout. No problem with the structure at all.

I see this frequently with older fiberglass strip shingles and with architectural shingles from the 80's. There was the class action lawsuit with GAF Timberline.

But why the heck does it happen, especially in rows?

[Richard Saunders]

Excessive adhesive under the tabs from what I understand.

[Bill Kibbel]

After hurricane Hugo in '89, under pressure from the insurance industry, several shingle manufacturers increased the bonding strength of the tab adhesive. With normal expansion and contraction, the shingle mats perform like a single membrane and large tears form.

When many of the tears are vertical, across several courses, it usually indicates the shingles were installed with the vertical joints laddered rather than staggered up the roof.

Also, many three tab shingles back then had very thin mats, that wouldn't meet current tear-resistance requirements.

[Brandon Whitmore]

I would have guessed instability in the board sheathing as it expands and contractors more than plywood/ OSB and runs perpendicular to the cracks. I learned something new today.

Thanks.

[Chad Fabry]

It's always been my theory that they glued together too effectively and as the glue lost its resiliency the shingles tore in high stress areas. Whenever I see these tears the roofs are melded together like liberals at a Jesse Jackson rally.

On a hot day the shingles are baking and then a rain contracts the top layers while the 170 degree attic heats the bottom layers creating a differential expansion like a head gasket between an iron block and an aluminum head.

Please, consider the source.

[Jim Morrison]

Methinks Mr. Fabry has been working too hard lately.

Chad, why don't you plan a trip to Boston soon? You need some R&R. (no Jackson rallies, I promise)

[Jim Katen]

This is sometimes caused by zombies trying to claw their way into a house from above.

Jim Katen, Oregon

[Jerry Simon]

This is sometimes caused by zombies trying to claw their way into a house from above.

Jim Katen, Oregon

Must be one divine bottle of Scotch...

[Bain]

This is sometimes caused by zombies trying to claw their way into a house from above.

Jim Katen, Oregon

Must be a regional thing. Around here, the zombies typically hurl themselves at doors and windows. I don't think I've ever seen a zombie on a roof.