Shingles shearing

[rlskfoster]

What could cause this type of damage. The shingles are torn at the same angle all over the roof. There was some foundation movement but not much more than typical for around here and it was only in one corner. The attic structure that I could see looked good with no pulled rafters and supported spans with purlins. The home has several vaulted ceiling ceilings so alot of the framing was not visible. The roof was bad and buyer is asking for a new one, but, I am curious about the cause.

Buster

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[Bill Kibbel]

Could it be the adhesive strip bonds too well and doesn't permit expansion without tearing the tabs?

I could be way off. I spend most of my time looking at slate and metal.

[Brian G]

Weird. The way they line up does suggest a larger movement, but how? How many lines were there like that?

Brian G.

Bumfuzzled [:-boggled

[DonTx]

The other shingles are curling at the corners. How old did the Sellers say it was?

Usually when I see a roof like this, it takes very little effort to pull them up.

My guess would be the foundation or some weird installation problem. What was the roof decking?

[Terence McCann]

A few years ago we had strong winds that lifted the shingles on my home in a diagonal fashion like that but it also took them off the roof and conveniently placed them in my backyard.

[rlskfoster]

The house was built in 1991 and I'm figuring the original roof.

The tears were for the most part in the same direction diagonally and it was like this over the entire roof. House was about 2000 sf under roof.

There was an active leak in two locations. We have been in a drought for a while but last weekend we got 3 inches of rain over 48 hours. The carpet was even wet in one location.

I was even wondering if the whole frame of the house could have twisted as the one corner dropped but I have seen a whole lot more movement than this house has and the roofs don't look like this one.

Oh well it may just be a head scratcher!

I advised a new roof and an Engineer to look at the one corner.

Thanks,

Buster

[Bob White]

This may be a goofy thought, but I' guessing that there's no underlayment -- That can do weird things to shingle as they attach themselves to the roof decking ---

[Tom Corrigan]

This is a common and warrantable defect in fiberglass matt roof shingles from 1985-1991. Further info is available at:

http://www.inspect-ny.com/welcome.htm#roofing

Tom Corrigan

[rlskfoster]

Tom,

This looks exactly like what has happened to the shingles in question. In fact, some of the pictures at the web-site could be swapped with my pictures and nobody would know the difference.

I have made my client aware and he is going to look into the situation.

I appreciate the response because I learned something new today. Thanks, Tom!

Buster

[mwg27]

Excellent post and link Tom...

Thanks

[Ken Melton]

I've seen plenty of roofs with vertical sheers through a number of courses, but your pictures do not reflect that. Your pictures look like diagonal sheers. It's almost as if the roof structure was exposed to a strong force (Wind?) at a gable end and the roof structure moved from end to end. The lower part of the roof structure would remain stationary as the ridge would move the most. Especially if supports were 24 on center and roofer was short on nails for sheathing. Sounds far fetched, but if the shingles were brittle enough (winter), I could invision this. Anyone setting off bombs in the neighborhood? LOL.

[mgbinspect]

A word to the wise, (from a previous disaster restoration contractor who had to figure this stuff out all the time to detirmine what was a "covered loss"), take the time to lift a few tabs. I'm reasonably confident that you will find that this roof is improperly fastened (either high, missing or overdriven fasteners) That eventually allows considerable stress to be applied to the sealed shingle tabs as the system at large expands and contracts with temperature changes. Do check for this along the cracked shingles!

I've seen systems that were only fastened by two instead of four nails! They were naturally cracked all to #@*.

It is far more likely that this is an attachment problem than a material problem.

Good luck!

[homnspector]

"Could it be the adhesive strip bonds too well and doesn't permit expansion without tearing the tabs?"

Thats the explanation I have heard from 2 different roofers. Basically a shingle defect, too much adhesion.

[Rob Amaral]

That is indeed the Corrigan shingle defect. He's right. The shadow profile confirms the relative age, the diagonal cracking is a classic evidence of the 'fiberglass mat shingle defect' very common in this type of shingle. Looks like multiple layers as well. May just be occurring at certain poorly-ventilated areas, like vaulted-ceiling areas.

"Tear-off/replace". Could start showing up at other areas. Very well documented problem. Absent other info in this inspector's post, this is what is looks like to me.

[Steve Boozer]

Great call Tom. I've seen this multiple times here in Ga. I did not read the link, but as soon as I saw Ricks pic, I knew what it was. It always appeared to be Genstar brand shingles that were the problem here. Then I think they became GS, then were bought out by Certianteed and then discontinued. I could always tell by the specific color down here, but the color in Ricks pic is not the color I'm used to.

[StevenT]

I know that fiberglass mat shingle is prone to cracking. But if that were the case, wouldn't the cracking be more "scattered" or over a larger area?

The cracking in the picture seems to be continuous and seems to have a point of origin and termination. Is this what fiberglass mat cracking looks like?

Is there a possibility that the sheathing is not properly attached or some other movement, maybe in conjunction with the fiberglass?

[Jim Katen]

Originally posted by StevenT

I know that fiberglass mat shingle is prone to cracking. But if that were the case, wouldn't the cracking be more "scattered" or over a larger area?

The cracking in the picture seems to be continuous and seems to have a point of origin and termination. Is this what fiberglass mat cracking looks like?

Is there a possibility that the sheathing is not properly attached or some other movement, maybe in conjunction with the fiberglass?

No, it's unlikely that it's related to sheathing movement. If it were, you'd see a pattern that resembled the 4x8 sheets of sheathing.

The diagonal pattern is typical of matt failure -- at least that's what I frequently see. If you look carefully, you can see that it follows the ends of each three-tab section as they stair-step up the roof. My guess is that once one tab tears, it relieves stress on itself, but then imposes stress on the one above or below it and the pattern of failure marches along. If my theory were correct, then I'd expect to see vertical tearing patterns on roofs that were installed using the racking method.

- Jim Katen, Oregon