what gives?

[ericwlewis]

does anyone know the cause of this??

This is a 5 year old roof with solid truss and osb structure below with adequate ventilation.

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[Chad Fabry]

Looks like they racked the shingles.

[mgbinspect]

Could it be a material defect? It seems that the shingle tabs have never properly sealed down. Shingle tabs don't easily release once they have sealed.

[Erby]

Shingles installed using the racking method.

Bends the corners every time. Too late to do much about it until it warms up. Then you can TRY sealing the corners down.

[utube]http://www.youtube.com/watch?v=z0_FYB0j2aI" type="application/x-shockwave-flash" wmode="transparent" width="425" height="344">

[Tom Raymond]

If they don't lift the tab to nail the loose end there is no curl. Problem solved.

[ericwlewis]

a little more info; I gently raised one of the tabs to find that the tar had in fact stuck and when this curl happened it pulled the wear layer off in the area of the last "dash of tar".

[mgbinspect]

a little more info; I gently raised one of the tabs to find that the tar had in fact stuck and when this curl happened it pulled the wear layer off in the area of the last "dash of tar".

Apparently, more stress is being applied to the single tabs than intended, which causes me to return to the suspicion of inadequate or improper fastening. The surface is moving more than it's supposed to?

[Marc]

I've done quite a few 3-tab shingle jobs, column by column, before but I measured very carefully and no problems resulted. It's hard to get it right. When it does go wrong, it looks just the photo in the OP.

Marc

[mgbinspect]

I've done quite a few 3-tab shingle jobs, column by column, before but I measured very carefully and no problems resulted. It's hard to get it right. When it does go wrong, it looks just the photo in the OP.

Marc

But, Mark (and Chad I guess), I am not grasping how that explains stresses able to separate the sealed tabs from the shingle below, well after installation. It seems there has to be some un-checked expansion and contraction going on - possibly exacerbated by the racking?

[ericwlewis]

last night I read as many sites Google brought up as possible.

-Certainteed has had many defective shingles around the time of this installation. I do not know the brand of these shingles.

-poor ventilation causes curling. This attic had cellulose blown in which I've found to be mostly DIY around here. I did not notice very many Styrofoam chutes coming from the soffits.

-rushed installation is a possibility. This was a production home.... I too have installed many a shingle, none to carefully at times, and never had this happen to any of mine. Would the result of racking show up years after the install?

The thing is that only one of the ends are curled (racking) but the "delaminated" end suggests defect. I don't think it's ventilation because the curling is limited to one end of most shingles [?]

I have given these possible scenarios to the client but would really like to know what gives.

signed, befuddled.

[Jim Katen]

There are lots of possible causes. Most that I can think of are related to poor installation. None of it matters right now. I'd tell them to hand-seal the lifting tabs with dime-sized dots of mastic and go on with their lives.

[mgbinspect]

There are lots of possible causes. Most that I can think of are related to poor installation. None of it matters right now. I'd tell them to hand-seal the lifting tabs with dime-sized dots of mastic and go on with their lives.

Translation: Alright everybody - break it up and go home.. []

[ericwlewis]

Thanks y'all