New roof raised in areas

[Trent Tarter]

Seen this yesterday on a new construction home. Not sure what would cause shingles to be raised slightly in straight lines?  

[John Kogel]

Are those ribs 4 feet apart, I think so.

OSB with swollen lips.

The stack sat out in the rain without a cover, and the edges all swelled up? I imagine that would do it.

[Marc]

Maybe its my imagination but mid-span of those two lines is a third one running at right angles to, and between, the first two.  John K's suggestion seems to fit.

I thought that newer OSB wasn't supposed to do that.

[inspector57]

The roofer likely did the building paper at the same time as the shingles and lapped the paper on top of the shingles on those raised rows.

[John Kogel]

2 hours ago, inspector57 said:

The roofer likely did the building paper at the same time as the shingles and lapped the paper on top of the shingles on those raised rows.

That is good practice, but doesn't leave a hump.

[John Kogel]

3 hours ago, Marc said:

Maybe its my imagination but mid-span of those two lines is a third one running at right angles to, and between, the first two.  John K's suggestion seems to fit.

I thought that newer OSB wasn't supposed to do that.

That's right, the edges are painted. Green means one thing, orange another. A look at sheathing seams in the attic might show something.

[John Ghent]

Could this perhaps be a modular home trucked to the site and assembled?  Hard to tell whats going on just with a roof shot.

[Trent Tarter]

10 minutes ago, John Ghent said:

Could this perhaps be a modular home trucked to the site and assembled?  Hard to tell whats going on just with a roof shot.

The home was built onsite, standard stick frame construction. Engineered truss roof structure with OSB sheathing.  

[Jim Katen]

Perhaps the OSB was soaking wet when the shingles went on. Afterwards, the OSB dried out and shrank, causing the buckling in the cover. 

[RK52]

The two prominent ridge /bulges are 9 rows apart. If you look to the right, another 9 rows down you can see a third ridge. Pretty uniform, though nothing 9 rows up.

I would expect to see quite a bit more perpendicular ridges too, if the OSB was soaked. Else all of it soaked along the long dimensions and not the short.

The ridges are smack in the middle line of the shingles, too....  I'm guessing something *weird* in the installation process, and not the weather.

[ejager]

I'm a little late to the discussion, but failure to leave spaces between the OSB sheets may result in buckling.

Panel spacing is an APA RECOMMENDATION, to provide installers with a means of minimizing the potential for panel buckling; however, it is not a requirement. Some manufacturers may require a space at the time of installation. Panel buckling may be an aesthetic or serviceability issue but is not a structural deficiency.

(http://www.apawood.org/buildertips/pages/M300.html)

[John Kogel]

It's not too late,  and thanks for the input.

They are correct to say that a gap is recommended. But as usual, they back down then and say it is not a structural deficiency. That is wrong. When OSB swells, it can pull the nail heads through the wood, or just pull apart around the nail. Add wind, and you got structure damage.

I'm just saying I wish the authority would speak up for best practices.