?Causes of flashing buckling on new roof? 4

[EngineerofSteel]

I'm invited to look at a new roof, recently installed by a large, experienced contracting firm. For some unknown reason, the flashing is "buckling".

I have not seen this before. What are some of the potential causes?

pre-manufactured trusses, 24" o.c., 5:12 pitch, 40-foot span

We have had a lot of rain recently.

What should I look for during my site visit?

 

[bimr]

Asphalt shingles occasionally show buckles or ridges. This buckling is the result of the shingles being distorted due to movement of the roof deck on which they are applied.
Asphalt shingles have never been shown to buckle by
themselves.

Excellent article that discusses buckling:

http://www.rci-online.org/interface/2002-07-logan.pdf

http://www.pattoncontracting.com/roofing-buckling.htm

"Excessive attic moisture can also cause the roof framing and decking members to swell. Excessive swelling can buckle shingles,"

http://www.askthebuilder.com/B59_Asphalt_Roofing_Installation_Primer.shtml

Q: Why are my shingles doing the wave?

A:Buckling shingles can become humped or wavy, usually running in a straight line up, or across the roof.

Possible Causes:
Deck or felt movement often caused by varying moisture levels in the material under the shingles. The shift will cause the nails to move in accordance with the deck forcing the shingles closer or farther apart depending on the situation.

Improper nailing - nails will 'pop up' creating the buckling effect.

Shingles nailed too tightly together,

This decking (3/8") over 24" centers can be the cause due to clips, meant to hold the decking in place, coming lose or coming off.

Depending on the cause of the buckling, improving attic ventilation to eliminate excess humidity, removing fasteners and refastening or replacing distorted shingles can be some possible solutions.

http://roofrescueatlanta.com/faqs.html#ten