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Hi. I have two questions regarding oil canning:
1) Is it common or normal for oil canning to bend a metal roof seam?
2) It is common or normal for oil canning deformation to be continuous across multiple panels?
The roof in questions is Snaplock 550 1.5" Standing Seam. It's 24 gauge galvalume steel with striations. It was just installed about 6 weeks ago on a new construction in South Florida. When installed, it had no bulges or oil canning. Recently, we had our first cold front of the season and it developed a continuous bulge that spanned about 9 panels and the bulging affected the seam.
I've reached out to the installer and his initial response was the decking. This didn't make sense to me as this was not present when the roof was first installed. The roofer then climbed up on the roof and was able to push the bulge in. He then changed the reason to oil canning.
To me, oil canning makes sense if the occurrence was within one panel or in random places across adjacent panels. The fact that the bulge is continuous across 9 panels makes me believe that this may be an installation issue.
I purposely selected a clip system so that the metal panels would be able to expand freely. In my opinion, the affected panels cannot expand resulting in the bulging.
One last thing to add, is that when the panels were formed on site, about 20% of the panels were formed incorrectly at the seam. The snap-lock feature was too small preventing panels to lock together properly. The panel supplier replaced several panels without issue. However, I am concerned that the affected panels were produced incorrectly and resulted in tighter than normal snap-lock feature which prevents thermal movement of the panels.
Is this something that I should take to an independent roof inspector? I greatly appreciate your help. Thank you.
Thank you. I also received the photos you sent me. Sometimes photos can have optical illusions but it looks to me like the decking is not flat. The ripples you describe are typical of when panels are installed over an uneven deck. There probably is some chance the panels are too tight against the ridge or are not allowing enough elongation at the eave but my gut tells me the deck is uneven. Why was it not immediately apparent? I really don't have any explanation for that unless perhaps the panels were installed when it was very cold but even that is not a good explanation. Can you tell from inside the building if the roof deck is uneven or the trusses have sagged or something?
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