Buckling wavy roof


Home built in 1991. CertainTeed Integrity Roof System installed 3 months ago after tear off & removal of old asphalt shingles. Attic foam insulated. Removed old attic ventilation fan that was no longer in use and installed ridge vents. Comments?


Looks like the sheeting is telegraphing through the shingles. It could be caused by the roofers causing it to become loose and not nailing it down or could have been installed too tight from the start and caused a bit of buckling.


If the sheeting isn’t loose then I’d say those humps were there before the roofer ever touched the roof. And that’s one of those things that goes 90% unnoticed by homeowners, its rare for them to pay much attention until they get their roof replaced. So as a roofer when I’m working on a house with any deficiencies (cosmetic), I always take before pics so they can’t claim it wasn’t there before.


As island said, from the pictures my best guess would be a sheathing issue. Possibly sheathing not nailed properly, loosened during tear off and not rescued, or possibly pushed up by the foam insulation. Normally sheathing can be inspected from the attic, but if the roof deck is sprayed with foam you will need to have a roofer pull some shingles to investigate.

Have you talked with your roofer and had them look at the roof?


It’s some sort of picture framing. Was the foam system installed before the roof, or after? In South Texas the foam applicators want a fully closed system without ventilation. Your home has ridgevent, so I would think that is eliminating pressure building up. Those humps look pretty large. I’m agreeing. I’d pull a few shingles off and you will find the answer real quick.


The open cell foam insulation has been on the attic ceiling for at least 10 years. Prior to the new roof, there was an old unused attic fan on the back of the roof (not on the side that has the buckling) that left unsightly rust stains on the roof. The old unused rusty fan was removed and the installers replaced the plywood that had a hole for the fan with a new piece of solid plywood. There is a tiny air space through the open cell spray foam insulation that led to the fan where the wire used to be that powered the fan once upon a time. Then, ridge vents were installed for the first time with the new roof.

Also, the buckling is barley noticeable on a cool cloudy day, but as soon as we have full sun, the waviness is immediately noticeable.



The BLUE = ATTIC location
YELLOW = where the shingles are buckling
The black dot within the blue square (attic) is the old unused attic fan that was removed during take off and install of new roof.


Just to make sure I am understating you correctly, is the bottom side of the roof deck spray foamed, or the ceiling of the living space foamed?

Looking at your picture, those short sections of ridge vent on a hipped house like yours are not providing much ventilation.


The attic ceiling is spray foamed… so the bottom side of the roof deck. The open cell foam insulation hides the rafters.


There’e your problem. every single roof we’ve done that had foam (panels or spray) directly against the roof deck has had serious moisture issues from sweating.


Foam has been there for at least 10 years and the previous roof did not have these issues.

Also, ridge vents were installed with the new roof without cutting through the foam.


Be honest, how closely did you pay attention to your roof before you had it replaced? I wish I had a dollar every time a homeowner told me that “it was never like that before” even after I pointed it out before I touched the roof. That’s why I take pics.


Your ridgevent isn’t doing anything.


In my area people have been doing this to the 100 yr old houses.

Even with the foam IMO you still need an air channel for ventilation.


The soaked and soft sheathing has pulled away from the nails. I’d bet it’s OSB which will move a lot with changes in humidity. I know of houses where depending on the temp/humidity the OSB will sag between rafters or lay flat. Hate to say this but you are looking at a complete re-sheet job to fix this, and the foam is going to come off with the sheathing.


The last person that touches it wears it.
A roofer either knows what he’s about, or he doesn’t, in which case he’s about to pay for the lesson.
You never touch a problem roof without discussing, and formally agreeing (in writing) with the owner, as to what the state the roof is in and advising on cost estimates.
Business is a bitch and you’ll find yourself in deep merda if you don’t stick to fundamentals