Improper insulation causes roof sheathing damage.

Its always good to actualy see the results of poor work. This home was only a few years old and the plumbing vent was inside the small attic space.
I noted unusual wavyness on the roof, but it was too steep to walk. SO instead I pulled down a little insulation.
No air gap for ventilation because they installed it wrong, and the whole area was covered in mold. The osb was also starting to delam. Suprising enough it was not damp, but must have been at times. My foot might have gone thru if I could have walked on the roof.
I guess it goes to show you what can happen to cathedral ceilings if they can’t breath.

Sean, just to make sure I understand what happened here, no vent baffle was installed between insulation and roof deck, blocking the soffit vent. Plumbing vent terminating in attic and put it all together and you get this mess.

Looks like you went beyond SOP and pulled the insulation down to get the visual you needed. :wink:

Good pics, Thanks

You are correct. If the whole roof is this bad I just saved the buyer thousands of dollars by going beyond the sop.
THe houses on either side of me had the same noticable roof wavyness.
All rental cabins.

Good find, just another example of fine unsupervised workmanship. No building inspector in that area till a couple of years ago.

Correct the 2 much larger flaws in your pictures, the continuous moisture source of the open vent and the cathredral ceiling insulation with NO ATTEMPT AT AN AIR BARRIER, and the moisture problems on the sheahing will disappear. Adding ventilation to this setup after correcting the vent situation will increase energy costs!!

They make baffle vents for that very purpose.They work great.I see more and more of what you are showing me and home owners screening at high energy bills.They do not realize there roof is degrading.Once the problem is solved it a much lower energy cost and a dryer environment.
No gabble end vents?

No gable vents. No room with the style of ceiling

Sorry Sean.I understand Sorry I did not read you where in small attic space I just surmised by the pics it was gambrel. . I assumed,Man I walked into that one.Any vents at all to release the moisture?

  1. A plumbing vent should terminate at the exterior to prevent sewer gas from entering the living space, not because it’s a big source of moisture.

  2. That’s an attic space, not a cathedral ceiling. The insulation should be installed in the floor, not between the rafters and the attic space vented to help keep the roof cooler… Basically, with no attic venting and insulation installed between rafters, the attic is part of the conditioned space and should have a minimum of 3.5 air changes per hour, just like the rest of the living space, to prevent moisture levels from becoming too high.

  3. In cathedral ceilings, the air space created by the baffles is to cool the roof and help prevent premature failure of the roof-covering material, especially comp shingles, due to excessively high temperatures. Moisture is a separate issue.

  4. Heat wouldn’t make OSB delaminate, but moisture would. The source of moisture should be found and corrected.

I agree. The insulation on the sheathing is improper. They’ve created an “unventilated attic”. The IRC addresses unventilated attics and this one is definitely wrong. The insulation on the roof sheathing is supposed to be closed cell foam and there should be no insulation on the ceiling, if that’s what they were trying to do. FUBAR.

I’m leery of the closed cell foam on the underside of the roof sheathing.
If the roof leaks, how will the occupant know? The leakage won’t be able to get past the foam and will be absorbed by the roof sheathing, which will decay quickly if it can’t dry to the inside and dries only slowly to the outside.
Also, heat will dissipate more slowly, since the roof can’t dump heat to the attic. This may cause comp shingles and underlayment to fail prematurely.

I’m with you 100%, but that’s what it says.

Yep, certain factions of the green building movement have been promoting it. Great ideas aren’t always great ideas.

Thank you Ken. I was totally confused by the pic,s. They are not explaining as to what is being described to how the roof would look as a cathedral ceiling.I should have pointed this out to hm in the first place.
Thank you for your observations.
You are right in all your observations and conclusions.