Newer roof with wet sheathing

This is a new one on me. A tear-off and replacement of fiberglass shingles was performed on this roof about 6 months ago. About 1/4 of the roof sheathing has mold growth on it and has about 60% moisture content. The roof has just a few pan vents and no soffit vents. The shingle installation looks good. Could the roof actually stay wet all that long since the venting is poor?

There could be a number of factors going on. Did they not put down felt? How wet was the OSB when they reinstalled the roof? It would be winter time so that might make a difference. If there is not enough air flow to properly dry out what may have been wet, it very well could “still” be wet.

Are there no gable end vents? If not, I can’t imagine that roof/attic is breathing the way it should be. Just imagine how that mold is going to explode once it warms up a bit. Did you happen to get any pics?


I would say ventilation is a big issue if they are no soffit vents. it would take a while to dry out if there is no air flow.

Did you check exhaust terminations and insulation to.?

Was it OSB or plywood? no soffit vents= no circulation

Everybody is right, inadequate ventilation, improper ducting and incomplete sealing of the penetrations from the living space and the heating ductwork could all easily contribute to condensation on the sheathing especially during the winter.

The ceilings by the outer walls have some mold on them too.
The roof was installed in late summer.
Just four pan vents on a 1400 ranch style home with a hip roof. No other venting present.
The humidity inside the occupied home is an unbelieveable 55%.
No ducting in attic.
R-13 insulation in attic.




There’s the culprit. Like previously mentioned, open penetrations in exterior walls and extreme moisture. With that low amount of insulation in attic, probably none in the the walls.

That roof sheathing by no means looks only six months old.

There’s culprit #1!

#2 would be NO AIRSEALING at the ceiling level.

#3 may be lack of good interior ventilation such as quiet, strong bath fans on timers and range hood vented to the outside .

Look for interior sources of moisture such as:

-Is the basement/cralwspace dry and is a moisture barrier at the ground/concrete floor level?
-Do they dry clothes inside as an energy saver?
-Is the dryer ducting leaking at joints?
-Any hobbies/other actions producing moisture?
-High #'s of plants?
-Large uncovered aquarium/s?

Once you take care of the above, the existing roof venting may be adequate!!!