North Side Mold Inside Attic

I have this 2 story house with a walk up attic. Have mold collecting on the north side of the roof on the interior plywood decking. The front of the house faces north.

Have a very humid summer attic. Humidity collects and seems to evaporate on the southern side of the roof. Mold limits itself to the interior plywood on the northern side of the roof. Does not grow on the beams. Someone told me it had to do with the glue in plywood.

The southern plywood is clean. My theory is that the sun heats up the south roof and evaporates any moisture on the plywood.

Have a full ridge vent, vents at the east and west ends of the attic and soffits.

I would like to eliminate this and am even willing to replace the roof. Talked to several roofers about it and no one has a solution other than

  1. the venting must be wrong
  2. need to get an exhaust fan or dehumidifier

But no one has a suggestion on how to improve the venting since it seems complete. And I am not sure I want a mechanical dehumidifier solution in the attic that may prove noisy. Is there any alternative to plywoodthat will resist mold? I investigated metal roofs but it appears they need to be nailed to plywood. :expressionless:

where theres mold theres moisture.
so first make sure your not gettin moisture in thru your roof, on the side your talkin about.
if your roofs not leakin then you may have a condesation problem.
which is caused by a/c and heating problems in your attic.

good luck.


First ensure you have sufficient insulation and a good vapor barrier to reduce humidity from the house from entering the attic space. Make sure bathroom and kitchen vents are not venting to the attic space.

Are you sure it is mold?