360-724-8180 bradinspect@gmail.com

Most likely in the report this will be called staining, microbial growth, fungus, discoloration or a whole slew of other things including the dreaded M word.

This is a common condition found in many inspections that I conduct in the Pacific Northwest, especially in certain areas with little sunlight due to overhanging trees. It can range from light discoloration to full blown white and black.

The good news is: The attic is outside the building envelope, which is the physical separator between the conditioned and unconditioned environment. As an example, the air you breathe in your bedroom is inside the building envelope, the attic and crawlspace are outside the building envelope.

The bad news is: There is a moisture issue in your attic which could lead to structural deterioration of the roof decking (sheathing) and trusses/rafters, compromise your insulation from moisture (moisture compressing the blow-in insulation) as well as prematurely aging your roofing shingles from poor ventilation, Not to mention this staining will not go away on its own, even if you eliminate the source of moisture.


Let’s discuss the possible causes, many times it’s more than one issue.



  • Exhaust fans terminating into the attic and not to the exterior.
  • Blocked soffit vents (passive vents at the eaves)
  • Poorly sealed penetrations from inside the building envelope such as: attic hatches, light fixtures, smoke detectors, fan units etc.
  • Excessive long-term moss on the roof.
  • Inadequate ventilation
  • Water in the crawlspace
  • Roof leaks

How do I get rid of it?


Once the cause of the high moisture has been identified and corrected, we recommend remediation for many reasons.

  1. In order to confirm the conducive condition has indeed been corrected, periodic monitoring of the remediated area(s) should take place going forward.
  2. Depending on the severity of the staining there are many options to remediate or remove the staining.
  • Solutions such as RMR 86 do a decent job of taking the stained areas back to their original appearance.
  • A mold removal company, that will use techniques such as a biocide, Killz, dry ice blasting, wire brushing Hepa vacuuming, there are many options.
  • Replacement of the roof decking, something to consider if you plan on replacing the roof.
  1. Finally, as mentioned before, this staining will not go away on its own, consider this if you ever sell in the future, as it will most certainly be called out by an inspector at the next inspection.


In conclusion: This is a common condition found in the Pacific Northwest and found in one form or -another in approximately 75-80% of the attics we inspect. There are many companies out there that are in the business of Mold remediation, some good, some bad. If you are working with a realtor, huddle up and get a plan going forward and realize the next home will probably have some of the same, if not different issues.