Thread: black flakes on sheathing

I have read through the black mold discussions and looked at the photos but I have not seen any photo like this one. This substance is flaking off. Could this be mold? It is located on the north side only.
I appreciate your comments.

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Originally Posted by Chris Hart

I have read through the black mold discussions and looked at the photos but I have not seen any photo like this one. This substance is flaking off. Could this be mold? It is located on the north side only.
I appreciate your comments.

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Any Smoke Smell?
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No smoke smell and the consistency of the flakes are not like ash like. There is no charring and it is only isolated on the north side. Also the trusses are not effected. I have seen a few fires in previous inspections and I don't think that is the cause.

The nails are rusted and the plywood is delaminated on the surface. There is black stain along the top of the truss chord. All signs of past moisture trouble in that attic.

The problem may have been dealt with, causing the surface coating to dry out and flake off. I don't know what those flakes taste like, so can't tell you what they are.

A new roof was installed in 2009. The place was built in 78. Moisture could be the source. I have just never seen black mold or other substance flake like that. Should I known I could identify by eating one I would have

Hi Chris,

It's hard to say from the picture, however, I have seen something that looks a lot like your picture. I was inspecting an older home that had a fire about 4 years prior to the inspection.

I have a friend in the fire and water restoration business. He told me that during fire restoration, it's common to coat materials that were not burned (but had soot and smoke odor) with Kiltz or a similar type stain blocker to seal the odor from permeating the area in the future. The better way to do this now is dry ice blasting.

Looking at the truss in your picture, it looks like the top near the sheating was sprayed with something which is why I believe this may be the case. The sealer may be flaking off of the sheathing from years of 150 degree plus temps.



Here is a picture of a fire restoration job where the sheathing was replaced, but the rafters were left since they only had soot on them. They are being cleaned with a dry ice blasting cleaning procedure.

Is there any particular odor that you noticed? (musty, burnt, etc.)


Andrew Constantine
InspectPro Home Inspections
Licensed in SC and NC
Charlotte Home Inspection News

No strange odor. I pulled a flake down and stuck it right up to my nose. No charring smell was present

Might be clear shellac or silver paint post smoke remediation flaking off (not surprising after years of drought and hot summers), even from off-site generated smoke drawn into the attic from past events. Not sure if I'm seeing shadowing or similar finish on the side of truss chord to the right nearest the decking.However I also suspect late 70s vintage FRT plywood decking exposed to higher temperatures in the low-slope poorly ventilated minimal attic space so common to your region of construction of that decade and the one prior.More likely if the home was one of literally thousands of pre-fab modular construction developments in your area of that same vintage. Even more likely if the home was a manufactured or mobile home of the period.North side decking cooler, retains slighly longer snow fall, less exposure to direct sunlight, faster to cool, more prone to condense moisture slower to dry out. Less than ideal natural ventillation, even in the more arid environment.Which side are venting and exhaust ducting present or were present? Which side (north?) of the home is the back yard (outdoor cooking, pleasure fires, pre drought periods, etc.) Evidence of past or present turbine or similar mechanical attic space ventillation?

yes there is a power ventilator installed. Probably after the condition was found.

Originally Posted by H.G. Watson, Sr.

..However I also suspect late 70s vintage FRT plywood decking exposed to higher temperatures in the low-slope poorly ventilated minimal attic space so common to your region of construction of that decade and the one prior

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Top Five Failed Building Practices: Part 2 of 5 Fire-Retardant Treated Plywood | U.S. Inspect
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