Any ideas what this is on the underside of the roof sheeting in an attic?

(Mark A. Oliverio) #1

Looking for a little help here. This is the underside of the roof sheathing, plywood sheets, almost all of them were dark in color but a few had this on it, almost looks like it is charred from a fire, but nothing in disclosures. To the touch, it was slightly oily.The other thought was an exhaust from over the stove/oven, but it appears to terminate outside the attic.
This is on a house in the northern suburbs of Detroit Michigan, house was built in 1965, ranch style house. Access into the attic was difficult and there was also rolled insulation on the floor of the attic. Ridge vent with Gable and Eave vents with baffles installed. Any help would be appreciated.

(Marc A. Goldenberg, Inspector Lic # HI1365 Mold Assessor Lic #1) #2

I don’t see a picture . . . . :cowboy_hat_face:

(Mark A. Oliverio) #3

This would help, wouldn’t it!

(Marc A. Goldenberg, Inspector Lic # HI1365 Mold Assessor Lic #1) #4

Looks charred to me caused by a fire.
How do you know that the stove/oven did not cause it in the past.
Was it mostly everywhere, but concentrated more in one area.

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(Mark A. Oliverio) #5

It appeared the entire underside was darkened, though I couldn’t make my way around the entire attic. There was two sections, like the one in the pic, that had the flaking or charred look to it.
Here’s another pic of the attic.

You can see where some of the wood looks clean where the ones supporting the roof sheeting are darkened.

(Joseph Jacono) #6

Think you need to get a sample of that tested. First impression is it’s result of a fire, could be fungal growth, but really looks like smoke damage. I would expect if there was a fire the trusses would be covered, unless those had been wiped down from a remediation company. Other issue is the OSB appears to be delaminating. Assuming that’s 7/16" OSB on 24" centers, that roof is possibly spongy and weakened due to flaking/delaminating. Once OSB comes apart like that it’s pretty much done.

(Michael R. Boyett, TREC #7290 (Ret) Boerne, TX) #7

You might want to look into and rule out, if possible, the Fire Resistant Treated (FRT) plywood that began to be used extensively in the '60’s and then started showing similar signs of degradation years later. This white paper ( ) says:

Deterioration of the FRT plywood is visually recogniza­ble. Interior views of attic spaces have confirmed that the underside of the wood darkens significantly (see Figure 1). A characteristic dark, reddish-brown, charred appearance is often evident.

(Roy Lewis, CMI - North Florida Inspector) #8

Its smoke damage.

(William B. Ogletree, TREC License #22530) #9

At first glance it looks like smoke damage, but then I have to wonder why the diagonal web members appear to be unaffected. Also that it covers the “entire underside” makes me wonder as well.

Definitely get it tested.

(W Eric Stocker) #10

Did it smell smokey? If moisture condensed on under side of roof, then what ever it is would stick to the moisture and not the rafters that do not have moisture on them. Smoke in winter? Mold or fungi. I think it needs tested.

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(Jim Ward) #11

Have seen lots of this. poor attic ventilation, so fungi growth. Lots of times people plugs batts of insulation around the attic perimeter not realizing they plugged the soffit vents. Undersize gable vents will also do this. Hope this helps. I am from Southwestern Ontario so similar weather

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(Douglas Cossar, CMI. NHI) #12

Agree with Roy… Smoke damage


(Mark A. Oliverio) #13

Update: It is being tested for mold. Seller advised Realtor that when they bought the house 10 years ago that the sellers told them that after the roof was replaced, there was not enough ventilation in the attic and after a year of under ventilation, that the sheathing darkened in color (more vents were added). The current seller also stated that he has never looked up in the attic as there was no need so he had no idea to what it looked like now. If you look under Michael Boyett’s reply to this and read under the heading “SHORTCOMINGS IN DESIGN - THE DEGRADATION PROCESS” paragraphs 3 and 4 are exactly what I saw in the attic and roof though the waviness of the roof was very minimal at best.
My report has been amended to include all of your theories (thank you one and all) and the client and realtor have been advised of all of this and now the ball is in their court as to what they are going to do.
Thanks again to all of you for the quick responses, it’s awesome knowing that there is help out here when situations arise.
God’s Blessings on all of you!

(Roy Lewis, CMI - North Florida Inspector) #14

Bull shit! Yep!
What is the matter with all you people.

Off the cuff! OK?
*"We noted the roof sheathing appeared to have smoke damage. *
We recommend further evaluation by a licensed professional…"
And let it go!
That is smoke damage and I’d be willing to bet on it…Yes!
See it too many times in the past.

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(Robert Young) #15

I highly suspect Mold but do not take anyone’s word.
There was/is a film of peeling residue on the underside of the sheathing yet not on the upper chords or roof joists.
Look at the upper chords. Black and White staining. No peeling dried film.

What material is the roof covering, Mark? Just curious. Tile roof?

Recommend testing. Advise us on/of the results if/when you get them.

Smoke would have stained the upper chords as well.
What neck of the woods are you located, Mark?

(Joshua L. Frederick) #16

Me too…definitely not from smoke! LOL. I would be careful to “blame” it on lack of ventilation though. Usually has to do with moisture sources/air leaking into the attic via bath & kitchen fans, attic bypasses, etc.

(Robert Young) #17

Morning, Joshua. Hope to find you well and in good spirits this morning.:smiley:

Josh, I see no ridge vent.
As well, the roof looks low slope. Under 4/12.

In my opinion, a ridge vent would insure the best roof deck ventilation.
To deter over venting, soffit vents can be organized along the underside of the roof eave to impede over venting the attic space.
Just my opinion.

Sorry for the edits. Trouble with emoji’s.

(Marc A. Goldenberg, Inspector Lic # HI1365 Mold Assessor Lic #1) #18

Hey Robbie!
How come your picture looks like a deer in the headlights? :cowboy_hat_face:

(Robert Young) #19

Hi, Marc. Hope all is well in your neck of the woods.

I do not understand. Something wrong with my Nachi thread image?
Never really look at myself, if you know what I mean.
Please advise.

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(Roy Lewis, CMI - North Florida Inspector) #20

He is just jokin’ with you.

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