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Thread: Black OSB

  1. #1
    Andy Jarchow's Avatar
    Andy Jarchow Guest

    Default Black OSB

    Hello,

    Just did an inspection this afternoon. Bathroom fan was vented to the soffit. In the attic I notice the OSB was black in a 2’x2’ area where the bathroom vent is. Is this black color a mold like/growth?

    The OSB in this area seemed solid yet. If it is mold should I recommend it be removed/cleaned up or will it go away if they eliminate the moisture-route the fan through the roof…?

    Thank you for your advice!
    mk

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  2. #2
    Join Date
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    Default Re: Black OSB

    did you take any pictures?


  3. #3
    Andy Jarchow's Avatar
    Andy Jarchow Guest

    Default Re: Black OSB

    Quote Originally Posted by wayne soper View Post
    did you take any pictures?
    Yes but can't get them to work on this site. They say they are too big and I'm not sure how to make them smaller.
    Sorry


  4. #4
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    Default Re: Black OSB

    Just report what is there - black stain on OSB. Could be a moist area in the attic.
    Recommend a repair to the exhaust fan vent pipe.
    Explain that the growth needs moisture to grow and spread spores blah blah blah, but I don't make a big deal over some stain in the attic.

    I can find stains in my attic, from old leaks.


    John Kogel, RHI, BC HI Lic #47455
    www.allsafehome.ca

  5. #5
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    Default Re: Black OSB

    Could it be Celotex that you were looking at?

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  6. #6
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    Default Re: Black OSB

    Try this to resize the image:

    resizeimage.org - Resize images with ease

    -Jon
    Errickson Home Inspections, LLC
    http://www.erricksonhomeinspections.com

  7. #7
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    Default Re: Black OSB

    IrfanView is great for manipulating images and it's free. Download it here.

    IrfanView - Reviews and free IrfanView downloads at Download.com


  8. #8
    Nolan Kienitz's Avatar
    Nolan Kienitz Guest

    Default Re: Black OSB

    Such noted mechanical exhaust fans are required to be vented to the "exterior envelope" of the home and NOT INTO the ATTIC.

    Those fans are for the use of removing moisture/humidity from bathrooms, utility rooms, etc.. If they are not vented to the "exterior envelope" (IE; through sidewall or through roof decking) they could allow the collection of humidity/moisture in the attic space and at the bottom of the roof decking and allow mold/mildew to collect.

    Simply say installed incorrectly and resolution is to extend the venting the "exterior"of the home's envelope.


  9. #9
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    Default Re: Black OSB

    Quote Originally Posted by Nolan Kienitz View Post
    Such noted mechanical exhaust fans are required to be vented to the "exterior envelope" of the home and NOT INTO the ATTIC.

    Adding a few important words to clarify the above, those words are in bold and red:

    "are required to be vented to the outdoors, i.e., "to the exterior of the building envelope" of the home and NOT INTO the ATTIC"

    Jerry Peck, Construction / Litigation Consultant
    Construction Litigation Consultants, LLC ( www.ConstructionLitigationConsultants.com )
    www.AskCodeMan.com

  10. #10
    Andy Jarchow's Avatar
    Andy Jarchow Guest

    Default Re: Black OSB

    Thank you Jon and Rober for the resizing sites. I tried them both and found that http://www.resizeimage.org/ was the easiest one to use. Here are the photos.

    The bathroom fan was vented to the outside but the normal air flow (up the soffit vent out the ridge vent) was pulling the moisture back into the attic through the soffit vents. They have since blown in more insulation and didn’t put any baffles in this area so it may solve the issue.

    Thank you all for your help. If you can add any more info now that I have photos I would appreciate it.

    Have a great weekend!
    mk

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  11. #11
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    Default Re: Black OSB

    Quote Originally Posted by Mike Krueger View Post
    Thank you Jon and Rober for the resizing sites. I tried them both and found that http://www.resizeimage.org/ was the easiest one to use. Here are the photos.

    The bathroom fan was vented to the outside but the normal air flow (up the soffit vent out the ridge vent) was pulling the moisture back into the attic through the soffit vents. They have since blown in more insulation and didn’t put any baffles in this area so it may solve the issue.

    Thank you all for your help. If you can add any more info now that I have photos I would appreciate it.

    Have a great weekend!
    mk
    Yep looks like mould

    appears like there is a lack of proper venting in that specific area


  12. #12
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    Default Re: Black OSB

    It's hard to tell what's going on... can you make the images bigger??

    -Jon
    Errickson Home Inspections, LLC
    http://www.erricksonhomeinspections.com

  13. #13
    Andy Jarchow's Avatar
    Andy Jarchow Guest

    Default Re: Black OSB

    Quote Originally Posted by Jon Errickson View Post
    It's hard to tell what's going on... can you make the images bigger??
    LOL


  14. #14
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    Default Re: Black OSB

    Looks like the flex to the soffit vent is broken/disconnected - very common problem near the eaves and where the flex turns down to the vent termination, if I can get there I usually dig out the exhaust duct and take a picture of the defect.

    Michael Thomas
    Paragon Property Services Inc., Chicago IL
    http://paragoninspects.com

  15. #15
    Roger Hankey's Avatar
    Roger Hankey Guest

    Default Re: Black OSB

    "The bathroom fan was vented to the outside but the normal air flow (up the soffit vent out the ridge vent) was pulling the moisture back into the attic through the soffit vents. They have since blown in more insulation and didn’t put any baffles in this area so it may solve the issue. "

    The action taken - adding more insulation - is NOT likely to help. As stated by others, the fan should vent outside. This fan is directed to the outside but the moisture will still come back inside. (The insulation doesn't stop the fan air flow, it just slows it down, so it is even more likely to condense on the OSB. More insulation in this area will likely worsen the problem since in winter the roof deck will be colder longer. I would recommend that the fan be ducted up through the roof sheathing with a proper vent terminal installed by a qualified roofer. (Option - replace the blackened OSB when the vent terminal is being installed) The fan duct should be insulated material that is securely fastened and sealed to the fan and the the vent terminal. Securely fastened means such that during a reroofing, the duct will remain connected to a flange secured to the underside of the sheathing. (since the vent terminal may be removed as part of a shingle tear off). Another advantage of venting up through the roof is that the status of the duct can be viewed from the attic, and the status of the fan performance can be checked from the rooftop.


  16. #16
    Andy Jarchow's Avatar
    Andy Jarchow Guest

    Default Re: Black OSB

    Quote Originally Posted by Roger Hankey View Post
    "The bathroom fan was vented to the outside but the normal air flow (up the soffit vent out the ridge vent) was pulling the moisture back into the attic through the soffit vents. They have since blown in more insulation and didn’t put any baffles in this area so it may solve the issue. "

    The action taken - adding more insulation - is NOT likely to help. As stated by others, the fan should vent outside. This fan is directed to the outside but the moisture will still come back inside. (The insulation doesn't stop the fan air flow, it just slows it down, so it is even more likely to condense on the OSB. More insulation in this area will likely worsen the problem since in winter the roof deck will be colder longer. I would recommend that the fan be ducted up through the roof sheathing with a proper vent terminal installed by a qualified roofer. (Option - replace the blackened OSB when the vent terminal is being installed) The fan duct should be insulated material that is securely fastened and sealed to the fan and the the vent terminal. Securely fastened means such that during a reroofing, the duct will remain connected to a flange secured to the underside of the sheathing. (since the vent terminal may be removed as part of a shingle tear off). Another advantage of venting up through the roof is that the status of the duct can be viewed from the attic, and the status of the fan performance can be checked from the rooftop.
    I did recommend they route the fan out through the roof.

    Thank you all for your good advice!

    Thank you to all of our service men/women and vets.!!! God bless you.

    Have a great weekend.
    mk


  17. #17
    Jim McMillan's Avatar
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    Default Re: Black OSB

    If what I see is correct it looks as if there is a nail penetrating the OSB sheathing, not that this should be unexpected since it is a roofing nail. But the inspections that I have done that have a similar staining on the OSB have usually had a leak through the roof covering. Have you checked the roof covering (shingles?) closely in the general area of the stain?

    Possibly consider a report entry such as this: "Stains were noted on the underside of the roof sheathing at (location) during the attic inspection. The area could not be adequately accessed in order to closely investigate further due to limited accessibility. Stains are often due to excess moisture and may be a result of a leak in the roof sheathing or possibly a problem with the bathroom ceiling mounted exhaust fan. Further evaluation is needed in order to determine the exact cause of the staining". Say what you see, share what knowledge and experience you have and don't guess.


  18. #18
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    Default Re: Black OSB

    Quote Originally Posted by Jim McMillan View Post
    If what I see is correct it looks as if there is a nail penetrating the OSB sheathing, not that this should be unexpected since it is a roofing nail. But the inspections that I have done that have a similar staining on the OSB have usually had a leak through the roof covering. Have you checked the roof covering (shingles?) closely in the general area of the stain?

    Possibly consider a report entry such as this: "Stains were noted on the underside of the roof sheathing at (location) during the attic inspection. The area could not be adequately accessed in order to closely investigate further due to limited accessibility. Stains are often due to excess moisture and may be a result of a leak in the roof sheathing or possibly a problem with the bathroom ceiling mounted exhaust fan. Further evaluation is needed in order to determine the exact cause of the staining". Say what you see, share what knowledge and experience you have and don't guess.
    I agree with Jim. From the photo you sent, this looks more like a leak in the roof covering.

    Bruce Thompson, Lic. #9199
    www.TylerHomeInspector.com
    Home Inspections in the Tyler and East Texas area

  19. #19
    Andy Jarchow's Avatar
    Andy Jarchow Guest

    Default Re: Black OSB

    Quote Originally Posted by JB Thompson View Post
    I agree with Jim. From the photo you sent, this looks more like a leak in the roof covering.
    I did my regular roof inspection and then went back up to specifically check this area. The sheathing seemed solid and there were no obvious reasons for a leak so I assumed it was from the bath vent (being it was in the same spot). The roof was put on in 07 and still looked good. I suppose it could be old damage too.

    Thank you for your help all.

    mk


  20. #20
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    Default Re: Black OSB

    Hi ALL &

    Most probably mildew /mold - regardless of 'why', but one thing's for sure -- that is not going to 'go away' until /unless cut-out...


    CHEERS !

    -Glenn Duxbury, CHI

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