Thread: 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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did you take any pictures?

Originally Posted by wayne soper

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

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.

Could it be Celotex that you were looking at?

Try this to resize the image:

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

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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.

Originally Posted by Nolan Kienitz

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"

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

Originally Posted by Mike Krueger

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

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

Originally Posted by Jon Errickson

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

LOL

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.

"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.

Originally Posted by Roger Hankey

"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

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.

Originally Posted by Jim McMillan

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.

Originally Posted by JB Thompson

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

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 !