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Old 02-28-2012, 03:56 PM   #1
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Mold and OSB Sheathing

Hi All,

I am new to the site but am excited by all of the great information I have already found! A question for all of you experts. I just left a home inspection for a home I am buying and, unfortunately, we found mold in the attic. The problem was pretty bad. The inspector said he would not move his family into the house without replacing the entire roof + sheathing. He said the problem is the sheathing is OSB and it is almost impossible to fully clean. It was also wet to the touch. Does anybody have experience with this and, if so, how have you remdediated the situation? I trust the inspector, who is also a certified mold technician, but I thought I would check what he was telling me. I want to do what is right and safe for my family.

Thanks in advance!


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Old 02-28-2012, 05:11 PM   #2
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if it's that bad replace it,but find out why it was so wet


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Old 02-28-2012, 07:01 PM   #3
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I am a little puzzled. If the house is that bad, and it sounds pretty bad, why are you buying it? There are thousands of houses out there, go find one that does not have severe problems.
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Old 02-28-2012, 07:13 PM   #4
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Not all that uncommon.
Things that can cause it are the shingles needed changing years ago and they just put it off.
No ventalation in the attic.
Shingles and flashing were installed wrong.
Chimmny or it's flashing leaking.
If there was nothing else wrong on the report, get a price to fix it and take all of it and some extra off the offer to buy.
More then likly the rafters will also need to be checked and at least treated with a product like Timbor to kill the fungus.
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Old 02-29-2012, 03:39 PM   #5
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I used to work for a remediation company. I did most of the inspections. Many of which were in this exact situation of a pending home sale. If the OSB is wet nearly all-over rather than just in certain spots then it is a fair bet that the shingles are keeping the water out. What is likely going on in this situation is a combination of inadequate insulation and ventilation. If the insulation between the attic space and the heated part of the house is inadequate then the heat from the house is getting up there and just like water condenses on a cold glass the water vapor condenses on the attic ceiling that is colder than the air in the attic. I do not know where the house is but I assume that it is closer to Canada than the Caribbean. Really, the only way to remedy that is a full removal and replacement including the addition of insulation(r-value Zone Map)and ventilation. There should be a ridge vent, soffit vents, and gable vents. People worry about having too much ventilation because they feel that there is heat loss. If the insulation is sufficient then all that is happening is a temperature/humidity balance with outside air. The balance is key, bad things happen when attic temperature and humidity do not coincide with the outside environment. I have done several jobs that involved removing even the trusses. This is shockingly common. An easy way to check the insulation from outside is by looking at the roof. If there is snow on the overhang of the roof and less or none over the attic then the house is sending heat into the attic causing it to melt. It would be safe to say that there is condensation and mold in that situation.

Not good news but I hope this helps.
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Old 02-29-2012, 03:58 PM   #6
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Originally Posted by Tom Struble View Post
if it's that bad replace it,but find out why it was so wet

Ventilation, bulk moisture, etc.

Replacing the roof, if it was a ventilation issue, may do nothing to change the formative cause of the problem and will just get you new sheathing that is going to mold right back up.
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Old 03-01-2012, 07:03 PM   #7
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I agree with the other poster's good comments about attic ventilation.

I estimate that 95 percent of the past 50 attics I have been in had mold/moisture problems as a result of inadequate ventilation.

Sadly, I have seen some attics that were re-sheathed a few years ago, that are already starting to deteriorate again, because they did not fix the problem when the replaced the sheathing.

I have a short article with some ventilation information that maybe helpful:


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attic , mold , osb , roof , sheathing

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