Are the black spots on my OSB mold? If so, should I be concerned? We had a problem with vent but has been corrected. Thanks.
Image is of worse area in attic.
Best Answer
That is mold. Assuming this is what it looks like after it's been sufficiently dried so more mold won't develop beyond what we're seeing here, that is surface mold isolated within a wall cavity, and you've got nothing to worry about.
Typically, if it is surface mold or the decayed portion of the wall system is small enough to be safe and acceptable, you would leave it alone, as molds become dormant below 20% WMC (your framing should be between 12% and 16% once fully dried and ready to be closed back up), as long as the following criteria are met:
If the sheathing was never saturated (or above 28% WMC) or if the saturation was limited (in a non structural wall);
If the moisture problem has been remedied (dried and not going to get wet again); i
If it will not be disturbed, so as to spread spores into living space; and,
If the decay is surface only (has not transmitted through to the other side of the sheathing is a good indicator of compromised sheathing).
Best practice would be to replace the sheathing in the event any of the above are not met. Cost of doing the repair vs cost of not doing the repair will drive the decision, except in the case of damage to a critical building component in which case the cost of not doing the repair is also a question of safety/liability.
The Illinois DPH site related to mold, which does not specifically license remediation firms.. They also don't do inspections. They DO list several internet sites for contractors:
It might be a pertinent question to ask: "Do you follow the EPA guidelines for remediation?".
A basic tool for your own use, a moisture gauge, will tell you if the area is ready for treatment: Wooden interior framing should be < 15% moisture content. One reasonably accurate meter (non-contact) is the Ryobi E49MM01.
A good remediation company will do testing on both surface and air afterwards. I would make sure there is a good amount of time past after cleaning to go through and do the tests - a couple weeks maybe.
Your main concerns are basement and bathroom, so make them prove those areas too you. If there is a lot of ongoing mold on a wall the it is likely it affected the surrounding areas. So make them open up walls to prove there is nothing. If they don't want to then I would expect the worst and know that first you might have more big issues that are hidden and two that you might need to do a lot of drywall and finishing touch work after you demo sheetrock in areas.
Note: I would also try to put some of the risk onto the remediation company. If I have to use one on flips we go over everything. I get a price. And then if they mess up they come out and fix the area for free. For instance if they tell you that you don't have mold in a room but find it a month later they would come out and remove wall and fix area. You have to get a reputable company and then you will usually only be given 3-6 months. If you think the house was full of moisture/humidity for a long time then I would assume that most of my drywall has to be replaced. For a 2000 sq ft house that is 10-15K. Also know too, mold needs moisture. If there is a little mold in a wall and it never gets more moisture, there is little to no harm... I will say this, I rather deal with termites than big mold when buying a house.
Best Answer
That is mold. Assuming this is what it looks like after it's been sufficiently dried so more mold won't develop beyond what we're seeing here, that is surface mold isolated within a wall cavity, and you've got nothing to worry about.
Typically, if it is surface mold or the decayed portion of the wall system is small enough to be safe and acceptable, you would leave it alone, as molds become dormant below 20% WMC (your framing should be between 12% and 16% once fully dried and ready to be closed back up), as long as the following criteria are met:
Best practice would be to replace the sheathing in the event any of the above are not met. Cost of doing the repair vs cost of not doing the repair will drive the decision, except in the case of damage to a critical building component in which case the cost of not doing the repair is also a question of safety/liability.