OSB, or Oriented Strand Board, is an engineered wood product formed by layering strands of wood together and has a rough surface. It is commonly used as sheathing in walls, floors and roofs and is preferred over plywood due to its low price and uniformity.
Mold is a common problem in moist areas or places that are prone to flooding or leakage. Since OSB is a cellulose-based material, most of the time it already contains mold spores and only requires moisture to trigger the growth process. Mold is quite dangerous and full exposure to it should be avoided at all costs. Some varieties of mold are toxic while others are infectious and can result in rashes, eye infections and other health problems.
Step 1 – Taking Appropriate Safety Precautions
Since mold can be infectious or toxic, wear gloves, a mask and goggles to prevent inhalation or infection. Seal off any vents close by to prevent any disturbed mold spores from spreading and handle any contaminated items very carefully. Check whatever chemical products you use to see whether you need to wear respirator masks or other safety equipment while handling them. If you are pregnant, have someone else perform this task for you.
Step 2 – Locating the Mold
Mold is not always easy to see – most of the time, it is of a different color than the material it is on, but if you have painted the OSB a dark color, it may be difficult to spot. Use a flashlight and shine the beam along the surface of the OSB – this will reveal the mold no matter what the color, due to it being three-dimensional.
Step 3 - Removing Fresh Mold
If the mold is not very old, ordinary detergent and water may remove the mold. Slowly wipe the OSB surface with a washcloth soaked in warm soapy water, rinsing it frequently.
Step 4 – Removing Old Mold
If the mold has been present for a while and really taken a hold on the OSB, fill a sprayer with a 10% bleach solution and set it to the mist setting. This is important as using the stream setting would cause the stream to dislodge spores and lead to further contamination. This effectively kills the mold. However, more porous surfaces find chemical biocides to be more effective as they do not leave any moisture behind.
The most effective chemical biocide for killing mold is Sporicidin, which also prevents a recurrence of mold. It is the only biocide approved by the Environmental Protection Agency for indoor use and does not stain surfaces like bleach does. It has a pH level of 7.5 which means it can be painted over later, which is especially important if your OSB is indoors. Follow the instructions on Sporicidin or your biocide of choice to kill the mold most effectively. Leave the biocide on for at least ten minutes to allow it to absorb into the OSB completely, and reapply if necessary. Sporicidin and other biocides need to be ordered through an authorized dealer.
TIP: To keep mold from coming back, apply waterproof solutions (and paint, if desired) to the OSB to keep moisture from getting into it in the future.