Oriented strand board consists of several layers of wood particles that are bound by an adhesive and compressed tightly together into a 4-by-8-foot panel. You can apply virtually any type of topcoat on OSB, but it is best to start with a primer that will block the transfer of moisture that can cause the panel to delaminate.
Acrylic Latex Primers
If your OSB panels are used indoors, an acrylic latex primer will be an ideal base coat because it's so easy to work with. Latex primers are fast-drying, so they can be painted over in as little as an hour. They are nearly odor-free and do not contribute to indoor air pollution. At the same time, these moisture-barrier primers provide a sound footing for all types of interior latex paint.
If your OSB panels will be exposed to moisture or high humidity, your base coat should be an alkyd -- also known as oil-based -- primer sealer. This type of base coat blocks the flow of moisture to and from the panel to form a lasting protective barrier. These primers can be used under both latex or alkyd paints.
Liquid House Wrap
If you're planning to paint your exterior OSB sheathing, a fluid-applied air- or moisture-barrier coating can serve the same purpose as a plastic house wrap and still allow your OSB panel to be topped with a conventional paint or a stucco finish.