OSB (oriented strand board) is a manufactured wood product that contains striated fibres of wood, held together using a strong resin glue. The edges that are cut during the milling process are coated with a waterproof paint to seal them from moisture. When working with OSB to build a sub-roof, subfloor or side wall, any new edges created by cutting should ideally be sealed using the same, or similar process. Taking a little extra time to protect the integrity of the wood makes it a project that will last for years.
Use a measuring tape to mark off the needed length and width of OSB. Cut the wood using a circular saw. Setting the large sheets of OSB on sawhorses will make the job of cutting them easier.
Mix a can of exterior waterproof paint using a stir stick. Use a small paintbrush to coat all newly cut edges.
Allow the paint two hours to dry. Add a second coat to any areas that are missed, or appear thin.
Give the wood an additional two hours of drying time. Install the OSB as normal.
For additional strength in OSB wood, purchase a grade that is marked "exposure" and "exterior." It is the most durable grade on the market. Only use products that are true OSB. Tim Carter of Ask the Builder states, "There are products out there that look like OSB. Waferboards, flakeboards and such are not OSB. When you use OSB for a roof sidewall or subfloor it MUST have the APA label. If it doesn't, don't use it."
Wear safety glasses when cutting and painting OSB wood. Paint the edges in a well ventilated area.