Builders have used treated plywood as an exterior siding for homes since the 1940s, according to a publication issued by the North Central Regional Extension. Treated exterior plywood tends to be manufactured with a rough finish, as opposed to the smoother exterior of natural wood boards. While the rough texture holds up well to the elements, it can make the plywood a little more difficult to paint. Homeowners painting treated plywood need to use materials that can both adhere to plywood and withstand nature's fury.
Paint treated plywood only after the lumber dries completely and the treating materials absorb fully into the wood. Wait anywhere from several weeks to several months for newly treated wood to dry, depending on the heat and humidity in your location.
Clean the plywood prior to painting. Scrub away any existing flaking paint with a wire brush. Wipe the surfaces thoroughly with a dampened rag. Allow the plywood to dry before continuing.
Brush water repellent or water-repellent preservative along the faces and edges of the treated plywood. Allow the repellent to dry for a minimum of two days.
Apply a coating of oil-based exterior primer to the plywood. Touch up any textured nooks in the plywood with a paintbrush to ensure complete coverage. Paint the primer on thick enough that the grain of the wood is not visible underneath.
Allow the primer to dry completely for at least two days. Wait no longer than two weeks before applying the first coat of paint.
Apply a coating of exterior latex paint. Use the highest-quality paint you can afford for the best results. Allow the paint to dry completely, and then apply a second coat of exterior latex paint.
Inspect the cleanliness of the paint job after the second coat of exterior latex dries. Apply more layers of paint as necessary to achieve blemish-free plywood.
Home improvement expert Danny Lipford recommends mixing a mildewcide into the primer and paint if the plywood will be exposed to frequent damp conditions.
Pressure-washing cleans more thoroughly than a rag, and works faster when you're preparing large amounts of plywood for painting.