1. Select the right kind of waterproofing which works best for plywood. Deck waterproofing is easy to apply and it dries quickly. But this kind of waterproofing eventually deteriorates, requiring subsequent coats over time. If the plywood is the subsurface for a deck, choose a more permanent waterproofing material with an oil base.
2. Assemble the plywood and material we need to complete the job. The sawhorses are useful when applying waterproofing because it keeps the plywood level and easy to reach. The best place to apply waterproofing is outside the house because the smell evaporate and do not concentrate inside the house.
3. Apply the waterproofing according to the directions on the original container. If the outside of the plywood panel is decorative, wipe the plywood down with a damp cloth and sand it lightly with 120- to 220-grit sandpaper to smoothen the face of the plywood once the panel dries. By wetting the plywood the grain is slightly raised. After sanding the grain down, the surface will be smooth after applying the waterproofing material. Waterproofing material deck waterproofing is easy to apply with a simple brush. If you are using an oil-based waterproofing material brushes may render the best coverage.
4. Flip the plywood over and apply the waterproofing material to the other side. Apply waterproofing to all the edges of the plywood to create an impervious surface.