Plywood is a flexible wood material used in the construction of houses, sheds and other buildings. The material, like other wood, is not resistant to moisture and other weather elements when used outdoors. To keep exterior plywood from rotting, it is important to seal the wood with a water-repellent sealer that also prevents the wood from peeling. In addition, sealers keep mould and mildew from forming on the wood's surface.
Place a dust sheet or plastic sheeting on the ground below the exterior plywood you want to seal. Wear latex gloves to keep the sealant off of your hands.
Wipe the plywood with a soft cloth or rag to remove any loose dust and dirt from the surface.
Apply a generous amount, 4 to 5 tbsp at a time, of water-repellent sealer to the plywood's edges and overall surface using a paintbrush. Start at the edges and work inward.
Continue applying sealer until the plywood is completely covered. Let the sealer air dry for two days before applying paint or stain.
Wash the paintbrush by pouring paint thinner over the bristles and then running the brush under warm running water to remove any residue. Dry the brush with a clean, soft cloth or rag.
If sealing a large piece of flat exterior plywood, use a paint roller to apply the sealer to the flat areas and a paintbrush to apply it to the edges.