Primers to Fill-in Cracks Before I Stain a Deck

How Primers Work

• A good primer forms a firm bond to the painted surface, prevents unwelcome stains from bleeding through to the topcoat, and provides an optimized surface for the topcoat to adhere to. Primers can be formulated in oil-based or water-based versions for any numbers of surfaces, such as foundation walls, aluminum siding and indoor drywall. There are also primers designed specifically to help deal with the challenges unique to aging deck timbers, including splitting and cracking. For best results, use a primer formulated specifically for decks on your decking lumber.

How Deck Stains Work

• Wood toners and semi-transparent stains are pigmented coatings designed to penetrate into the decking planks and provide color from within the wood, while allowing the wood's natural grain and knot structure to remain apparent. A solid color or opaque stain forms a film on top of the wood's surface that conceals the grain, but allows the texture to remain visible. By contrast, a paint will form a film that conceals the wood texture. Unlike paint, a solid color stain presents an extremely flat sheen that is completely gloss-free.

How To Prime Before Staining

• It is only appropriate to prime a deck when you plan to follow up with a solid color stain. Before applying a primer over the entire deck, you should first spot-prime any cracks or fissures using a brush to poke thoroughly into any crevices. Then spot apply the primer to the cut ends of the individual timbers. Most deck primers are opaque and all primers are designed as a barrier coat, so you should never use a primer before applying a semi-transparent stain.

Environmentally Safe Primers and Stains

• Alkyd-based primers and stains usually release a much higher level of VOCs (volatile organic content) into the air when the paint is applied than their water-based counterparts. VOCs contribute to smog and to global warming, and they may also irritate the eyes and respiratory systems of the person applying the coating. Alkyd coatings contain petrochemical solvents that will damage some plant life if spilled on the ground. Check the primer and stain labels for approval by third-party environmental groups such as Green Seal or Scientific Certification Systems.