Deck Stains & Coatings

Clear Finishes and Water Sealers

• Exposed wood can crack or warp from exposure to rain, snow and ice, so clear sealants are designed to create a barrier that prevents water from infiltrating the wood. While sealers can differ in many ways, the most important difference to consider is whether it is penetrating or film forming. Film-forming sealers are a transparent barrier that sits on top of the wood, and that means that they will wear off as a result of foot traffic. Some lower-price water sealers use paraffin as the water repellent, and these may last as briefly as three months. A penetrating clear prevents water infiltration by filling the pores in the top section of the wood while forming a light film on top, and these coatings will typically provide a year or more of protection.

Wood Toners

• A wood toner uses a penetrating oil to fill the wood's pores and limit water infiltration while adding some pigment that enriches the color of the lighter wood tones. The pigment will also help protect the wood from the sun's ultraviolet rays which will, eventually, cause a deck to turn gray. A toner will protect wood from rain and snow, but because it does so within the wood rather than on its surface, it will not cause water to bead up and it will not be as vulnerable to foot traffic. Properly applied, a good toner should be effective for one to two years.

Semi-Transparent Stains

• Semi-transparent stains will darken light color timber overall and reduce the visual contrast in the grain pattern. These stains are usually supplied in wood-tone colors plus one or two shades of gray that simulate the look of weathered or bleached timbers. A high-quality wood stain will fill the wood's pores to inhibit water absorption without actually causing the beading effect of paraffin water sealers. In addition, a semi-transparent stain will contain pigments that help protect the wood from ultraviolet rays that would cause the decking to become gray and brittle. Higher quality exterior wood stains will utilize transparent iron oxide particles, an automotive paint ingredient that serves to block UV rays without darkening the finish itself.

Solid Color Stains

• Solid color stains conceal the natural color of the wood by penetrating within its top layer and forming an external film. The most noticeable difference between a solid color stain and a porch paint is that the texture of the wood is still quite apparent with this class of stain. A good quality solid color stain will also outlast a porch paint and do a better job of holding up to foot traffic. While this type of finish is acceptable during any stage of a deck's life cycle, it is most commonly used after the planks have aged and lost much of their original color.

Oil Versus Water

• Oil finishes do a better job of penetrating into the wood's surface, so they tend to last longer than water-based finishes. Oil- or alkyd-based stains are not without their drawbacks. For one, they depend upon much higher level of volatile organic compounds, which contribute to air pollution. For another, they can be vulnerable to mold when used in humid areas. By contrast, water-based deck finishes use artificial resins that do not feed mold growth. Some newer formulas of water-based deck coatings employ nanoparticle technology to do a better job of penetrating into the wood itself, so these may serve as a practical alternative to oil or alkyd coatings if you are willing to pay the higher cost of these products.