Finishing touches for treated wood

coating. In most cases, two to three weeks of seasoning in dry weather should bring the moisture content down to an acceptable level.

Substrate Limitations. Southern pine is the most commonly CCA treated species. Its properties enhance its treatability-but work against it as a coatings substrate. In general, southern pine has poorer finish-holding capabilities than cedar or redwood. However, the deleterious effects are somewhat offset by the performanceenhancement properties of the CCA.

Because they are film-forming coatings, they tend to peel, blister and mar when coated on horizontal substrates subject to weathering and traffic.

Clear or pigmented water repellents, wood toners and semi-transparent stains are the most common deck finishes. To work properly, they must penetrate the surface.

Improper Surface Preparation. Surface preparation is integral to the ultimate performance of coatings for any wood surface. Surfaces must be clean, dry, and free of mildew before coatings are applied. The better preparation products will remove dirt, mildew, grayed wood, loose fibers and coating particles in one step.

Weathering or Seasoning. Most new treated wood decks should be protected with a water repellent, toner or semi-transparent stain as soon after construction as possible. Research shows that exposing unprotected wood to weathering for even short periods of time can cause surface damage, reducing the wood's ability to hold onto subsequently applied coatings. Unless treated wood is still very wet, coat it as soon as possible after construction.

Color Bleed-through. As a reaction to CCA, wood takes on a color of anywhere from a light brown to a bluish-green. Since wood is tremendously variable, the color of treated wood can vary significantly from board to board, even within the same board. Clear or lightly pigmented finishes do little to mask or even out the color; the CCA green may show through. Use darker colors, more opaque finishes or a second coat.

Over-application. Many d-i-yers and contractors believe that when it comes to coating, more is better. This is untrue-and a problem for decks. Most deck finishes are designed to penetrate the wood surface. Applying too much may build up a film that can peel or crack. For water repellent products, over-application can create a surface that is waxy, sticky or slick. Over-applied stains can result in sticky surfaces, because the coating build-up interferes with proper drying.

Unlike most other preservatives, ccA does not adversely affect wood finishes.

Horizontal vs. Vertical. Solid color stains and paints can be used successfully on vertical surfaces such as siding, trim and lattice. Yet most treated wood in home construction goes into decks. Paints, varnishes, and solid color stains usually are not recommended for exposed horizontal deck surfaces, treated or untreated.

Follow the manufacturer's label suggestions on coverage. Rough sawn surfaces can absorb more coating than smooth sawn substrates. However, since most CCA treated wood has a smooth surface, take particular care against applying too much material. One coat is sufficient for most deck finishes. If two coats are desired, be sure the first coat properly penetrates the surface before applying a top coat.