Selecting Finishes for a Deck or Porch

Intro

Finishes do more than make the wood look good. The right finish will protect your deck and help it seem a natural extension of your landscape design.

When you're out shopping for deck finishes, or while you're still in the early planning stages, think first about the color you want -- for example, brown, red, or green. Then consider what shade of that color your deck should be -- dark brown, tan, pale red, or dark green. Then give some thought to what sheen (flat or glossy) will look best. Decks generally look best with a flat sheen, but a contemporary design scheme might call for something different from the norm.

Then look for information that tells you how durable the finish is and how easy it will be to apply. Generally sealers are the easiest to apply, followed by stains, with paint taking the most time and effort. Consider the species of the wood too. A clear finish is a good choice for redwood and cedar. It allows their natural colors to show through. Pressure-treated lumber usually requires staining or painting.

All finishes will alter the appearance of all woods. The photos on the following slides give some idea of the range of appearances different finishes will effect on the same wood (here, untreated Douglas fir). The colors and tones shown in the photos are only representative of degrees of change. Different brands and changes in the wood grain, even within the same board, produce different results.

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The weathered look

If you like wood with a gray, weathered look, don't finish, seal, or paint the deck. Let nature weather the wood naturally. Natural weathering works best with all-heartwood grades of durable species, such as cedar, cypress, and redwood.

The aging time varies with the species and its exposure. Generally cedar and cypress weather to a light silver-gray and redwood turns dark gray. Pressure-treated lumber turns a soft gray but sometimes retains a hint of its green or brown coloring.

What will it look like? Oil-base clear sealer

Sealer
Clear or lightly pigmented sealers protect the wood from water damage and don't change its color much. Look for additives that will ward off mildew, insects, and fungi. Ultraviolet (UV) blockers are a must -- they reduce damage caused by the sun's rays. Pigmented sealers do all of the above, but the pigment is designed to change the color of the wood slightly.

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Enough sealant?

Is your deck sealed properly? In some cases the answer is obvious. Old wood with a dried-out look clearly needs a stiff dose of sealer. But boards that look OK may also be in danger of drying out. So do a quick test once or twice a year. Sprinkle a little water onto the surface. If the water beads up and does not soak in within two minutes, the board is sealed well enough. If water soaks in within 2 minutes, apply additional sealer.

What will it look like? Latex clear sealer

All-purpose sealers contain water repellents, preservatives, and UV blockers. You can apply sealers over or under stains and under primer and paint.

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What will it look like? Semitransparent stain

Stain
Stains are primarily formulated to transform the appearance of the wood -- some slightly, some dramatically. Certain formulas are designed to offer some protection to the wood, but this is a job best done with a sealer in conjunction with a stain.

What kind of stain you use will depend on how much of the original wood tones you want to retain. Semitransparent stains allow more wood grain to show through but wear away more quickly; they are particularly suitable for highlighting wood grains.

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Different Finishes: Sample finishes first

Before applying any finish -- staining or painting especially -- you'll want to know how the final color will look. The only way to really be sure is to see the color when the finish is dry.

Test the final color by applying a small amount in an out-of-the-way spot on your deck. Let the finish dry to make sure it produces the color you want. Paint usually dries darker than when wet. Stains usually dry lighter.

What will it look like? Heavy-bodied stain

Heavy-bodied stains contain more pigments and hide the grain. All stains (both oil- or water-base products), including those not designed to penetrate the fibers of the wood, tend to retain the wood's natural look far more than paint. Apply oil-base stains on redwood and red cedar.

Stains are somewhat less expensive than paints, take less time to apply, and go on easily over rough and smooth surfaces.

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What will it look like? Paint

Paint
Paints conceal some defects and tend to last longer and look better than stains on smooth surfaces. Exterior alkyds (oil-base products) are more costly, more difficult to clean up, and slower-drying. Water-base latex paints cost less, clean up easily, and dry quickly. Each comes in a range of colors and sheens (gloss, semigloss, and flat or matte). New, unpainted surfaces need to be primed first. Oil-base primers provide better protection on raw wood than water-base primers. Add stain blockers to stop bleed-through from redwood and cedar. A good-quality acrylic-latex top coat applied over an alkyd primer makes a durable finish.

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What If... You want to lighten the wood?

Bleaching agents change the appearance of wood by altering the chemical composition of the surface fibers. They offer a way to tone down the jarring look of a brand-new deck. They soften the raw-wood look and help the varying shades of natural wood to blend in. You get the effect of two seasons of natural weathering in one application, because like the sun, the treatments strip color from the wood fibers. Sealers stop the bleach from working, so if you plan to bleach the wood, don't seal it first. Wait two months after applying the bleach to seal the wood.