Wood is not the only material used for decks, but it remains the most popular decking material. In parts of the country where they are available, redwood and cedar are the top decking choices, while exotic species -- primarily ipé -- are durable, attractive and somewhat pricey alternatives. When it comes to posts, joists and other structural parts of the deck, builders tend to use pressure-treated softwood because it is long-lasting, even in extreme weather situations. It can be in ground contact, and it doesn't break the bank.
Redwood Vs. Cedar
Both redwood and cedar contain natural oils and tannins that resist rot and fungal growth, and both are equally durable -- although redwood is slightly harder and smoother. Choosing between them comes down to color preference, budget and availability. Redwood is naturally reddish in color, while cedar -- even western red cedar -- is more yellowish. Because redwood grows on the west coast, it tends to be less expensive in the western states than elsewhere. The nationwide supply of cedar, on the other hand, is larger, so it costs about the same in California as it does in Texas or New York.
Lumberyards grade boards according the the number of knots and defects, and the finest grades, which are blemish-free, are usually prohibitively expensive. You don't need these unless you're constructing a top-grade deck, however. When it comes to redwood, construction heart -- or con heart -- and deck heart boards are affordable and suitable for most purposes. The difference between them is that deck heart boards are graded more for durability than appearance. They are mostly heartwood, which is harder and more stable than sapwood, and though they may have knots, they display the deep red tones that are characteristic of this attractive species.
Trees that grow in the tropics yield hard, oily lumber, and producers farm some species for export. The lumber is durable, rot-resistant and makes for luxurious decking material. Tigerwood boasts dramatic streaks of contrasting colors while cumaru and Philippine mahogany have a deep, rich grain, but the best-known and most widely available species is ipé, also known as Brazilian walnut or lapacho.
Ipé boards are knot-free and vary in color from deep brown to golden yellow, taking on a reddish tone when finished with oil or varnish. The wood is one of the hardest in the world, with a Janka hardness rating around 3,600, about three times that of white oak. The wood is difficult to work, and must be pre-drilled before being screwed down. The extra effort is worth it, though, because an ipé deck is long-lasting and attractive.
Pressure-Treated Fir and Pine
Infusing wood with a preservative such as Alkaline Copper Quaternary (ACQ), Copper Azole (CA) or Micronized Copper Azole (MCA) under pressure produces a fungus- and pest-resistant building material that can remain in ground contact without rotting. It is suitable for deck posts, beams, joints and, in places where redwood and cedar are prohibitively expensive, decking boards. Softwoods such as southern pine and Douglas fir are the most common pressure-treated species because they are porous enough to allow the preservative to penetrate. They are also abundant, making pressure-treated wood as economical as it is durable. The preservatives give pressure-treated wood a reddish-brown hue that is a good match with natural cedar or redwood. It doesn't need a finish, but it can be painted to match the color of a house or to blend with the surroundings.
Finishing Decking Wood
All wood species, whether rot-resistant or not, last longer when you coat them with a clear, semi-transparent or opaque finish. A pigmented finish deflects ultraviolet sunlight and prevents redwood and cedar decking boards from turning gray and ultimately cracking. A deck in the shade, on the other hand., benefits from a clear, water-resistant coating to curb deterioration from rot and fungus, which happens eventually to all wood subjected to persistently moist conditions.
When constructing a new deck, it's important to allow it to weather for six weeks to two months before applying a finish. New wood is often wet, and coating wet wood locks in the moisture, which can result in warping wood and flaking finish. Most water- and oil-based finishes work equally well on redwood and cedar boards, but if you make your deck from ipé or another exotic hardwood, use a penetrating oil. Film coatings quickly flake off dense hardwood boards, whereas oils soak in to protect the grain and giving the surface a lush, luminescent shine.