What type of wood is best for decks in Oregon?

For the frame, pressure-treated lumber treated for how it is used, since the posts, beams and joists hold the deck up. For the boards, pressure-treated wood is the lower-cost choice, and cedar costs more but resists decay. OSU Extension notes that in Western states such as Oregon, Douglas-fir is most often treated with CA-C or ACQ preservatives.

Is composite decking better than wood in a wet climate?

It depends on what you want to spend and maintain. Composite and PVC boards are made largely or entirely of plastic and come with long manufacturer warranties; composite cost more than wood for the same deck in the 2024 Portland figures. Either way the boards sit on a frame that has to stay sound, and moss can grow on any shady deck.

Best Decking Material for Portland's Wet Climate, Compared

Short answer: in Portland, choose the frame for rot resistance first and the boards for the upkeep and price you want. Pressure-treated wood is the lowest-cost deck. Cedar costs more and resists decay. Composite and PVC boards are plastic-based and carry long manufacturer warranties, and composite costs more than wood for the same deck. Whatever you choose, moss can grow on a shady deck, so plan to clean it.

Why Portland is hard on decks

Rain is the main reason. The 1991-2020 climate normal at Portland International Airport is 36.92 inches of precipitation a year (NOAA), and east and south of the city it is wetter: 40.66 inches at Troutdale and 44.81 inches at Oregon City. Oregon State University Extension notes that wood that stays wet from rain and irrigation decays faster, and that moist, shady spots are ideal for moss, which it warns can make decks slippery. A deck in deep shade, on the north side of a house or close to damp ground is the most exposed to both.

Pressure-treated wood

Pressure-treated lumber is wood treated with preservative to resist decay. OSU Extension lists copper azole (CA-C), micronized copper azole (MCA) and alkaline copper quaternary (ACQ) as the most common preservatives for lumber, and notes that CA-C and ACQ are more commonly used in Western states such as Oregon to treat Douglas-fir. For anything in or near the soil, it advises making sure the lumber is treated for “ground contact”.

It is the lowest-cost deck of those with published Portland prices: in the 2024 figures from the Cost vs. Value Report, the same deck cost less in wood than in composite.

Treated wood is also what holds up many composite decks. The report’s composite project, for instance, uses pressure-treated joists on 4x4 posts anchored to concrete piers.

Cedar

OSU Extension notes that redwood and cedar “are more expensive but resist decay, so they last longer.” The durability is in the heartwood: the American Wood Council’s deck construction guide counts Western cedars as naturally durable only where 90 percent or more of the width of each side is heartwood. Ask what grade of cedar a quote is for.

Tropical hardwood

Ipê and similar hardwoods are dense, durable boards. A USDA Forest Service study describes ipê as “extremely durable in exterior conditions because of its resistance to microbial and insect degradation.” If you are considering it, ask the contractor whether they install it.

Composite and capped composite

Composite boards blend plastic and wood fiber. TimberTech describes its composite as “a blend of virgin and recycled polymers, along with organic material like wood flour”; Trex says its composite uses “95% recycled plastic film and reclaimed sawdust.” Capped composite adds a protective outer shell: TimberTech’s composite collections have a three- or four-sided cap.

Warranties are long and vary by line. On the makers’ sites in October 2026, Trex listed 25- to 50-year limited residential warranties across its decking, and TimberTech 25 to 30 years for its composite collections, with fade and stain warranties of the same length. See composite deck builders for what changes when a deck is built with composite.

PVC

PVC boards contain no wood. TimberTech says its Advanced PVC is “engineered from recycled material — with zero wood or organic fillers” with “a four-sided protective cap”, and lists a limited lifetime product warranty with a 50-year fade and stain warranty. Fiberon lists lifetime and 50-year warranties on its PVC lines.

Side by side

Material	What it is	Rot resistance	Price	Board warranty
Pressure-treated wood	Treated lumber; in Oregon, commonly Douglas-fir treated with CA-C or ACQ (OSU)	Treated to resist decay; use ground-contact lumber near soil	Lowest with a published Portland price (2024)	None from a decking brand
Cedar	Western cedar	Resists decay (OSU); heartwood is the durable part (AWC)	More than treated wood (OSU)	None from a decking brand
Tropical hardwood	Ipê and similar	“Extremely durable” (USDA Forest Service)	No published Portland price	None from a decking brand
Composite	Plastic blended with wood flour or sawdust, often capped	Depends on the product; read the warranty	More than wood for the same deck (2024)	25 to 50 years, by line
PVC	Plastic with no wood or organic fillers	Depends on the product; read the warranty	No published Portland price	Lifetime or 50 years, by line

Moss and maintenance

Whatever the boards, a Portland deck needs cleaning. Oregon State University names pressure washing as effective for decks, patios and sidewalks, and notes that a moss killer kills moss but you still have to remove the dead material. Because moist, shady spots suit moss best, more light and better drainage work against it.

If your current deck is already soft, split or slippery, start with deck repair and replacement. For prices, see what a deck costs.

This page is general information, not professional advice about your specific situation. Have it assessed by a qualified professional before making decisions. Last reviewed October 9, 2026.