Seattle gets roughly 150 rainy days a year, and even in the dry months, morning dew and shade from mature trees keep a lot of decks damp far more often than a spec sheet would suggest. That reality should drive the wood-vs-composite decision more than looks or upfront price alone.
Wood decking
Cedar
The regional default, and for good reason — western red cedar has natural oils that resist rot and insects, and it's grown locally, which keeps cost and embodied carbon down compared to shipped-in species. It will silver over time unless you commit to annual or biannual oiling. Expect a well-maintained cedar deck to last 15–20 years; neglected, closer to 10–12 before boards need replacing.
Pressure-treated lumber
The budget option. Chemically treated to resist rot, it holds up reasonably well here but tends to warp and check (crack) as it dries and wets repeatedly through our seasons. It's a reasonable choice for a structural substructure even if you choose a different decking material for the surface.
Ipe and other tropical hardwoods
Extremely dense and rot-resistant — genuinely the longest-lasting wood option, 25+ years with minimal maintenance. The tradeoffs are cost (often 2–3x cedar), weight, and sourcing concerns worth asking your contractor about (look for FSC-certified sourcing).
Composite decking
Composite (wood fiber + plastic, capped with a protective shell on higher-end products) has gotten genuinely good over the last decade, and it solves the specific problem our climate creates: it doesn't rot, doesn't need annual staining, and resists the moss and algae growth that's a constant fight on shaded PNW wood decks.
The tradeoffs:
- Upfront cost runs higher than cedar, though it usually wins on lifetime cost once you account for cedar's recurring maintenance.
- Heat isn't the issue here it is in sunnier climates, but darker composite boards can still get noticeably warm on the rare hot summer day.
- Look has improved a lot, but some homeowners still find it reads as slightly less warm than real wood grain, especially up close.
The moss problem is real either way
In shaded, damp spots — common under mature PNW tree canopy — both wood and composite decks will grow moss and algae if they don't get some sun and airflow. Composite is easier to clean (pressure wash + deck cleaner), but neither material is maintenance-free in full shade.
So which one actually holds up?
For most Seattle-area homeowners, the honest answer depends on how much annual maintenance you're realistically going to do:
- Will actually oil/stain annually? Cedar gives you real wood character at a lower upfront cost and ages beautifully if maintained.
- Want to install it and mostly forget about it? Composite is the better bet — the higher upfront cost buys back a lot of weekend time over 20 years.
- Building in a shaded, damp spot? Either material needs airflow and occasional cleaning; consider whether some canopy trimming is part of the project.
A note on substructure
Whichever surface material you choose, the framing underneath matters just as much in our climate. Ask your contractor about proper drainage slope, joist tape or flashing to protect pressure-treated framing, and ventilation underneath the deck — standing moisture under a deck is one of the most common causes of early failure here, regardless of what's on top.
Next steps
Once you've picked a material, our cost guide and budget estimator can help you scope the project, or browse design-build firms who work with both materials regularly.
