Composite Decking in Kent, WA
Capped composite and PVC boards for owners who want the deck to look the same in year fifteen as in year one, without a stain schedule. What it costs here, where it shines, and where it still needs help.
Composite Against Cedar in a Kent Winter
The question behind most composite quotes in Kent is whether the extra cost buys anything a cedar deck with a good stain schedule would not.
Composite decking in Kent costs about $45 to $75 per square foot installed, roughly $10 to $20 more than cedar, and earns it back by skipping the reseal cedar needs every two years in 40 inches of rain. Moss still grows on it in shade but rinses off.
The lifespan gap is the other half of the case. Regional builders put cedar at 15 to 25 years with maintenance and capped composite at 20 to 30 or more, with PVC beyond that. Composite does not absorb water, so it does not swell, check, or rot at the end grain, and there is nothing in it for a carpenter ant to eat. What it does not do is protect the frame under it: the joists and ledger are still pressure-treated wood, and a composite deck on a wet, untaped frame fails from underneath on the same schedule as any other.
Which Boards, and What They Cost
Capped composite
Trex and TimberTech's composite lines are a wood-flour and plastic core wrapped in a hard polymer cap. The cap is what resists staining and fading; the core is what gives the board its weight and stiffness. Board cost alone runs about $6 to $12 per square foot, and installed prices in the south King County market land around $45 to $75 once framing, fasteners, and labor are in. This is the board most Kent owners end up with.
PVC
All-plastic boards, TimberTech's Azek line among them, have no wood in the core at all. They are lighter, cost more, and are the pick for a deck that stays wet year-round: a north-facing deck under trees, a deck over a living space, or one at the lake. Installed cost runs about $50 to $85 per square foot.
Cedar, for comparison
About $35 to $60 installed, a reseal every two years or so at a few hundred dollars each time if you do it yourself and more if you hire it, and the best-looking board on the market on the day it goes in. Owners who like the maintenance rhythm and the smell keep choosing it. The cost guide lays the three side by side over twenty years.
What Composite Needs From the Frame
- Tighter joist spacing. Composite flexes more than cedar between supports; manufacturers call for joists at 16 inches on center for straight runs and 12 inches for diagonal patterns. An old 24-inch frame cannot take it without sistering.
- Joist tape and ventilation. Because the boards last longer, the frame has to last as long. Tape over every joist top and a real air gap under the deck are standard on a composite build here.
- Room to move. Composite expands and contracts with temperature more than wood, so end gaps and side gaps follow the manufacturer's chart rather than the carpenter's habit. Gaps closed up tight in July buckle in January.
- The right fasteners. Hidden clips in the board groove or color-matched screws made for the product; ordinary deck screws mushroom the cap.
- Color and heat. Dark boards absorb sun and get hot underfoot on an exposed south deck in August. Lighter greys and browns run cooler and hide pollen and fir needles better in a Kent spring.