Is Composite Decking Worth It in the Pacific Northwest? Answers to Common Questions from a Seattle TrexPro® Installer

Composite decking comes up in a lot of our conversations with Seattle homeowners, often right after someone has spent another spring pressure washing and re-staining a cedar deck. We install Trex decking as a TrexPro® Certified Installer, and some of our team recently spent time at Trex’s facility in Virginia learning how the boards are made. Along the way, we have heard the same handful of questions again and again. Here are our honest answers.

Does composite decking get hotter than cedar?

Generally, yes, a bit. Composite is denser than cedar and tends to hold more heat in direct sun. That said, color plays a big role. Darker boards absorb more heat than lighter ones, which is true of almost any outdoor surface.

Trex has also been working on this problem directly. Its Lineage line uses heat-mitigating technology meant to reduce surface temperature buildup compared to traditional composite boards. Trex groups its lower-heat options under a “Sun Comfortable” filter, which you can browse on their color page.

If you want to see real numbers, a deck builder in South Australia ran a side-by-side heat test under identical sun conditions. Their Trex Lineage boards measured between 56°C and 59°C (about 133°F to 138°F), which was right in line with or cooler than several common hardwoods they tested. Some other composite brands in the same test ran as high as 72°C (about 162°F). They didn’t test cedar, and Adelaide sun is not Seattle sun, but it’s a useful reminder that not all composite performs the same.

For most Seattle decks, heat is a July and August consideration rather than a year-round one. If your deck faces south or west with no shade, it may be worth factoring color and product line into your decision.

Does composite expand and contract?

Not much on its own. Where we have seen problems, they come from installation rather than the material.

The most common issue is something called “skiing.” This is when the end of a board warps upward so it looks like the tip of a ski. It usually happens when boards are not installed with the correct fasteners or without a picture frame border.

With a picture frame installation, the field boards in the middle are fastened with hidden clips, and the edge boards around the perimeter are screwed down with squared ends. That border holds the board ends in place and gives the deck a clean, finished edge. It’s the approach we use on our composite installs.

Does composite decking fail?

We have not personally seen a composite deck surface fail, and we have not dealt with any material recalls on the products we install. Durability estimates for composite decking generally run 25 to 50 years.

The part that deserves more attention is what’s underneath. A composite surface is only as good as the frame it sits on. If the posts, beams, or joists are aging or damaged, new boards will not fix that.

This matters even more if you are replacing a wood deck surface with composite. Composite is significantly heavier than wood, so we need to confirm the existing posts and joists can support the added weight. We also look for ground slope issues or erosion around the footings before adding more load to the structure.

Am I limited in color selection?

Somewhat, but less than you might expect. Trex currently offers 32 colors across its decking lines, and the selection keeps growing. You won’t have the unlimited options of a stained wood deck, but there is a wide range of warm browns, grays, and wood-toned blends to choose from.

Does my deck qualify for composite?

That depends mostly on the substructure. When our estimators look at an existing deck, we check a few things:

• Joist spacing, which should be 16 inches or less
• The age and condition of the substructure
• Its current condition, including rot, sagging, or loose connections

If the frame is in good shape, you may be able to keep it and replace only the surface. If it isn’t, we will tell you, and we can talk through what a rebuild would look like. Our carpentry team handles both.

What railing options can I use?

Trex offers 12 railing systems, and aftermarket railings can be attached as well. Materials include aluminum, steel, vinyl, glass, cable, and wood. Here in the Pacific Northwest, aluminum, glass, and cable are popular choices because they keep views open, whether that’s the Sound, the mountains, or just your backyard.

What else can go with a composite deck?

If your deck is elevated, the space underneath is often wasted during our wet months. Trex’s RainEscape® under-deck drainage system diverts water away from the area below, so you can use it for storage, seating, or a covered hangout spot from fall through spring.

Once RainEscape is in place, you can finish the underside with tongue and groove ceiling boards for a cleaner look. Privacy screens and lattice work are other ways to round out the space.

So, is it worth it?

For many Seattle homeowners, yes. Composite does not need annual staining or sealing, holds up well in our rain, and gives you more years of use with less upkeep! It costs more up front than wood, and it isn’t the right fit for every deck, especially if the substructure needs significant work.

If you’re weighing your options, our estimator can come take a look and give you a straight answer on whether your deck is a good candidate. Reach out for a free quote or call us at (206) 258-6676.