The composite-versus-wood decision is usually framed as a price question, and priced only at the checkout it looks lopsided: pressure-treated lumber is far cheaper per board than composite. But a deck is a fifteen-to-thirty-year commitment, and the honest comparison runs over that whole life, including the weekends and dollars you spend maintaining it.
Upfront cost versus lifetime cost
Pressure-treated wood wins the sticker price and loses ground every year after. To stay sound and presentable it wants periodic cleaning, and depending on the look you want, sanding, staining, or sealing on a recurring cycle. That is material cost plus a meaningful amount of labor, yours or a contractor’s, repeated for the life of the deck. Composite costs two to three times as much up front but needs little more than washing. Whether it pays back depends on how long you keep the deck and how you value your own weekends; over a long horizon the gap narrows and can reverse, over a short one the treated wood stays cheaper.
Heat in direct sun
Both materials get hot in full sun, and the physics is about color and solar absorption, not the brand on the board. A surface warms in proportion to how much solar radiation it absorbs, which is driven mainly by how dark it is: a dark deck absorbs a large fraction of incoming sunlight and re-radiates it as heat, while a light one reflects more and stays cooler. The same effect makes dark urban surfaces dangerously hot; NASA’s thermal mapping of Phoenix streets, NASA’s ECOSTRESS burn-risk street mapping, shows how dark, sun-exposed surfaces reach temperatures far above the air. The barefoot-comfort lesson is to choose a lighter color and orient seating out of peak sun rather than to assume one decking material stays cool; a dark composite and a dark stained wood board in the same sun behave much alike. Sun-exposed surfaces can climb well past the threshold at which contact burns skin, a risk documented in clinical work on pavement and surface burns such as this study of contact burns from hot outdoor surfaces.
“Maintenance free” overstates it
Composite is low-maintenance, not no-maintenance. It does not need staining, but it stains: grease, tannins from leaves, and ground-in dirt mark it, and in damp, shaded conditions it grows mold and mildew on the surface film just as wood does. You still wash it, and neglected composite in a wet, shady spot can look worse than well-kept wood. The pitch of “maintenance free” oversells a real advantage.
What the treatment classes mean
Pressure-treated lumber is not one product; it is graded by use category, and using the wrong grade is a common and costly mistake. The treatment retention and category are matched to exposure, above ground, ground contact, or more severe, and a board rated for above-ground use will fail early if buried or set in soil. The industry’s consumer guidance, this American Wood Protection Association residential use category infographic, spells out which category goes where. Buy the category that matches the exposure, especially for posts and any wood touching the ground.
Most composites are not structural
One hard limit: the composite is a decking surface, not a beam. Most composite deck boards are not rated to serve as joists, beams, or posts, and they carry maximum span ratings between supports that are often tighter than wood. The frame underneath, the joists, beams, and posts, is still built from rated structural lumber or steel. Composite changes what you walk on, not what holds the deck up, so joist spacing has to follow the board manufacturer’s span table. Choose on lifetime cost, color for heat, correct treatment class for wood, and never confuse the surface for the structure.