How to Tell the Difference Between Composite and PVC Decking

You walk into the lumberyard, point at a board, and ask what it is. Half the time the guy behind the counter doesn’t know either. “Composite” and “PVC” get thrown around like they mean the same thing. They don’t.

Here’s the short version. Composite decking has wood in it. PVC decking has none. Everything else — the weight, the feel, the heat, the way it moves in the sun — comes down to that one difference.

Let me walk you through how to actually tell them apart when you’re standing in front of the board.

What each one actually is

Composite is a blend. Roughly half recycled wood fiber, half plastic — usually polyethylene — mixed together and extruded into a board. The newer stuff has a plastic cap on the outside to keep water and stains out, but underneath, it’s still part wood. That wood is why it looks more natural. It’s also why the cheaper, uncapped composite from twenty years ago rotted, molded, and turned into black mush on people’s back decks.

PVC has zero wood in it. It’s all polyvinyl chloride — the same family of plastic your plumbing lines are made from. That means no organic material for water to soak into, no fibers for mold to eat, and nothing that behaves like a tree ever did. It’s a plastic board pretending to be a plank.

Both look pretty good these days. That’s the problem. You can’t always tell by looking.

The weight test

Pick up the board. PVC is noticeably lighter. A full-size composite plank in your hand feels like a piece of lumber — dense, solid, has some heft to it. PVC in the same length feels hollow even when it isn’t. If you’re standing there flipping between two boards and one feels like a two-by-six and the other feels like a pool noodle in comparison, that’s your first tell.

Weight also matters when you’re building. PVC is easier to carry across a job site and easier on your framing. Composite’s heavier boards need more support underneath — pay attention to joist spacing in the manufacturer’s spec, because “16 inches on center” is not universal.

The feel

Run your hand across the surface. Composite has a bit of texture, sometimes a wire-brushed or scraped grain pattern. It feels like something that used to be a tree. PVC feels slick. Even when it’s got a wood-grain print stamped into it, the surface has that plastic quality — a little too smooth, a little too uniform. Once you’ve felt both back to back, you don’t forget.

Look at a cut end if the store will let you. Composite will show a solid, sometimes speckled cross-section where you can see wood fiber mixed in. PVC is uniform all the way through, or foamed with tiny air bubbles you can see if you look close. That’s the dead giveaway. No wood in there, none coming out.

Heat in the sun

Both of them get hot. Anybody who tells you different is selling something. Dark colors on either material will cook your feet in July. That said, PVC generally runs a few degrees cooler than composite in direct sun because the surface reflects more heat instead of holding it. If you’ve got a south-facing deck with no shade and small kids running around barefoot, that difference matters. Go with a light color regardless of which material you pick — that helps more than the material choice does.

I had a customer in South Philly convinced her dark composite deck was defective because the boards were “too hot to walk on.” It wasn’t defective. It was black plastic on a rowhouse roof in August. She wanted me to come tear it out. I told her to buy an outdoor rug and thank me later.

How they move

This is the one homeowners miss. Both materials expand and contract with temperature, but PVC moves more. Longer boards in direct sun can grow a quarter inch or more between morning and afternoon. If your installer didn’t leave the proper gap at the butt joints — and I mean the exact gap the manufacturer calls for, not “eyeballed it” — the boards will push against each other, buckle, or pop the hidden fasteners loose.

Composite moves too, just less dramatically. Either way, follow the install guide. Every manufacturer publishes one, and every homeowner who ignored it ended up calling somebody like me to fix it.

The brand trap

Now here’s where it gets messy. People assume the brand tells you the material. It doesn’t.

Trex is composite. Always has been. TimberTech has both — their PRO line is composite, their AZEK line is straight PVC. Fiberon runs multiple lines, and some of their higher-end products are pure PVC while their more affordable lines are composite. Deckorators has a mineral-based composite that’s a whole other animal — different weight, different feel, doesn’t fit neatly into either camp.

Don’t shop by brand name. Read the actual product spec sheet. The material is listed on it. If the sheet doesn’t say clearly what the board is made of, walk away. Any manufacturer worth your money will tell you exactly what’s in the product.

Which one should you pick?

Depends on what you want.

  • If you want the most natural wood look and don’t mind a little more weight, go composite.
  • If you want the lightest, longest-lasting, mold-proof board and you can live with a slightly plastic feel, go PVC.
  • If your deck is over water, over a pool, or somewhere it stays wet for weeks at a time, PVC has the edge. No wood fiber, no problem.
  • If you’re on a budget, capped composite from a reputable manufacturer will do the job for most homeowners.

Either one, if you buy the good stuff and install it right, will last longer than your current mortgage. Buy the cheap stuff, or hand it to a crew that doesn’t read the install guide, and you’ll be looking at a mess in five years.

Pick the board. Read the spec sheet. Follow the install manual. That’s it.