Composite decking: what to know before you choose

Three kinds of board sold as composite

Stores put all of these on the same shelf. They are built differently, and the difference shows up in weight, heat and price.

• Capped composite: wood fiber and plastic in the core, a plastic shell over itTrex, most TimberTech lines, Fiberon Concordia, Sanctuary and Good Life, Eva-Last Infinity. The shell is what keeps water, stains and sun out of the core. Old uncapped boards were the ones that went moldy and faded, and they are the reason composite once had a bad name.
• PVC: no wood fiber at allTimberTech Advanced PVC (sold for years as AZEK), Fiberon Promenade and Paramount, and Eva-Last Apex Plus and Pioneer, which are PVC reinforced with glass fiber. Lighter than composite and indifferent to water. Usually the most expensive tier.
• Mineral-based composite: minerals in the core instead of wood fiberDeckorators Voyage and Summit. Deckorators says the mineral core keeps the board more stable through temperature swings, which matters on long straight runs.
• Redwood, for comparison: real woodCheaper to build, and nothing else looks quite like it. It asks for sanding and stain on a schedule. Skip that and it turns grey.

Composite deck cost next to wood

Per square foot, built, for a new deck on level ground. Straight from our calculator.

Replacing an old deck adds about $5 per sq ft for taking the old deck down ($2 in redwood); hauling it away is quoted separately. Elevated decks, 5 ft and up, add $5 to $10 per sq ft, hillside decks run about 22% more, multi-level about 15%.

The boards we install, and what the manufacturer warrants

These are the lines that show up in our estimates. The warranty terms are the manufacturers', taken from their own documents. We add our own three-year warranty on the workmanship.

Where composite decks go wrong

Each of these is written into the manufacturer's install guide, and the board warranty is written against that guide.

• Joist spacing for composite decking: 16 inches, 12 on a diagonalTrex puts joists at 16 inches on center for a normal layout and 12 inches when the boards run diagonally. A frame laid out for 2-inch wood decking at 24 inches will feel springy under composite boards.
• Gaps set by temperature, not by eyeComposite grows in heat and shrinks in cold. Trex asks for 1/4 inch between boards and 1/8 inch at the ends when the boards go down above 40°F. Too tight and the deck buckles in August. Too loose and the ends open up in January.
• The brand's own clips and screwsEach system is tested with its own hidden fasteners, and the manufacturer's install guide is what the warranty is written against. Mixing brands is the easy way to lose that.
• A border that is framed forA picture-frame border looks finished, but it needs extra blocking under it. It has to be planned in the framing, not added at the end.

Our take on the brands

• Eva-Last: stiffer boards, the most natural grainEva-Last reinforces Apex Plus and Pioneer with glass fiber inside the board, and Infinity IS uses an I-beam profile. Underfoot that reads as a stiffer board than most. To our eye its grain is also the closest to real wood of any brand we install.
• Less slippery in fog and drizzleCoastal and Peninsula mornings keep a deck damp for hours. In our experience Eva-Last and Deckorators Summit and Voyage keep their grip better in that weather than the other brands we install.

Composite decking colors: our advice

• Light boards over cool-touch linesHeat-reducing lines cost more. In our experience a light color gets you most of the way: it heats up less in the sun, and it costs less.
• Light colors fade less visiblyEvery manufacturer promises a long fade warranty, and over enough years every board still fades a little. On a light board you hardly see it. On a dark one you do.
• Light boards hide dustDust and pollen show far less on a light deck, so it needs washing less often.
• Look first, heat secondIf you walk the deck in sandals, board temperature hardly matters. Most people go barefoot on it now and then, and look at it every day, so we would choose the color you like to look at.

If your house is in a fire zone

In a mapped fire hazard zone the building department asks for decking that the California State Fire Marshal has listed for wildland-urban interface (WUI) use. Check the listing before you order, not after.

• TimberTech is the strongest hereTimberTech lists its Advanced PVC Vintage, Landmark and Harvest+ collections with a Class A flame spread rating and as WUI compliant, and Harvest, Reserve and Premier as WUI compliant. That fire rating is part of why those lines cost more. Prime+ is not on that list.
• Fiberon PVCFiberon rates Promenade and Paramount Class A. For a fire-zone deck, confirm the exact line in Fiberon's fire-rated decking guide.
• Eva-Last Apex is on the state listEva-Last's Apex boards are on the State Fire Marshal's list of decking approved for fire zones (listing 8110-2314:0500), installed with the Hulk hidden fastener system as the listing describes. Eva-Last plans the same for Pioneer and possibly Infinity.

What deck owners run into

We read what owners write on deck forums after a few years with their boards. These came up more than once.

• The line matters more than the brandEvery big brand sells an entry line and a top line. Scratch and dent complaints cluster on the cheaper lines, whatever the logo.
• Grills leave marksHot oil, ash or a dropped grill tool can melt a spot into the surface. Put a heat mat under the grill.
• Windows can burn a deckSunlight reflected off low-E windows can discolor or warp composite and PVC near the house. TimberTech and Eva-Last both exclude that damage from their warranties, so a board under a south-facing window is worth a second look.
• Wet boards get slickOwners of capped composite and PVC mention slipping after rain. Mineral-based boards come up again and again as the grippier choice.
• Online prices run lowThe number that surprises people is not the boards. Framing, fascia, stairs and taking out the old deck are where a quote grows.

Questions people actually ask