Trex Decking 20 Ft Boards: Real Prices and When They Are Worth It

Trex 20 ft deck boards are the longest standard length the company sells, and they exist for one reason: to let a board run the full width of a typical residential deck without a seam. That matters more than it sounds – fewer seams means fewer places for water and grit to collect, fewer fasteners to install, and a cleaner sightline down the deck.

Trex sells composite decking in 12, 16, and 20 ft lengths, and not every product line stocks all three. Below is what the 20 ft option actually costs, how it differs physically from the shorter boards, and the fasteners and screws you will actually need to put it down correctly.

Trex Decking 20 Ft: Real Prices and Board Specs

At major retailers, a single Trex 20 ft board typically runs about $46.78 to $51.98, which works out to roughly $5.10 to $5.67 per square foot of decking before labor. Buying in bulk (56 boards or more) usually drops the per-board price toward the low end of that range – worth asking about if you are decking an entire backyard rather than a small landing.

Board thickness varies by product line, and this is the detail most buying guides skip:

Trex Line	Board Thickness	Board Width	20 Ft Available?
Trex Select	0.82 in	5.5 in	Yes
Trex Enhance	0.94 in	5.5 in	Yes
Trex Transcend	0.94 in	5.5 in	Yes

The Enhance and Transcend lines are about 15% thicker than Select, which translates to a slightly stiffer board over long joist spans – relevant on a 20 ft run where mid-span deflection is more noticeable than it is on a 12 ft board. You will also choose between a grooved edge (accepts hidden fasteners, no visible screw heads) and a square edge (face-screwed, cheaper hardware, visible fastener heads). Most 20 ft installs use grooved boards specifically so the long, uninterrupted run does not show a line of screw heads down its length.

Why Choose the 20 Ft Length at All

Trex Decking is a wood-alternative composite made from a blend of reclaimed wood fiber and recycled plastic film (much of it originally grocery and shrink-wrap film). It will not splinter, does not need annual staining, and carries a 25-year fade and stain warranty on most product lines. None of that is unique to the 20 ft length – you get it with the 12 ft boards too. What the 20 ft length adds is purely about layout:

• Fewer seams: a 20-ft-wide or 20-ft-deep deck can be covered in one continuous run instead of two 10 ft boards butted together.
• Less waste: cutting a 16 ft board down to fit a 15 ft span wastes a foot of material every row; a 20 ft board gives you more room to plan cuts around a full deck’s dimensions.
• Fewer joist-line fasteners: every butt joint needs its own blocking and fastener row underneath it. Skipping a joint on a long run means skipping that extra hardware and labor.

The tradeoff is handling and shipping: a 20 ft composite board weighs roughly 45-55 lbs depending on the line, and it needs two people (or a long truck bed) to move without flexing and cracking it. If your deck’s longest run is under 16 ft, the 20 ft board buys you nothing but a harder delivery.

Trex 20 Ft vs. Traditional Wood Decking

Feature	Trex Composite	Pressure-Treated Wood
Expected lifespan	25-30 years	10-15 years
Annual maintenance	Occasional wash	Sanding/staining every 1-2 years
Material cost per board (20 ft)	~$47-$52	~$25-$35
Longest standard length	20 ft	Typically 16 ft (special order for longer)

Wood wins on upfront material cost. Trex wins on total cost of ownership once you factor in the stain and sealant a wood deck needs every one to two years, plus the labor to apply it. For a deck you plan to keep for 20+ years, the composite premium is usually paid back within the first decade in avoided maintenance alone.

Installing 20 Ft Boards: Joist Spacing and Fasteners

The extra length changes two things about installation: joist spacing tolerance gets tighter, and you need a fastening plan that will not telegraph screw heads down a 20 ft run.

Joist Spacing	Recommended For
12 in on-center	Diagonal installs, or boards laid at an angle to the joists
16 in on-center	Standard residential decking, most 20 ft runs

Trex specifies 16-inch on-center joist spacing for standard perpendicular installs; tighter 12-inch spacing is required if boards run diagonally. On a 20 ft board, that means roughly 15-16 joists supporting a single length of decking – miss the spacing tolerance and you will get noticeable bounce closer to mid-span than you would on a shorter board.

For fasteners, grooved 20 ft boards take hidden composite clips that lock into the groove and get screwed down into the joist below – no face screws, no visible hardware. Square-edge boards get face-screwed with a corrosion-resistant, composite-rated deck screw (standard wood screws can react with the composite’s moisture content over time and streak the board). Pre-drilling is not usually required with the right composite screw, but always start screws at least an inch from a board’s end to avoid splitting.

Ground prep matters just as much as the boards themselves: clear the area, grade for drainage away from the house, compact the base, and lay a weed barrier before framing. Check your local building code before you start – some jurisdictions require a permit and inspection for any deck attached to the house, regardless of decking material.

Color and Finish Options

Color availability can vary by length and product line – always confirm a specific shade ships in 20 ft before you design around it, since some limited-run colors are only stocked in 12 and 16 ft. Popular options across the Trex lineup include:

• Gravel Path – a cool gray that reads modern against light-colored siding.
• Havana Gold – a warm brown that mimics tropical hardwood.
• Beach Dune – a light tan that stays cooler underfoot in direct sun.

All current Trex lines use a cap-stock (a protective outer shell fused to the composite core) that handles UV exposure and fading better than the uncapped composite boards sold a decade ago. That shell is also what makes the boards resist the grocery-bag-plastic streaking older composite decking was known for.

Maintenance: What a Trex Deck Actually Needs

Routine care is genuinely minimal: sweep off debris, and wash with warm water, mild soap, and a soft-bristle brush a couple of times a year. Rinse thoroughly and let it dry. For mildew or ground-in dirt, a dedicated composite deck cleaner outperforms a pressure washer used alone – and if you do pressure wash, keep the nozzle on a wide fan setting and at least 8 inches from the board to avoid gouging the cap-stock shell.

Scuffs and light scratches on capped boards can often be buffed out with a Trex-branded touch-up kit or a heat gun on a low setting (test on a scrap piece first). Deep gouges that go through the cap-stock into the composite core are not repairable the same way – at that point the board section needs to be replaced, which is one more argument for keeping a couple of spare boards from the original order.

Frequently Asked Questions

What is Trex decking made of?

Trex composite decking is made from a blend of reclaimed wood fiber and recycled plastic film, sealed under a protective cap-stock shell. It will not splinter or rot the way solid wood can, and it does not require staining or sealing.

How much does a Trex 20 ft board cost?

A single Trex 20 ft board typically costs $46.78 to $51.98 at major home improvement retailers, or roughly $5.10 to $5.67 per square foot before installation. Buying 56 or more boards at once usually brings the per-board price down toward the lower end of that range.

Is it hard to install 20 ft Trex boards?

Installation uses the same tools and techniques as any composite deck, but the extra length means you will want a second person to carry and align each board, plus careful joist spacing (16 inches on-center for standard installs) since a long board shows mid-span bounce more readily if spacing is off.

How long does Trex decking last?

Most Trex product lines carry a 25-year fade, stain, and structural warranty, and boards commonly stay in service 25-30 years with basic seasonal cleaning. That compares with roughly 10-15 years for pressure-treated wood before boards typically need replacement.

Conclusion

A 20 ft Trex board is worth the extra handling and delivery hassle specifically when your deck’s longest run is close to that length – it eliminates a seam, a joint’s worth of fasteners, and a visible break in the boards. If your deck’s longest dimension is under 16 ft, a shorter board will cost less to ship and be just as easy to work with. Either way, confirm your color and product line actually stock the 20 ft length before you order, and budget for composite-rated screws or hidden fasteners rather than standard wood hardware.