Trex Decking Dimensions, Spacing & Hardware Guide: Board Sizes, Fasteners, Clips & Essential Accessories
Trex boards look simple, but the details under the surface are what make a deck last. Get the dimensions, the gaps, the joist spacing, and the hardware right, and the deck stays flat, even, and tight for decades. Get them wrong, and you risk buckling, sagging, trip points, or a voided warranty. This guide lays out the specs and hardware in plain language so you know exactly how the pieces fit together.
None of this is complicated once it is spelled out, and that is the goal here. Each number has a reason behind it, from the gap that lets a board breathe in the heat to the joist spacing that keeps the surface from bouncing. Understanding the why makes the specs easy to remember and easy to check.
Whether you are planning a build, checking a contractor’s work, or just want to understand what you are buying, here is everything about Trex board sizes, spacing, fasteners, clips, plugs, and the accessories that finish the job.
Trex Board Dimensions, Thickness, and Lengths
Trex keeps its sizing consistent across the lineup, which makes planning a deck much easier. Almost every board is the same width, so the main thing that changes between lines is the thickness.
Every Trex board is 5.5 inches wide across the Enhance, Select, Transcend, and Signature lines. The thickness is where the lines differ. Transcend and Enhance boards are 0.94 inches thick, while Select boards are thinner at 0.82 inches. Boards come in 12, 16, and 20 foot lengths, which lets a builder lay out a deck with as few end joints as possible.
That choice of length is not just about looks. Matching the board length to your deck dimensions reduces the number of seams where two boards meet end to end, which gives a cleaner surface and fewer spots to manage gaps. On a 20 foot deck, a single run of 20 foot boards can cover the span with no end joints at all, which is part of why those long boards are popular for larger projects.
| Line | Width | Thickness | Lengths |
|---|---|---|---|
| Transcend | 5.5 in | 0.94 in | 12, 16, 20 ft |
| Enhance | 5.5 in | 0.94 in | 12, 16, 20 ft |
| Select | 5.5 in | 0.82 in | 12, 16, 20 ft |
Source: Trex product specifications, 2026. Fascia and riser boards come in wider profiles.
One rule matters more than any other here: never mix Select boards with Transcend or Enhance on the same deck surface. Because Select is thinner, mixing lines leaves a small height difference between boards that becomes a real trip hazard. Keep the whole surface on one line so it sits flush.
If you are buying for a small project, you may also see Trex deck kits, which bundle boards and hardware for a defined footprint. Kits can simplify ordering for a simple platform or landing, but most full decks are still built from boards, fasteners, and accessories chosen to fit the exact design, which gives a builder more control over the layout.
Grooved vs. Square Edge Boards
Trex boards come in two edge styles, and the one you choose decides how the deck gets fastened. It is worth understanding the difference before you order.
- Grooved edge. A channel is cut into the long sides of the board so hidden fastener clips can slot in. This is the choice for a clean, screw-free surface, and it is what most main decks use.
- Square edge. A plain, solid edge with no groove. These boards are face-screwed from the top, then the screw holes are covered with color-match plugs that match the board. Square edge is the common pick for borders, stairs, and the deck perimeter where a grooved profile will not work.
Trex Deck Board Spacing and Gaps
Composite expands and contracts a little with temperature, so the gaps between boards are not optional. They give the boards room to move and let water drain through. Here are the spacing rules Trex calls for.
The recommended side-to-side gap between Trex boards is about 3/16 of an inch. End-to-end, where two boards meet at a joist, the gap runs roughly 1/8 to 3/16 of an inch, a little wider in cold weather since the boards are contracted when you install them. Boards should sit between 1/4 and 1/2 inch away from any solid object such as a wall or a post, and near water that gap widens to about 3/8 of an inch for extra drainage and airflow.
The good news is that the hidden fastener system does most of this for you. The clips have a built-in spacer leg that sets a consistent gap automatically, so you do not have to measure every joint. For square-edge boards, a spacer tool keeps the gaps even.
Temperature at install time is the detail people miss. Composite is contracted on a cold day and expanded on a hot one, so a board installed tight against its neighbor in January can buckle when July heat expands it. A good crew accounts for the install-day temperature when setting the end gaps, which is one more reason the gaps are not something to eyeball.
Joist Spacing and Framing Requirements
The frame under the boards matters just as much as the boards themselves. Composite is heavier than wood and needs solid, correctly spaced support to stay flat.
- Standard spacing. For boards run straight across the joists, 16 inches on center is the standard. This is the most common residential layout.
- Diagonal layouts. If the boards run at an angle, the joists need to be closer, at 12 inches on center, because the boards span a longer distance across the frame.
- Stairs and high-traffic areas. Stairs and heavy-use zones often call for tighter spacing, sometimes 12 inches or closer, for extra support underfoot.
A hidden fastener goes at every joist, no exceptions, which is why joist spacing also decides how many clips or screws you need. Because composite is heavier and shows every imperfection, the frame must be level and solid. Any dip or hump in the framing will telegraph straight up through the finished deck.
It also helps to know that Trex boards are designed to span at least three supports rather than just resting on two. That continuous support is what keeps the surface stiff and even, prevents bounce, and lets the boards carry weight without sagging between joists. Skipping joists or stretching the spacing to save lumber undermines exactly the stiffness the boards are built to provide.
Trex Fasteners: Clips, Screws, and Plugs
Trex offers a matched system of hardware, and using the right pieces is not just about looks. The wrong fasteners can void the warranty, so it pays to know the options.
Trex Hideaway Hidden Fastener Clips
The Hideaway Universal Hidden Fastener is the clip system for grooved boards. Each clip slides into the groove and is held with a single stainless steel screw driven into the joist. You install one clip per joist between each pair of boards, which is half the fasteners of a face-screwed deck. The clips set the gap automatically, leave the surface completely screw-free, and put fewer holes in the joists, which means less chance of water getting in. A Trex installation tool can speed the whole process up by as much as half.
Color-Match Screws and Trex Deck Plugs
For square-edge boards, the boards are face-screwed with color-match Trex screws, two per joist, and then the screw heads are hidden with Trex deck plugs that match the board color. The plugs tap into pre-drilled holes and sit flush, so the finished surface looks clean even though it was screwed from the top. This method is common on borders, stairs, and anywhere a grooved board will not work.
How Much Does Trex Decking Weigh?
One spec that catches people off guard is weight. Composite is noticeably heavier than wood, because the boards are dense, solid material rather than lightweight lumber. That extra weight is part of why Trex feels so solid underfoot, but it also means the frame has to be built to carry it.
In practice this matters most on two fronts. First, the substructure needs to be sound and properly spaced, since a frame built for a light wood deck may not be ideal for heavier composite. Second, if you are replacing an old wood deck with Trex, a builder should check that the existing framing can handle the added load before reusing it. For a brand-new deck, a crew simply frames for composite from the start.
Cutting and Working with Trex Boards
Trex cuts much like wood, with a few differences worth knowing. A standard circular saw or miter saw fitted with a fine-tooth carbide blade gives the cleanest edge, and Trex even offers a saw blade made specifically for cutting composite material. Because the material is dense, you let the saw do the work rather than forcing it, which keeps the cut edge smooth.
Cut ends on grooved boards do not need to be sealed, and you can rout a fresh groove into a cut end if needed for a hidden fastener. The key is a sharp blade and steady, unhurried cuts. Rushing a cut in dense composite is the fastest way to get a rough edge that shows on a finished board.
Essential Trex Accessories
A finished Trex deck uses more than just decking. A few accessories turn a bare frame into a polished, complete deck.
- Fascia boards. Wide trim boards that wrap the outside of the frame to hide the framing and give the deck a clean, finished edge.
- Riser boards. Matching boards that cover the vertical face of each stair step for a cohesive look from top to bottom.
- Joist tape. A self-adhesive moisture barrier applied to the top of the joists. It seals around fasteners and helps protect the wood frame from rot.
- Post sleeves and caps. Composite covers and caps that wrap structural posts so they match the rest of the deck.
- Deck lighting. Low-voltage stair, post, and rail lights that install into the deck for evening use.
- Edge and border trim. Trim pieces that finish exposed board edges and frame the deck, giving the perimeter a clean, intentional outline.
Frequently Asked Questions
How wide are Trex deck boards?
Trex boards are 5.5 inches wide across all the main lines. The width stays the same from Enhance to Signature, so only the thickness changes between lines.
How thick is Trex decking?
Transcend and Enhance boards are 0.94 inches thick, and Select boards are 0.82 inches. Because of that difference, Select should never be mixed with the thicker lines on the same surface.
What is the gap between Trex deck boards?
The recommended side-to-side gap is about 3/16 of an inch, with a slightly smaller end-to-end gap. Hidden fastener clips set this spacing automatically, and gaps near walls run 1/4 to 1/2 inch.
What joist spacing does Trex need?
Sixteen inches on center is standard for straight board layouts. Diagonal layouts need 12 inches on center, and stairs or high-traffic areas often use tighter spacing for added support.
How much does Trex decking weigh?
Trex is heavier than wood because the boards are dense, solid composite. The exact weight depends on the line and board length, but the practical takeaway is that the frame must be built to carry the added load.
How do you cut Trex decking?
Use a circular or miter saw with a fine-tooth carbide blade, and let the saw do the work for a clean edge. Cut ends on grooved boards do not need sealing, and a fresh groove can be routed into a cut end if needed.
Do I have to use Trex fasteners?
Trex strongly recommends its own clips, screws, and plugs, and using non-recommended fasteners can void the warranty. For a grooved deck, that means Hideaway hidden clips; for square edge, color-match screws and plugs.
The Bottom Line
Trex boards are 5.5 inches wide and come in 12, 16, and 20 foot lengths, with Transcend and Enhance at 0.94 inches thick and Select a touch thinner. Leave the right gaps, frame at 16 inches on center for a standard layout, fasten at every joist with Trex hardware, and finish the edges with fascia and the right accessories. Follow those specs and the deck stays flat, tight, and warranty-protected for decades.
These details are exactly where a seasoned crew earns its keep, since the spacing, framing, and fastening are easy to get subtly wrong. The naperville deck installation experts build to Trex spec every time, and a licensed deck contractor near barrington il brings the same precision to the north and northwest suburbs. If you are sourcing parts yourself, our rundown of deck fasteners and supplies and deck building supplies points you to the right local stock.
Whether you build it yourself or hire it out, knowing the specs puts you in control of the project. A deck built to these numbers is one you will never have to think about again.