What You Need to Install Trex Decking: Complete Materials List

To install Trex decking, you need Trex composite deck boards, a code-compliant substructure (typically pressure-treated joists and posts), hidden fasteners or screws designed for composites, and standard carpentry tools like a circular saw, drill, and tape measure. Most homeowners hire a professional for the job since the material cost alone runs roughly $6–12 per square foot for boards, and the structural framing underneath has its own requirements that must meet local building codes.

Does Trex Decking Need a Special Substructure?

Trex boards are the surface you walk on, but they don't support themselves. Underneath every Trex deck is a structural frame — called the substructure — made from lumber that carries the load. Trex composite boards are not structural, meaning they cannot span long distances without support the way a traditional wood joist can.

Here's what the substructure typically includes:

• Posts (4×4 or 6×6 pressure-treated lumber): Vertical supports anchored to concrete footings that hold the deck above ground.
• Beams (doubled 2×8, 2×10, or 2×12 pressure-treated lumber): Horizontal members that sit on top of the posts and carry the joists.
• Joists (2×6, 2×8, or 2×10 pressure-treated lumber): The parallel framing members that run across the beams. Trex requires joist spacing of 16 inches on-center for standard residential applications, or 12 inches on-center for diagonal board layouts or stairs. Always check Trex's installation guide for the specific product line you're using.
• Ledger board: A pressure-treated board bolted to the house to support one side of the deck. It must be flashed properly to prevent water intrusion.
• Rim joists / end joists: The perimeter framing that caps the joist ends.

Even though the decking surface is composite, the substructure is almost always pressure-treated wood. Some builders use steel framing for extra longevity, but that adds significant cost — often $3–6 more per square foot for the framing alone.

Which Trex Decking Boards Do You Need?

Trex sells several product lines at different price points. As of 2024, the main residential lines are:

These prices are for the boards only — not installation labor or substructure materials. Trex decking boards come in standard lengths of 12, 16, and 20 feet, and widths of about 5.5 inches (nominal 6-inch). You'll also need to decide between grooved-edge boards (which accept hidden fasteners) and square-edge boards (which are face-screwed). Most homeowners choose grooved-edge for a cleaner look.

How to Estimate How Many Boards You Need

Multiply your deck's length by its width to get the total square footage. Then add roughly 10–15% for waste — cuts, angles, and board-end offcuts add up. A 300-square-foot deck, for example, would need about 330–345 square feet of decking material. Your builder or lumber yard can do a precise takeoff from your deck plan.

What Fasteners Does Trex Decking Require?

You can't use standard wood-deck screws on Trex. Composite material expands and contracts differently than wood, and the wrong fastener can cause "mushrooming" (where the material pushes up around the screw head) or cracking.

Trex offers its own fastening systems:

• Trex Hideaway Hidden Fastener System: Small steel clips that snap into the grooved edges of the boards and screw into the joist. This leaves no visible screw heads on the deck surface. You'll need roughly one clip per joist per board, which works out to about 350–400 clips for a 300-square-foot deck at 16-inch joist spacing.
• Trex Start Clips: Specialty clips used for the first and last boards against the house and at the rim joist.
• Trex Universal Fasteners (TOPLoc or Cortex): Color-matched face screws used for square-edge boards or perimeter boards where hidden fasteners don't work. Cortex screws come with small composite plugs that fill the screw hole and nearly disappear.

Third-party hidden fastener systems like Camo Edge or Tiger Claw also work with Trex grooved boards, and some builders prefer them. Fastener costs typically add $0.50–$1.50 per square foot to your materials bill.

What About Railing, Stairs, and Trim?

Deck boards alone don't make a finished deck. Most projects also need:

Railing

Any deck more than 30 inches above grade requires a railing in virtually all U.S. jurisdictions — typically 36 inches high for residential (42 inches in some areas). Trex offers its own composite and aluminum railing systems:

• Trex Select Railing: Basic composite rail — around $30–$50 per linear foot installed.
• Trex Transcend Railing: Premium composite with a broader top rail — around $40–$70 per linear foot installed.
• Trex Signature Aluminum Railing: Sleek, modern look — around $50–$80 per linear foot installed.

You can also use third-party cable railing or aluminum systems, which many homeowners prefer for an unobstructed view.

Stair Components

Stairs require stair stringers (the notched diagonal supports, typically cut from 2×12 pressure-treated lumber), stair treads (Trex makes specific stair tread boards), and stair railing with special angled brackets. Most building codes also require a graspable handrail on at least one side.

Fascia and Trim

Trex offers fascia boards — thin composite panels that wrap the exposed pressure-treated rim joists and beams so everything looks finished. Without fascia, you'll see raw framing lumber from the sides and underneath. Fascia boards typically cost $3–$5 per linear foot for the material.

What Tools Are Needed to Install Trex Decking?

If you're hiring a builder, they'll bring their own tools. But for reference, here's the standard toolkit for a Trex deck installation:

• Circular saw or miter saw with a fine-toothed carbide blade (composites cut cleanly with standard carbide blades — no special blade needed, though a 60-tooth or higher blade gives smoother cuts)
• Cordless drill/driver for driving fastener clips and screws
• Chalk line and tape measure
• Jig for hidden fasteners (Trex's system includes a specific installation tool)
• Spacers — Trex recommends specific gap widths between boards (typically 3/16 inch for side gaps and 1/8 inch for end-to-end joints) to allow for thermal expansion
• Level, speed square, and string line for framing
• Post-hole digger or auger if new footings are needed

One thing to note: Trex boards generate fine plastic dust when cut, not sawdust. It's not hazardous like pressure-treated wood dust, but a dust mask and eye protection are still recommended.

Do You Need a Permit to Build a Trex Deck?

Almost certainly, yes. In most U.S. municipalities, any attached deck or any deck over a certain height (often 30 inches above grade) requires a building permit. The permit ensures your substructure, footings, ledger connection, and railings meet local building codes and load requirements. This is true regardless of whether the surface material is composite or wood.

Permit fees vary widely by location — typically $100–$500 for a standard residential deck, though some areas charge more. A reputable deck builder will pull the permit for you as part of their scope of work. If a contractor suggests skipping the permit, that's a red flag.

How Much Does a Full Trex Deck Cost Installed?

Putting all the materials and labor together, most homeowners pay roughly $30–$60 per square foot fully installed for a Trex deck, depending on the product line, complexity, railing, and local labor rates. A straightforward 300-square-foot deck with standard railing might run $12,000–$20,000 total. A multi-level deck with premium boards, aluminum railing, and built-in lighting could exceed $25,000–$35,000.

Here's a rough breakdown of where that money goes:

According to Trex's own cost estimator tool, the brand positions itself as a mid-to-premium decking option that costs more upfront than pressure-treated wood but less over time because it requires no staining, sealing, or replacing rotted boards.

What Other Materials Are Easy to Overlook?

Homeowners (and even some less experienced builders) sometimes forget these items when planning a Trex deck project:

• Joist tape: Self-adhesive butyl tape applied to the tops of joists before decking goes down. It prevents moisture from sitting on the joist and accelerating rot. A roll costs around $20–$50 and is cheap insurance for the substructure's longevity. Trex recommends it.
• Ledger flashing: Metal flashing that goes behind the ledger board where the deck attaches to the house. Without it, water gets behind the ledger and can rot the house's rim joist or band board — one of the most common causes of deck failure.
• Concrete and post bases: Footings need concrete (either poured or pre-cast piers) and often adjustable post bases to keep wood posts from sitting directly in the ground.
• Post sleeves: Composite wraps that cover the structural 4×4 or 6×6 posts so they match the deck's finished look. Trex offers these for about $40–$80 per post.
• Under-deck drainage (optional): Systems like Trex RainEscape create a dry space under an upper-level deck by catching water between the joists. This adds roughly $3–$5 per square foot.

A Quick Pre-Project Checklist

Before you or your builder starts ordering materials, make sure you have:

1. A deck design or plan with dimensions, including stair locations and railing runs
2. A building permit (or confirmation that your builder will obtain one)
3. A confirmed Trex product line and color selection
4. Joist spacing verified against Trex's installation guide for your specific board profile
5. A materials takeoff (itemized list of every board, fastener, and hardware piece with quantities)
6. A clear understanding of your lot — soil conditions, slope, and distance from property lines can all affect the build

Getting multiple quotes from experienced composite-deck builders is the single best way to avoid cost surprises. Experienced installers know the Trex system's quirks — like expansion gaps, starter-board placement, and proper ventilation under low-clearance decks — and can save you from expensive mistakes.

Ready to start planning? Get matched with a local deck builder using the form on our home page. You'll receive quotes from pre-screened contractors in your area who have experience with Trex and other composite decking systems.