How to Install Trex Composite Decking: A Step-by-Step Guide

From the team at Griff Building Supplies — serving the Lower Mainland since 1964

Composite decking has become one of the most popular choices for homeowners and contractors across British Columbia. Trex, North America's leading composite decking brand, offers the look of real wood without the ongoing maintenance headaches. Whether you're building a new deck or replacing old pressure-treated boards, this guide walks you through the installation process from start to finish.

Why Choose Trex Composite Decking?

Before we get into the how-to, it's worth understanding why so many of our customers choose Trex:

• Low maintenance — no staining, sealing, or painting required
• Durable — resistant to rot, mould, insects, and fading
• Splinter-free — safer for bare feet and kids
• Eco-friendly — made from 95% recycled materials
• Warranty — backed by a 25-year limited residential warranty

What You'll Need

Materials:

• Trex composite decking boards (measure your deck area and add 10% for waste)
• Trex-compatible hidden fasteners (e.g., Trex Hideaway® Universal Fasteners)
• Stainless steel or coated screws (if face-screwing)
• Pressure-treated lumber for the subframe (joists, beams, posts)
• Joist tape or flashing tape
• Concrete footings or helical piles (if building from scratch)

Tools:

• Circular saw or miter saw with a fine-tooth blade
• Drill/driver
• Chalk line
• Speed square
• Tape measure
• Safety glasses and hearing protection

Pro Tip from Griff's: Stop by our New Westminster location or order online — we carry pressure-treated framing lumber, concrete, rebar, and hardware to get your subframe built right before the decking goes down.

Step 1: Build or Inspect Your Subframe

Trex composite decking requires a solid, properly spaced subframe. This is the most critical part of any deck build.

• Joist spacing: For standard 90° installations, joists should be spaced 16" on centre. For 45° diagonal installations, reduce spacing to 12" on centre.
• Use pressure-treated lumber rated for ground contact where applicable (especially posts and beams).
• Apply joist tape to the top of every joist. This protects the wood from moisture and extends the life of your subframe significantly.
• Ensure the frame is level and square before proceeding.

Step 2: Plan Your Layout

Before cutting a single board, plan your layout carefully:

• Snap a chalk line along the house or starting edge to ensure your first row is perfectly straight.
• Determine the direction of your boards — running them away from the house (lengthwise) is the most common approach and makes the deck appear larger.
• Account for a ¼" gap between the decking and any walls or fascia for drainage and expansion.

Step 3: Install the Starter Board

The first board sets the tone for the entire deck, so take your time here.

1. Position the first board along your chalk line, leaving the required gap from the house.
2. Face-screw or use hidden fasteners on the house-side edge (this edge will be hidden against the wall or fascia).
3. Use Trex Hideaway® fasteners on the field side — these clip into the grooved edge of the board and hold the next board in place while maintaining the proper gap.

Step 4: Install Field Boards

With your starter board in place, the rest goes quickly:

1. Slide the next board's grooved edge onto the fasteners from the previous row.
2. Press firmly and fasten the opposite edge with the next set of hidden fasteners.
3. Continue across the deck, checking alignment every few rows with your chalk line.
4. Stagger end joints by at least two joist bays for a cleaner look and better structural integrity.
5. Leave a ⅛" gap at all butt joints to allow for expansion and drainage.

Note on expansion: Composite decking expands and contracts with temperature. In BC's climate, always follow Trex's spacing guidelines — especially for installations done in cooler months.

Step 5: Cut and Fit the Final Board

The last board often needs to be ripped (cut lengthwise) to fit. Use a circular saw with a fine-tooth blade for a clean cut. If the cut edge will be visible, finish it with a Trex fascia board or trim piece for a polished look.

Step 6: Install Fascia and Trim

Fascia boards give your deck a finished, professional appearance by hiding the subframe and cut ends of the decking:

• Use Trex fascia boards in a matching or complementary colour.
• Face-screw fascia boards with colour-matched plugs or screws for a clean finish.
• Miter corners at 45° for a seamless look.

Step 7: Final Inspection

Before calling the job done, walk the deck and check:

• ✅ All boards are properly fastened with no movement
• ✅ Gaps are consistent throughout
• ✅ No high or low spots (use a straightedge to check)
• ✅ All cut ends are covered or sealed
• ✅ Fasteners are flush and not protruding

Maintenance Tips

One of the biggest selling points of Trex is how little upkeep it requires:

• Clean twice a year with soap and water or a composite deck cleaner
• Remove debris from between boards to prevent moisture buildup
• Avoid metal shovels in winter — use a plastic shovel or broom to clear snow

Ready to Get Started?

Griff Building Supplies has been helping Lower Mainland contractors and homeowners build better since 1964. We carry the framing lumber, concrete, hardware, and fasteners you need to get your deck subframe built right — and we can help you source Trex composite decking for your project.

Visit us at our New Westminster location, browse our products online, or give us a call — our team is happy to help you estimate materials and answer any questions.

Building better, together.