How to install composite decking: the steps that matter

Laying composite boards is the easy half of the job. The frame and the gaps are the hard half, and the boards look as good as what is under them and no better. The order I'd follow on any composite deck starts with the frame. Then the first board goes down off the open edge, and each board is fixed at each joist, with the joists doubled under any butt join and the end gaps set from the maker's table for the day's temperature. A breaker board, a border or a fascia closes the deck off. The makers publish an installation guide for their boards and tie the warranty to following it, so read the one for the boards you have bought before you open a pack.

How do you install composite decking? The order I'd follow

1. Check the frame before anything else. One guide asks for the frame to be completely level before any board goes on⁴, and I'd treat that as non-negotiable, because a board laid over a dip follows it. Run a string line across the joist tops and pack or plane any that are out. On timber joists, add joist tape, which two of the guides here recommend. If the frame is still to be built, my guide to building a deck frame for composite decking covers it from the posts up.
2. Confirm the joist centres against the guide. The common residential figure in Australian guides is 450 mm, and one manual drops to 400 mm for stairs, landings and commercial decks¹. One imported brand's Australian web page gives 400 mm as the maximum for its boards⁵. Boards laid on an angle need the joists closer again. The full detail is in my guide to joist spacing for composite decking.
3. Let the boards settle. One guide asks for the boards to sit flat on site for at least two days before you fix them, to cut down on shrinkage during and after the install⁴. Don't fix boards that have been baking in a stack. One maker says to fix its boards when they are out of full sun and the air is under 25 degrees².
4. Start from the open edge, not the house. One manual recommends starting at the step or outer edge and working back to the wall¹. A full-width board then sits on the edge people see, and the board that needs ripping to width ends up against the house.
5. Fix every board at every joist. Screw systems take two screws per joist crossing, pre-drilled and countersunk². In a clip system each clip sits on its own joist. I wouldn't skip joists to save fixings, because it leaves a length of board free to lift.
6. Double the joist under every butt join. Each board end must sit on its own framing, so where two ends meet you add a sister joist beside the original and fix each end to its own timber⁴. Stagger the joins so they never line up across the deck.
7. Leave the end gaps for the temperature on the day. Composite grows and shrinks along its length with heat, so the gap at a board end depends on how warm the board is when you fix it. In one manual's table, a full-length board fixed at 10 degrees gets 4 mm at each end, and one fixed at 40 degrees gets 1 mm¹. More in my guide to expansion gaps in composite decking.
8. Finish the edges. A breaker board or a picture-frame border hides the cut ends and needs blocking under it, and a fascia needs a rim joist to fix to. The framing for both is in picture-frame borders on a composite deck.

What the first board decides

The first board sets the line for the whole deck, so spend the time on it. One guide recommends fitting boards to a string line, and I'd do that rather than trust any wall or old fascia to be straight. The first board also needs its own fixing on its outside edge, because there is no neighbouring board for a clip to grip. Depending on the guide, that is a starter clip or a face screw, and one manual also allows an angle bracket under the board¹. If it is a screw, pre-drill and keep it the minimum distance from the end. One guide puts that at 15 mm from the end and 20 mm from the edge², and another at 38 mm from both⁴.

At the other end of the job, the last board meets the house. Leave the gap the guide gives between the boards and any wall or post. One maker asks for a minimum of 6 mm to a solid structure², and another for 10 mm to a wall or door⁶. The gap at the wall is the room the deck has to grow into on a hot afternoon. A board fixed hard against brickwork has nowhere to go but up.

Clips or screws

Most of the boards in the makers' guides cited here are grooved on the edges for a hidden clip. The clip sits in the groove, screws down into the joist and sets the gap to the next board as you go. I'd expect clips to be quicker than screws once you have a rhythm, and they leave a clean surface. Face screwing is allowed on some ranges and needed for the last board, but it comes with a rule about pre-drilling slightly oversized holes so the board can move⁴. The trade-offs are in hidden clips vs face screws.

One point is easy to miss: the clips and the gap rules are separate. One maker's fixing instructions say its standard side, butt-join and end gaps still apply when you use concealed clips². Clips set the side gap for you. The end gap is still yours to get right.

The mistakes owners and installers report

Owner and installer reviews on ProductReview, and build threads on Bunnings Workshop, point to three trouble spots.

The first is gaps that move before the boards are held. A ModWood owner in New Zealand wrote on ProductReview in March 2023 that on the evening the builders finished, some of the butt-join gaps were far wider than the instructions described⁹. The spacers were loose and the boards had slid along the clips before the adhesive set, and the owner had to push them back and wedge the ends. My advice is to walk every butt join and check the gaps against the spacers before you leave the deck for the night.

The second is the frame. A Bunnings Workshop member who built a small low-profile composite deck in July 2026 kept the joists between 350 mm and 400 mm apart, taped them and used the clip system the board maker sells¹¹. That is a sensible margin inside the residential figures above. An old timber frame needs checking before composite goes on it, because a frame built for timber boards may be at wider centres than composite allows. My guide to laying composite decking on an existing deck frame covers what to look for.

The third is clip consistency. An Ekodeck owner called Sue wrote on ProductReview in April 2025 that the "Clips are very good helping with the overall look and quality"⁷. An installer reviewing on the same site in June 2026 described two tubes of clips that measured a millimetre apart, which pushed the boards about 20 mm out of line over 40 boards⁸. The maker replied that it had not seen that variation before. Check a few clips from each packet against each other before you start, and measure the running total every few boards so a small error cannot become a wedge-shaped gap at the far end.

How hard is it to install composite decking?

I'd say anyone who can build a level timber frame can lay the boards. One manual recommends a 60–80 tooth blade for cutting them in a drop saw¹, and the clips are simple to fit. A couple who built their first deck themselves wrote on ProductReview in September 2024 that they could "trim and rip the product very easily"⁸. A NewTechWood owner who laid a first composite deck as a DIY job called it a fairly easy project, and later advised fitting the boards a little long and sawing them to length once they are down¹⁰. One manual recommends the same thing.

The harder part is the frame. Closer joist centres, doubled joists at every join, blocking under borders and ground clearance for ventilation all add timber and time compared with a hardwood deck. One guide asks for at least 40 mm of clearance over concrete and 100 mm over soil⁴. Another asks for 300 mm over the ground and 50 mm over concrete². If your site cannot give the clearance, you are into a low-profile frame or pedestals, and that is a different build. See building a ground-level composite deck and composite decking over concrete.

Call a builder when the deck is high enough to need a balustrade or a permit, or when the frame is old and you cannot see the post bases. Stairs and borders on more than one side are also a job for someone who has done them before, and my guide to composite decking stairs explains what they involve.

Before you order

• Download the installation guide for the exact range and read it end to end. One maker's fixing instructions say that not following them voids the warranty².
• Count joists at the guide's centres, then add one joist per butt join and blocking under every border and breaker board.
• Buy the clips or screws the guide names. One maker allows other concealed fixings only with its written permission and bans fixings that dig into the side of the board³.
• Plan to fix boards on a mild day and keep the packs in the shade until you need them.
• Use the joist calculator for a first count of framing timber, then take those concept figures to whoever is building the frame.