PVC vs composite decking: what actually differs

PVC decking and composite decking are both plastic boards, but one has wood in it and the other doesn't. That one difference explains most of the rest. PVC is lighter and barely takes up water, and it holds its colour a little better, but in one maker's figures plain PVC moves more on a hot day. Composite is stiffer, cheaper and closer to timber in the hand. Calling both "plastic decking" hides how differently they behave on the frame.

What each one is

Composite is wood flour mixed with polyethylene and extruded, sometimes with a protective cap on the outside. One Australian board is close to half wood⁸, and the full story is in what is composite decking.

PVC decking is made entirely of polyvinyl chloride and has no wood in it. In a 2009 trade report, the PVC boards of two big US makers were described as a foam core inside a rigid cap². One range sold here describes its core as a foamed mineral-polymer mix under a double-layer polymer cap¹, and another is capped on all four sides⁴. Read what is PVC decking for the detail.

PVC vs composite decking: weight

Pick up a board of each and you'll know. One solid composite board 5.4 m long weighs a little over 22 kg⁸. A product director at a company selling both told a trade magazine in 2009 that foamed PVC can be as much as 40 per cent lighter than wood composite². The install guide for one PVC range sold here says its boards are lighter than typical wood-plastic composite and easier to handle. That matters on a balcony or rooftop where the dead load has to be checked, and it matters on the day the pallet arrives.

Stiffness and joist spacing

The foam that makes PVC light also makes it bendier. The same product director put the rigidity of foamed PVC at around half that of a wood composite, with the rigid cap adding some stiffness back². So PVC isn't a licence to widen the joists. The residential spans in one current PVC install guide sit around 400 to 450 mm¹, against a 450 mm maximum for a home deck from one composite maker⁶. I'd check the guide for the exact board, and composite decking joist spacing explains how spacing works under plastic boards.

Expansion: plain PVC moves more

Both materials grow along their length as they warm. The install guide for one PVC range sold here gives its plain PVC boards a coefficient of up to 0.07 mm per metre for each degree, which it calls about 50 per cent more than two of the maker's polyethylene-based ranges¹. The same guide's table lists the maker's polyethylene ranges at 0.040 to 0.045 mm per metre per degree, and its glass-fibre-reinforced PVC at 0.035, below them¹. So in this maker's figures plain PVC moves the most and the reinforced PVC the least. For comparison, a composite maker puts its own boards' growth at about 1.1 mm per metre between 15°C and a hot day⁷.

The guide's worked example is the one to remember. A five-metre plain PVC board installed at 22°C that later reaches 58°C needs about 12.6 mm of total end gap¹. The guide also says boards in direct sun can often be 25 to 30°C hotter than the air, so on those numbers a 30°C day in full sun puts a board in the high 50s¹. The practical rules follow from that. Use breaker boards between boards laid end to end, and a border around the edge. If the gap comes out bigger than you'd like, the guide's answer is to cut the boards shorter. In full sun, choose a lighter colour, because the guide says it reduces the expansion gap you need.

Composite isn't immune either. A Whirlpool member wrote in July 2020 that they had just replaced a five-year-old composite deck with merbau because it buckled and cracked in summer, and that they believed the previous owner had used cheap hollow boards¹².

Water, stains and swelling

Here PVC is the clear winner. With no wood in the board there's nothing organic for mould to grow on, and the makers market PVC as stain and mould resistant. One PVC range sold here is marketed for installs that may sit under water, and the maker says its boards won't swell even when submerged after cutting⁴. Composite takes up little water too, and one maker calls its capped board virtually waterproof apart from the cut edges⁶. There is at least one owner report of trouble. A reviewer in far north Queensland wrote on Ekodeck's ProductReview listing in February 2026 that the boards swelled and split in the wet season. Ekodeck replied that the photo appeared to show another brand's composite board¹⁴. In one Whirlpool thread, though, the worry was bigger than the reports. A member who started it in November 2023 was weighing a board described as "almost PVC" because they'd been told composite swells, and the owners who replied said they hadn't noticed swelling¹¹.

Stains follow the same logic, and a capped composite sheds most spills. Even so, one composite maker concedes that the best PVC has a slight edge over capped composite on fade and mould⁵, and an encyclopedia summary puts PVC ahead of other decking on fade, stain and mould resistance.

Heat

Both get hot, and I'd say colour decides more of it than chemistry does. One PVC maker says its boards are cooler to the touch than many other deck boards, then adds in a footnote that all decking gets hot in the sun and darker colours feel hotter³. An Australian composite maker allows that PVC dissipates heat slightly better than capped composite⁵. My advice is to treat the PVC heat advantage as real but small, and not to pick a dark PVC board for a pool surround on the strength of it. See does composite decking get hot, which has a section on PVC.

Scratches and feel underfoot

Cutting a PVC board exposes its foamed core, and the install guide says to plan the layout so those edges stay out of sight¹. Composite marks too. One Ekodeck owner on ProductReview wrote in February 2026 that a dropped tool gouged the thin plastic coating on the boards¹⁴. Underfoot, another owner on the same listing wrote in June 2026 that the deck feels solid¹⁴. An encyclopedia summary says PVC lacks the realistic feel of wood¹⁰. I'd stand on a sample of each before deciding, because feel is hard to judge from a brochure.

Fire, pools and balconies: where PVC is the better buy

One US maker said in 2009 that its PVC boards are self-extinguishing and won't keep burning on their own, and that two of its products were certified for California's wildfire zones². At least one PVC range sold in Australia is rated BAL 29⁴. A Whirlpool member building a pool deck in a bushfire area of far north Queensland in May 2023 was shopping for a BAL 29 composite. One brand they named offered it and another didn't, while a third seemed to offer only a higher rating¹³. Composite boards with a bushfire rating exist, and one maker says its capped board passed BAL 29 testing⁶. I'd still ask what frame the board was tested on. One composite maker's rating was achieved on aluminium joists⁹, so check with your certifier that it covers the frame you plan to build. The fire rating and BAL guide covers which brands publish a rating and what to have ready for a certifier.

Pools suit PVC because of the water and the salt, and one range sold here is tested in fresh, salt and chlorinated water⁴. Balconies and rooftops suit it because of the weight. On a plain backyard deck on a timber frame, I wouldn't pay for it. Composite decking around pools covers the composite side of a pool deck.

Cost tier

PVC sits in a higher tier than most composite. One composite maker's comparison has the two starting at similar prices, with PVC running up to about 20 per cent dearer⁵, and an encyclopedia summary calls PVC the most expensive synthetic decking. I won't put figures here because they change by state and by month. The prices page tracks live board prices, and the cost per m² calculator lets you compare the two on your own deck size.

Before you order

Ask for the install guide for the exact board, not the brand, and read the expansion table. If you're choosing PVC, ask whether the board is plain or reinforced, because that changes the gap. If the gaps it asks for would look wrong on your deck, choose a lighter colour or a shorter run. Then check the frame: PVC needs the same close joist centres as composite, and I'd have a balcony's weight checked either way. If your deck is a plain backyard job in part shade, composite will probably do the same work for less. If it's wrapping a pool, sitting on an apartment balcony or facing a bush block, PVC is where I'd start.