A builder specs a subframe for treated pine, then the client switches to composite at the last minute. The boards show up 30% heavier than expected. Now the joist spacing is wrong, the footings are borderline, and the job is behind before a single board goes down.
Most weight guides give you one generic number for each material. That’s not how it works. A hollow composite board and a solid one can differ by 45%. Freshly treated pine can weigh 50% more than kiln-dried stock. The gap changes the subframe spec, the freight cost, and how your crew handles boards on site.
This article gives you actual kg/m figures — composite and Australian timber side by side — so you can plan for all of it.
How Much Heavier Is Composite Decking Than Wood?
Solid composite decking is usually 20–30% heavier than dry treated pine of the same size. But hollow composite boards can weigh the same as pine — or even less. The real weight difference depends on four things: board profile (hollow or solid), board size, timber species, and moisture content.
A hollow composite board at 150×23 mm can weigh around 2.78 kg per metre. A kiln-dried treated pine board of similar size weighs roughly 1.8–2.0 kg per metre. That’s a gap — but not a dramatic one.
Switch to solid composite boards or compare against a dense hardwood like spotted gum, and the numbers flip. Spotted gum decking can weigh as much as — or more than — solid composite.
The point: “composite vs wood” isn’t one comparison, it’s several.
Why Is Composite Decking Heavier?
Composite decking blends wood fibres with plastic resin — usually HDPE. The mix is heated and pressed into boards, which removes the air pockets found in natural wood. The plastic resins fill gaps that natural wood leaves open, so the board ends up denser and heavier.
A typical capped composite board uses hardwood fibre combined with HDPE at around 0.95 g/cm³ density, with recycled content often making up 60% or more of the mix. Most quality products follow a similar production process. The composite wood is simply more packed with material per metre than pine.
Real Weights — Composite vs Timber per Metre
This is where the numbers matter. The table below compares composite deck boards against common Australian timber decking species, all in kilograms per linear metre.
Composite weights are from published LastElegance product specs. Timber weights are calculated from density data: treated pine (radiata) at 545 kg/m³ (Business Queensland), merbau at 800–850 kg/m³ (USDA Wood Handbook), and spotted gum at 950 kg/m³ (Business Queensland). All timber figures assume kiln-dried stock at 12% moisture content.
| Board | Dimensions (mm) | Weight (kg/m) |
|---|---|---|
| Renew (hollow) | 150 × 23 | 2.78 |
| Renew (hollow) | 140 × 23 | 2.90 |
| VerdeLife (solid) | 139 × 24 | 3.10 |
| TimberLuxe (solid) | 140 × 20 | 3.72 |
| TimberLuxe (solid) | 140 × 23 | 4.20 |
| Treated pine | 140 × 19 | ~1.45 |
| Treated pine | 140 × 22 | ~1.68 |
| Merbau | 140 × 19 | ~2.26 |
| Spotted gum | 140 × 19 | ~2.53 |
| Spotted gum | 140 × 22 | ~2.93 |
Timber weights are estimates based on published air-dry densities at 12% MC. Actual weights vary by grade, cut, and moisture. Always confirm from the latest product spec sheet.
The gap between a hollow composite board and treated pine is real. But compare it to merbau or spotted gum at the same width, and the weight difference shrinks fast.
How Board Profile Changes the Number
The composite weights in the table above aren’t one number — they shift with board profile. Look at two LastElegance boards at 140 mm width: Renew (hollow) at 2.90 kg/m vs TimberLuxe (solid) at 4.20 kg/m. That’s a 45% difference just from the profile change.
A hollow composite board can weigh less than dense hardwood like merbau or spotted gum. A solid composite board will weigh more. Board profile matters as much as the decking material itself. For a deeper look at the trade-offs, see our Hollow vs Solid Composite Decking guide.
Why Timber Weight Varies So Much
Timber weight changes with species, moisture content, and grade. The type of timber makes a big difference: treated pine (radiata) sits around 545 kg/m³ when kiln-dried, while spotted gum reaches 950 kg/m³. That’s nearly double the density for the same volume.
Moisture is the other wild card. Freshly treated pine can hold 50% or more extra water weight compared to kiln-dried stock. On a real job site, those “light” pine boards off the delivery truck can feel closer to hardwood until they dry out. Traditional wood decking doesn’t have a single weight — it has a range, and that range is wide. When you’re planning a subframe or costing freight, always ask: which species, and how dry?
Does the Weight Affect Your Subframe?
This is the question builders ask most. The short answer: composite decking is heavier per metre than treated pine, but the difference rarely needs a full subframe redesign.
Joist spacing for composite decking typically ranges from 300 to 450 mm, depending on the brand and board profile — solid boards and heavier traffic areas usually need the tighter end. Board flexural strength in a quality capped range sits around 26 MPa (tested to EN 15534). Follow your chosen manufacturer’s install guide and the relevant sections of the NCC, and the subframe should handle the load.
Three things to check before switching a timber deck to composite:
- Joist spacing — check the composite manufacturer’s install guide for the exact spec. Don’t assume your existing timber spacing is close enough.
- Bearer and footing capacity — add the weight difference per square metre and check the existing structure can take it, especially on elevated or multi-storey decks.
- Fixing method — composite uses hidden clips, not face screws. Make sure joist tops are flat and consistent.
If you’re building a new deck from scratch, the subframe design simply follows the composite spec from the start. The weight difference only matters when you’re retrofitting.
Need project-specific guidance? Contact our team for help speccing the right subframe.
Is Composite as Strong as Wood?
Composite and timber have different strength profiles. A quality capped composite board tests around 26 MPa in flexural strength (EN 15534) — strong enough for foot traffic and furniture loads at 300 mm joist spacing.
The honest trade-off: composite has less stiffness than hardwood and flexes more under point loads. But it holds that strength over time — no rot, no warping, no soft spots from water damage. Wood decking starts strong and gets weaker as it ages. Composite stays consistent. That’s why joist spacing matters more than raw board strength.
Handling, Carrying, and Install Speed
Weight on a spec sheet is one thing. Weight in your hands at 7 a.m. on a second-storey job is another.
A 2.9 m hollow composite board (like the Renew at 2.78 kg/m) weighs about 8 kg. One person carries that easily. A solid board at the same length (like TimberLuxe at 4.20 kg/m) comes in at roughly 12.2 kg — still a one-person lift, but worth planning for on a full day of installs on a second-storey deck.
For context, a 2.9 m spotted gum board at 140×19 mm weighs about 7.3 kg. Merbau at the same size comes in around 6.6 kg. The lighter composite boards sit right in the range of common hardwood decking.
Where composite wins back time is the install. Most capped composite systems use hidden clips — stainless steel fasteners that slot into the board grooves and clip onto the joist. No pre-drilling. No face screws. The next board slides in, and you move on. On a typical outdoor project, that speed gain can offset any extra handling weight. Builders in coastal Queensland tell us the clip system is what sells the switch for their crews.
Want to feel the weight and clip system yourself? Request free samples and try them on your next outdoor space project.
How Weight Affects Freight and Long-Term Cost
Heavier boards cost more to ship. On a full container of composite decking, the freight bill will be higher than the same volume of treated pine. Factor that into your quote.
But freight is a one-time cost. Maintenance is ongoing. Composite needs no annual oiling, no sanding, and no board replacements from rot or termite damage. When you’re comparing composite decking vs wood on total project cost, weigh the freight gap against years of zero upkeep. For most jobs, the low maintenance maths favours composite.
Request a quote from LastElegance with your quantities, and we’ll give you landed pricing.
Frequently Asked Questions
Are there building code concerns when switching from wood to composite decking because of weight?
The NCC and AS 1170.1 set load requirements for decks. The weight difference between composite and timber is usually small enough that a code-compliant subframe for timber will also suit composite. For elevated or high-load decks, confirm with the manufacturer’s install guide and check with a structural engineer.
How much does composite decking cost vs wood over time?
Composite has a higher upfront cost but needs far less upkeep — no oiling, staining, or sanding. Over 10–15 years, total cost of ownership often favours composite. Warranty periods reflect that: the Renew range covers 15 years, VerdeLife 20 years, and TimberLuxe 30 years.
How do heat and cold affect a composite deck vs wood?
Composite expands and contracts slightly with temperature changes. Any good install guide will account for this with recommended expansion gaps. Timber also moves, but mostly with moisture changes rather than heat. Neither issue is related to board weight.
Will replacing a wood deck with composite boards increase the total deck weight much?
On a typical 20 m² deck, the total increase might be 40–80 kg depending on board profile. That’s usually within the capacity of an existing code-compliant subframe. A builder should always check bearer and footing specs before starting — especially on older structures.
What is the typical weight per square metre for composite deck boards?
It varies by profile and dimensions. Quick example: the Renew 150×23 mm weighs 2.78 kg per linear metre. At 150 mm cover width, you need about 6.7 boards per metre of deck width — so roughly 18.6 kg/m². A solid TimberLuxe at 140×23 mm works out closer to 30 kg/m². Always check the product spec sheet for exact figures.
