Choosing the right decking material is one of the most important decisions you'll make for your outdoor living space. Get it right and you'll have a deck that looks great and lasts for decades; get it wrong and you could be facing costly repairs or a full replacement within a few years. Whether you're building from scratch or replacing an ageing deck, the choice between timber and composite decking comes up for almost every NZ homeowner — and it's not always straightforward.
What Is Timber Decking?
Timber decking has been the go-to choice for New Zealand homes for generations. The most common species used locally include treated pine (H3.2 or H4 treated to meet NZ Building Code requirements for ground contact and weather exposure), kwila (also called merbau, an imported hardwood), and vitex. Locally sourced macrocarpa and cedar are also popular for their natural beauty and moderate durability.
Treated pine is by far the most affordable and widely available option — you'll find it at Mitre 10, Bunnings, and PlaceMakers. Hardwoods like kwila cost more upfront but are naturally denser and more resistant to rot and insects.
All structural decking framing in NZ must comply with NZS 3604 (Timber-framed buildings) and the NZ Building Code. If your deck is over 1.5 m above ground or attached to the house, a building consent is likely required — check with your local council or visit MBIE Building Performance for guidance.
What Is Composite Decking?
Composite decking is manufactured from a blend of recycled timber fibre and plastic (usually polyethylene or PVC), formed into boards that mimic the look of timber. It's been widely used in Australia and the US for years and has grown significantly in popularity across New Zealand over the past decade.
Composite boards come in two main types: solid core (heavier, very durable) and hollow core (lighter, more affordable). Most reputable brands offer a 25-year warranty. The surface is typically grooved or embossed to replicate timber grain, and colours range from natural wood tones to contemporary greys.
Composite decking is not a structural product — you still need a treated timber or steel subframe underneath, built to NZS 3604 standards.
Head-to-Head Comparison
| Criteria | Treated Pine | Hardwood Timber (e.g. Kwila) | Composite Decking |
|---|---|---|---|
| Upfront cost (boards only, guide only) | Lower | Moderate–High | Moderate–High |
| Lifespan | 15–25 yrs (with maintenance) | 25–40 yrs | 25–30 yrs |
| Maintenance required | High – annual oiling/staining | Moderate – oiling every 1–2 yrs | Low – occasional wash |
| Appearance | Natural, warm timber look | Rich, premium timber look | Consistent, timber-like look |
| Splinters/rough surface | Yes, especially as it ages | Less so | No |
| Slip resistance (wet) | Can be slippery when wet | Can be slippery when wet | Varies by product; check rating |
| Suitability for NZ coastal/humid areas | Moderate (needs correct treatment) | Good | Very good |
| Eco credentials | Sustainable if locally sourced | Mixed (often imported) | Good if recycled content |
| DIY friendliness | Good – standard tools | Moderate – harder to cut/fix | Good – clip systems available |
| Feels underfoot | Warm, natural | Warm, natural | Can feel warm/hot in direct sun |
Cost Considerations
It's tempting to compare only the upfront board price, but total cost of ownership tells a more honest story.
Treated pine boards are the cheapest to buy initially, but factor in the cost of annual cleaning, oiling or staining, and the likelihood of replacing boards that split, cup or rot within 15–20 years. Hardwood timber sits in the middle — pricier upfront, but less frequent maintenance.
Composite decking typically costs more per lineal metre for the boards themselves, but the ongoing maintenance cost is very low — usually just a wash down with a hose or mild detergent a couple of times a year. Over a 20–25 year period, the total spend can be comparable to or less than a well-maintained hardwood deck.
Always get at least two or three quotes from qualified deck builders. A good local tradesperson will help you factor in subframe costs, fixings, and finishing details. You can find experienced deck builders in your area on tradedirectory.co.nz.
For research on building material performance in NZ conditions, BRANZ is an excellent independent resource.
Maintenance: The Real Difference
This is where composite decking earns its premium. Timber requires consistent upkeep — if you skip a season of oiling, pine can grey, crack and splinter; kwila can leach tannins that stain surrounding surfaces. In high-humidity or coastal NZ environments (think Northland, the Coromandel, or Wellington's wet southerlies), untreated or poorly maintained timber deteriorates faster.
Composite decking largely sidesteps these issues. It won't rot, splinter, or need oiling. However, it's not completely maintenance-free — mould and algae can grow on the surface in shaded, damp spots, so a periodic scrub is still needed. Some cheaper composite products have also been known to fade or stain over time, so choose a reputable brand with a solid warranty.
Look and Feel
For many homeowners, nothing beats the look and feel of real timber — the grain variation, the warmth underfoot, the way it weathers naturally. A well-oiled kwila or macrocarpa deck is genuinely beautiful.
Composite has improved enormously in appearance over the past decade. Modern boards are convincing, and the colour consistency can actually be an advantage if you want a uniform, contemporary look. The downside: composite can get noticeably hot underfoot in direct summer sun — worth considering if you have young children or pets.
NZ-Specific Considerations
- Coastal areas: Salt air and moisture accelerate timber decay. Composite or well-treated hardwood is a better long-term choice near the coast.
- High UV areas: NZ's UV index is among the highest in the world. Both timber and composite can fade — look for UV-stabilised composite products and use quality UV-resistant oils on timber. Resene offers a range of deck oils and stains suited to NZ conditions.
- Slip resistance: This matters everywhere, but especially in wet regions. Check the slip resistance rating of any composite product (look for a P4 or P5 rating for wet areas) and use a non-slip additive in timber coatings.
- Licensed Building Practitioners: Structural decking work attached to a house is restricted building work under the NZ Building Act. It must be carried out or supervised by a Licensed Building Practitioner (LBP). Always check your builder's LBP licence before work begins.
Our Recommendation
Choose treated pine if: you're on a tight budget, comfortable with regular maintenance, and building a simple, functional deck in a sheltered location.
Choose hardwood timber if: you love the premium natural look, are prepared to maintain it properly, and want a deck that can last 30+ years with care.
Choose composite if: you want minimal ongoing maintenance, you're in a coastal or high-humidity area, you have young children (no splinters), or you want a consistent, modern aesthetic and are happy to invest more upfront.
For most NZ homeowners building a new deck today, composite decking offers the best balance of longevity, low maintenance and value over time — but only if you pair it with a properly built, code-compliant timber subframe. Don't cut corners on the structure.
Whatever you choose, get the job done properly. A qualified deck builder will ensure your deck meets the NZ Building Code, is consented where required, and is built to last. Find a trusted local professional at tradedirectory.co.nz.
Licensed Building Practitioner (LBP)
