Is merbau decking any good?

Yes — it's the value hardwood for a reason. Merbau is dense, naturally durable (Class 1–2 above ground), extremely stable in Sydney humidity, and one of the seven species deemed suitable for BAL-29 bushfire zones. Its two catches are honest ones: it bleeds tannins for the first months (we pre-wash boards and keep them clear of light paving), and most merbau is imported from South-East Asia, where sourcing standards vary — ask for certified, legally sourced stock or consider an Australian-grown hardwood instead.

Spotted gum or blackbutt for decking?

You can't pick badly — both are Australian hardwoods rated Class 1 for above-ground durability and both meet BAL-29 bushfire requirements. Spotted gum is the darker, richer board with wavy grain and slightly higher density; it sits at the premium end of the timber market. Blackbutt is paler and cleaner-lined, takes oil very evenly, and suits contemporary houses. It usually comes down to the look you want against your house — we bring samples of both to the site visit.

Does composite decking get hot?

Dark composite boards get noticeably hot in full summer sun — hotter than light-coloured timber. On a west-facing deck or a pool surround we steer people to lighter colours, and we say so before boards are ordered. Details on the brands we install are on the composite decking page .

How long does a hardwood deck last?

Hardwood boards on a properly built substructure are a 25–40 year proposition with basic care — an oil every 12–18 months in open sun, longer between coats in shade. The substructure decides it more than the boards do, which is why ours is H4-treated or steel on engineered footings, with fixings graded for coastal air.

Which decking is best for bushfire zones?

For decks that must meet BAL-29 under AS 3959, only seven naturally fire-resistant timbers can be used without extra treatment — and spotted gum, blackbutt and merbau are all on that list. Treated pine is not. Some composite boards carry their own BAL ratings, but it varies by product, so the specific board's certification has to be checked. Above BAL-29 the rules tighten again, and the answer becomes site-specific.

Is merbau decking sustainable?

This is merbau's weak point and it deserves a straight answer: much of the world's merbau is cut from natural forest in South-East Asia, and illegal logging has been a documented problem in the trade. Certified, legally sourced merbau exists and is worth insisting on. If provenance matters to you, spotted gum and blackbutt are Australian-grown, largely from regrowth and managed forests, and give up nothing on durability.

Deck Materials Compared: Timber vs Composite

The short answer

For most Sydney decks the choice comes down to five materials. Spotted gum andblackbutt are the premium Australian hardwoods — both rated Class 1 for above-ground durability, both suitable for BAL-29 bushfire zones, both wanting an oil every 12–18 months. Merbau is the value hardwood: nearly as durable, very stable, with sourcing questions worth asking. Treated pine is the budget board for painted decks. Composite — Trex, Millboard, ModWood — costs more up front and then asks almost nothing of you: no oiling, no splinters, no grey-out. The right one for your deck depends less on the showroom and more on your site's sun, shade and salt.

Material	Durability	Maintenance	Bushfire (BAL-29)	Look & ageing	Worth knowing
Merbau	Class 1–2 above ground	oil every 12–18 months	yes — one of the seven deemed species	deep red-brown; silvers if left uncoated	tannin bleed early on; sourcing varies — insist on certified stock
Spotted gum	Class 1 above ground	oil every 12–18 months	yes — deemed species	rich brown, wavy grain; silvers evenly	Australian grown; premium end of the timber market
Blackbutt	Class 1 above ground	oil every 12–18 months	yes — deemed species	pale blonde, clean-lined; silvers evenly	Australian grown, largely regrowth; takes oil very evenly
Treated pine	durability from H3 treatment, not the timber	paint or stain every few years	no — not a deemed species	plain; needs coating to look finished	the honest budget answer for painted decks
Composite (Trex, Millboard, ModWood)	no timber class; capped boards carry long manufacturer warranties	wash with soapy water — that's it	varies by product — check the specific board's rating	holds its colour; never silvers, can't be sanded	dark colours run hot in full sun; damaged boards are replaced, not repaired

Durability classes are the Australian standard's ranking of a timber's natural resistance to decay — Class 1 is the top tier, and it's why spotted gum and blackbutt decks shrug off decades of weather that would finish a softwood. Composite sits outside that system entirely: its boards don't rot, so the question shifts from durability to fade, heat and warranty.

We build in every material on this page and carry samples of all of them.See our deck building service or send a photo of the space below — we'll tell you what we'd put there and why.

How to choose by site, not by showroom

The same board behaves differently on different blocks, and the Lower North Shore serves up most of the hard cases.

Full sun, west-facing: sun is what ages decks. Hardwood here means a disciplined oiling rhythm or a graceful silver; dark composite gets hot enough underfoot to notice in January. Light composite colours or a blonde hardwood like blackbutt are the comfortable answers.
Deep shade and overhanging trees: the opposite problem — timber stays damp, grows moss and wants more attention, not less. This is where capped composite earns its keep, because a wash-down is the whole maintenance program.
Coastal air: near the harbour the boards matter less than the fixings — cheap screws rust and streak whatever they hold down. Dense, stable species (merbau is excellent here) plus stainless or hot-dip galvanised fixings is the combination that lasts.
Pool surrounds: composite's best use case. No splinters for bare feet, no oil to wash into the water, and capped boards shrug off splash and chlorine. If it's in afternoon sun, choose a light colour.

Timber vs composite, honestly

Both camps oversell. The truthful version: timber is cooler underfoot, ages into something composite can't imitate, and is repairable board by board — a scratched or stained hardwood board sands back to new. Its price is the maintenance rhythm, and skipping it means grey, dry boards (recoverable, but cheaper to keep up than to catch up). Composite trades that rhythm away: it keeps its colour, never splinters and cleans with soapy water — but a damaged board can't be sanded, only swapped, and matching a replacement to a batch that's a few years old is harder than the brochures admit. Dark composite in full sun runs hot; timber doesn't. Neither is the better product — they're different bargains, and which one suits you is mostly a question about how you'll actually live with the deck.

Maintenance, year by year

Material	Year one	Ongoing	If you neglect it
Spotted gum / blackbutt	handed over freshly oiled; first re-coat at about 12 months	oil every 12–18 months in sun, longer in shade	boards silver and dry out — a sand and re-oil brings them back
Merbau	pre-washed for tannin bleed, then oiled; re-coat at about 12 months	same oiling rhythm as the other hardwoods	silvers like the others; tannin staining on paving is the early-days risk
Treated pine	coated once boards have dried out	re-paint or re-stain every few years	coating flakes, timber weathers — cosmetic first, structural eventually
Composite	nothing — wash before the first barbecue if you like	soapy-water wash a couple of times a year	very little happens — dirt and mould wash off capped boards

Bushfire zones change the shortlist

Parts of the Lower North Shore — the leafy edges of Castlecrag, Northbridge and around the bushland reserves — sit on mapped bushfire-prone land, and a deck attached to a house there must be built to the site's Bushfire Attack Level under AS 3959. At BAL-29, decking timber must be one of just seven naturally fire-resistant species — and it's no accident that spotted gum, blackbutt and merbau are all on that list. Treated pine isn't. Composite varies board by board: some products carry BAL ratings, many don't, so the specific board's certification gets checked before anything is ordered. If your block is mapped, the BAL rating is the first fact we establish, because it can quietly delete half the options from this page.

Not sure whether your block is bushfire-mapped, or what your BAL rating means for boards? We confirm it as part of every deck quote, in writing, before you choose a material.Start with the deck building service or ask below.

What we build with on the Lower North Shore, and why

Most of our timber decks go down in spotted gum or blackbutt: Class 1 durability, BAL-29 compliance for the leafy blocks, and they simply belong against sandstone and federation brick. Merbau is the value pick we're happy to build with when the stock is certified and the client knows about the tannin wash. Treated pine we keep for painted decks and structures the eye won't linger on. On the composite side we install ModWood, Trex and Millboard only — boards whose ten-year-old decks we can point to — laid to the manufacturer's span and ventilation specs, which is what keeps the warranty valid. Whatever goes on top, the substructure underneath is the same: engineered footings, H4-treated or steel framing, and stainless or hot-dip galvanised fixings for coastal air. The boards get the compliments; the framing does the work. The full detail lives on ourtimber decking andcomposite decking pages. If the existing boards are tired rather than gone, start with deck repairs and restoration instead; and before any new build, check whether it needs sign-off in ourdeck council approval guide.

Deck Materials Compared: Merbau, Hardwoods & Composite