Merbau vs Spotted Gum Decking: Which Should You Choose?

Merbau vs spotted gum decking comes down to two things: tannin risk and price. Spotted gum is the better decking timber if you want colour that stays consistent and don’t want to deal with tannin stains in the first year. Merbau is the better choice if price matters more and you’re prepared to oil the boards a few times in the first six months to control bleeding. Both are Class 1 durability hardwoods rated for 40-plus years above ground, so neither will let you down structurally. The real difference is upfront cost (spotted gum runs 75 to 80% more per metre) versus early-life maintenance (merbau needs tannin control that spotted gum mostly skips).

If you’re planning a new deck or resurfacing an old one before summer, here’s exactly how the two timbers compare, using current Lifetime Pine stock and pricing.

What’s the Difference Between Merbau and Spotted Gum Decking?

Merbau (Intsia bijuga) is a dense tropical hardwood, typically supplied kiln-dried, with a red-brown colour that deepens with age. It’s the most widely used decking timber in Victoria because it’s affordable, stable, and stocked in long lengths. Its main quirk is tannin: merbau is naturally tannin-rich, and rain on fresh, unsealed boards will wash reddish-brown tannin onto anything below, including pavers, render, and pool edges.

Spotted gum (Corymbia maculata) is a native Australian hardwood with a tighter grain and a colour range from pale grey through to chocolate brown and red-brown. It bleeds tannin far less than merbau and holds its colour more evenly board to board, which is why it’s the pick for decks near light-coloured paving, pools, or rendered walls.

Which Decking Is Cheaper, Merbau or Spotted Gum?

In the merbau vs spotted gum decking price comparison, merbau is cheaper at every board width Lifetime Pine stocks. At a standard 90mm-class width, merbau runs $5.60 a metre against $9.90 a metre for spotted gum, a 77% premium. At the wider 135 to 140mm boards, merbau is $10.00 a metre against $18.00 a metre for spotted gum, an 80% premium. On a typical 20m2 deck (roughly 130 linear metres of board at 140mm width), that’s the difference between about $1,300 in board cost and $2,340.

Spec	Merbau Decking	Spotted Gum Decking
Durability class (above ground)	Class 1 (40+ years)	Class 1 (40+ years)
Tannin bleed	Significant in first few rains, needs oiling	Minimal
Colour	Red-brown, deepens with age, more board-to-board variation	Pale grey to chocolate/red-brown, more consistent
Price, 90 x 19mm / 86 x 19mm	$5.60/metre	$9.90/metre
Price, 140 x 19mm / 135 x 19mm	$10.00/metre	$18.00/metre
Workability	Easier on blades and drill bits	Denser, harder on tools, pre-drilling recommended
Best suited to	Budget-conscious builds, decks away from light paving/pools	Decks near pools, pale pavers, render, or where colour consistency matters

Does Merbau Decking Bleed Tannins?

Yes, and it’s the single biggest complaint about merbau decking in Victoria. Unsealed merbau will leach reddish-brown tannin the first several times it gets properly wet, and that runoff stains anything porous underneath: concrete, light pavers, render, and pool coping are the usual casualties. The fix is straightforward but not optional: oil both sides and all edges of every board before or immediately after installation, and reapply within the first few weeks. A tannin remover (oxalic acid based) will lift stains that do land on paving, but it’s easier to prevent than to clean up after the fact.

Spotted gum isn’t tannin-free, but it bleeds far less and rarely causes the same staining problems, which is the main reason builders reach for it around pools and light-coloured hardscaping.

Which Board Width Should You Choose?

Lifetime Pine stocks both timbers at a narrow, standard width (merbau 90mm, spotted gum 86mm) and a wider board (merbau 140mm, spotted gum 135mm). The narrower boards suit smaller decks, curved edges, and diagonal lay patterns, since they flex more easily and show less gap variation over a run. The wider boards cover a deck faster (fewer boards, fewer joints per square metre) and read as a more contemporary, fewer-lines look, but they’re less forgiving on timber that isn’t fully seasoned, since wider boards cup and gap more visibly if they move.

For a straightforward rectangular deck laid parallel to the house, the wider board is usually the better buy: it’s fewer lineal metres of screwing and, on spotted gum in particular, fewer joins to keep tannin-free.

When’s the Best Time to Build a Deck in Melbourne?

Spring, right now, is the window builders and DIYers both prefer. Timber moves less in mild, drier weather than it does after a wet winter, ground conditions are easier to dig and level footings in, and a deck finished in September or October has a full season to cure and take its first coat of oil before you’re using it hard over summer. Leave it until December and you’re racing entertaining season with green timber and a queue at the timber yard.

Merbau vs Spotted Gum: Which Should You Choose?

When you’re weighing up merbau vs spotted gum decking, the decision mostly comes down to budget versus tannin risk. Choose merbau if budget is the deciding factor, the deck isn’t next to light pavers, render, or a pool, and you’re comfortable oiling the boards two or three times in the first year. Choose spotted gum if the deck sits near anything the tannin could stain, if you want the colour to stay predictable board to board, or if the extra $4 to $8 a metre is a rounding error against the rest of the build. Structurally, you can’t go wrong either way. Both are Class 1 durability hardwoods that will outlast most of what’s built around them.

Frequently Asked Questions

Is spotted gum better than merbau for decking?

Spotted gum is better if you want to avoid tannin staining and want more consistent colour. Merbau is better value and is the more common choice where budget matters more than early-life maintenance. Neither is more durable than the other for a standard above-ground deck.

How long does merbau tannin bleed last?

Most of the bleeding happens in the first few months while the boards weather and are exposed to rain. Oiling before installation and again within the first few weeks brings it under control quickly. Unsealed boards can keep bleeding on and off for a year or more.

Does spotted gum decking need oiling?

Yes. Spotted gum still needs an oil finish to protect against UV greying and moisture movement, but it doesn’t need the same urgent tannin-control routine that merbau does.

What’s the price difference between merbau and spotted gum decking?

At Lifetime Pine, spotted gum currently runs about 77 to 80% more per metre than merbau at the same board width. Narrow boards are $5.60/metre (merbau) versus $9.90/metre (spotted gum); wider boards are $10.00/metre (merbau) versus $18.00/metre (spotted gum).

Can I use merbau decking near a pool?

You can, but it’s higher risk. Tannin runoff from unsealed or newly wet merbau can stain light-coloured pool coping and pavers. If the deck is right against the pool edge, spotted gum removes that risk almost entirely.

What width decking board should I choose?

Narrower boards (86 to 90mm) suit smaller decks, curves, and diagonal lays. Wider boards (135 to 140mm) cover a standard rectangular deck faster with fewer joints, and are usually the better buy for a straightforward build.