Spotted Gum Timber Decking

Spotted Gum decking in 86 × 19 mm and 135 × 19 mm: a dense Australian hardwood with Class 1 durability above ground, Janka hardness 10.1 kN and a place on the AS 3959 bushfire-resisting timber list, so it can be used for decking up to BAL-29.

• Sizes and lengths: 86 × 19 mm and 135 × 19 mm in random lengths, plus 135 × 19 mm long lengths of 5.7–6.0 m for fewer joins
• Timber: Spotted Gum (Corymbia maculata, C. citriodora and C. henrii), grown from north-east Victoria to Queensland; light brown to dark red-brown; about 990–1010 kg/m³
• Durability: Class 1 above ground, which the Queensland Government rates at more than 40 years’ expected life; Class 2 in-ground; the heartwood is termite resistant
• Tannin: WoodSolutions says Spotted Gum is less prone to tannin bleed than other species
• Bushfire: on the AS 3959 list of bushfire-resisting timbers, so it can be used for decking up to BAL-29 (BAL-40 and Flame Zone need tested systems)
• Joist spacing: 450 mm centres, as WoodSolutions recommends for decking; its deck design guide allows up to 500 mm for 19 mm hardwood, or 350 mm if the boards run at 45°
• Gaps: 3–4 mm between 86 mm boards and 4–5 mm between 135 mm boards at installation (WoodSolutions deck design guide)
• How much for a deck: a 20 m² deck needs about 140 lineal metres of 135 mm board or about 225 lineal metres of 86 mm, plus about 10% for offcuts
• Low decks: under 400 mm off the ground, WoodSolutions suggests 5–6 mm gaps and at least 40 mm between the deck and the house, for airflow
• Fixing: two fixings per board at every joist, at least 12 mm from edges and ends. Pre-drill this dense hardwood. Use stainless steel within 1 km of the coast or 1 m of a pool. See our decking screws
• Finishing: coat every face and cut end, ideally before fixing, then recoat at least once a year or as the oil maker directs (WoodSolutions); left bare, it weathers to silver-grey. Oils we stock: CUTEK CD50, Intergrain Universal Timber Oil or Sceney’s Timber Decking Oil
• At Greenhill: stocked at 170 Settlement Road, Thomastown, with pickup or delivery across Melbourne and regional Victoria. Compare species on our hardwood decking page.

Using Spotted Gum inside as well? See Spotted Gum flooring.

Spotted Gum decking: sizes, lengths and prices

Random lengths are the usual way to buy it and the cheapest per metre: packs run from about 1.8 m up to 5.4 m and you cut to suit. The 135 × 19 mm long-length boards are 5.7–6.0 m pieces for decks where you want a run with no joins. Prices are our website prices on 14 October 2026 and are per lineal metre unless marked per board; a 20 m² deck needs about 140 lineal metres of 135 mm board or 225 of 86 mm, plus 10% for cuts.

What Spotted Gum decking is like

Spotted Gum is the hardwood most Melbourne builders reach for when a customer wants an Australian species rather than Merbau. It is a group of three closely related trees, Corymbia maculata, C. citriodora and C. henryi, cut from Queensland down to the NSW south coast. The boards run from pale brown to a dark red-brown, often in the same pack, with a wavy grain that shows the figure once it is oiled. At about 990 kg/m³ seasoned it is heavy; a 5.4 m length of 135 × 19 weighs around 14 kg.

WoodSolutions puts its seasoned hardness at 10.1 kN, above Blackbutt (8.9) and Merbau (8.5), and rates the heartwood durability Class 1 above ground and Class 2 in the ground, with natural termite resistance. It is also the lowest-bleed hardwood we sell: WoodSolutions describes it as less prone to tannin bleed than other species, so it is the safer pick next to pale paving or render. The sapwood can be attacked by lyctid borer, which is why decking is cut from heartwood.

Where it suits

Spotted Gum is on the AS 3959 list of bushfire-resisting timbers, so at 19 mm it can be used for decking up to BAL-29 without any treatment; BAL-40 and Flame Zone need a tested system. That, the hardness and the low bleed make it the all-round choice: house decks, pool surrounds, steps and commercial outdoor areas. The one place we would steer you elsewhere is a deck that stays wet and shaded most of the year, where grey ironbark or Grey Box, both Class 1 in the ground as well, give more margin.

Fixing and finishing

Pre-drill every fixing: at this density screws will snap or split the board end otherwise. Use two stainless or Class 3 galvanised screws per board at each joist, 450 mm joist centres, and a 4–5 mm gap on the 135 mm board (3–4 mm on 86 mm). Coat all faces and cut ends before laying, then once or twice a year. The CUTEK Extreme CD50 and Intergrain Universal Timber Oil on our shelves both suit it; left bare it silvers within a year. Screws, joist tape and stirrups are in decking accessories.

The same timber for other jobs

• Spotted Gum flooring – solid, engineered, hybrid and laminate floors in the same timber
• NSW Spotted Gum solid floorboards – 83 × 14, 130 × 14 and 130 × 19 mm
• QLD Spotted Gum solid floorboards
• Hardwood decking – all six species side by side

Compare the species

Our decking timber comparison puts hardness, durability, bushfire rating and price per metre for all six hardwoods on one page; Merbau decking is the budget alternative.

Questions we get asked

How much does Spotted Gum decking cost?

On our website on 14 October 2026, 86 × 19 mm random lengths are $9.60 per lineal metre and 135 × 19 mm $16.50 per lineal metre, so a 20 m² deck is roughly $2,400–$2,550 in boards including 10% for cuts, before fixings and oil.

Is Spotted Gum better than Merbau for decking?

It is harder (10.1 kN against 8.5), bleeds far less tannin, and is Australian-grown; Merbau is cheaper per metre and comes in more widths. Both are Class 1 above ground and both are BAL-29 timbers.

Can I use Spotted Gum decking in a BAL-29 area?

Yes. It is on the bushfire-resisting timber list in AS 3959, so 19 mm boards can be used for decking up to BAL-29. BAL-40 and Flame Zone need a tested deck system.

What colour does it go?

Oiled, the boards keep their light-brown to red-brown range and the grain shows. Left uncoated it weathers to silver-grey in about a year and can be brought back with a deck cleaner and oil.

Does it need pre-drilling?

Yes, every screw. It is dense enough to shear screws and split board ends if you drive straight in.

Pickup and delivery

Stocked at 170 Settlement Road, Thomastown, Mon–Fri 7 am–4:30 pm and Sat 9 am–1 pm. We pack and load it for you, or deliver across Melbourne and regional Victoria; delivery is quoted with the order. Call (03) 9465 9875 with your sizes and we will work out the lineal metres and the price.

Pick up from 170 Settlement Road, Thomastown. Stocked lines are usually ready the same day. Delivery across Melbourne and regional Victoria is quoted on the order; call (03) 9465 9875 for a price on your suburb.

All prices include GST. Flooring is priced per square metre, decking and dressed timber per lineal metre, framing and posts per length. Trade accounts get trade pricing on the site and at the counter: apply here.

Bring your room or deck sizes in, or call (03) 9465 9875, and we will work out boards, lengths, fixings and oil, with about 10% allowed for cuts.