Merbau
Merbau: a dense tropical hardwood widely used for decking in Australia. Durability Class 1 above-ground, Janka 8.5 kN. Available as 90x19 and 140x19 mm boards.
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Merbau (botanical name Intsia bijuga) is a dense tropical hardwood native to Southeast Asia and the Pacific Islands, widely used for residential decking in Australia. It is rated Durability Class 1 for above-ground use under AS 5604:2022, meaning the heartwood has very high natural resistance to decay and insect attack without the need for chemical treatment.
Common deck board sizes in Australia are 90 x 19 mm and 140 x 19 mm. Merbau has a Janka hardness of approximately 8.5 kN, making it highly resistant to surface wear. A key characteristic: merbau bleeds red-brown tannins when first wet, which can stain surrounding concrete and paving. Pre-washing boards with an oxalic-acid cleaner two or three times before installation is standard practice to minimise tannin bleed.
Also known as: kwila, Pacific maple, Intsia bijuga
Category: Timber species, decking material
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Last updated: 2026-05-08. Verified: 2026-05-08.