Wide boards, two thicknesses
135 mm wide decking gives a deck a broad, generous board line, and we supply it in two thicknesses: 135 x 19 mm, the standard decking thickness, and 135 x 35 mm, a thick board at nearly twice the depth. The width on the deck looks the same; the difference is what is underneath and what the deck is asked to do.
Availability at Sydney Timber Supply
| Profile | Species available | Notes |
|---|---|---|
| 135 x 19 mm | Ironbark, Spotted Gum, Redgum, Gympie Messmate | Per linear metre, random lengths. Priced online, with bulk and preferred lengths by quote |
| 135 x 21 mm | Blackbutt | Blackbutt is supplied at 21 mm rather than 19 mm at this width. Per linear metre, random lengths |
| 135 x 35 mm | Ironbark, Spotted Gum, Redgum, Gympie Messmate | Specialist profile; a 140 x 35 mm width option is available on these products at the same rate |
The thick profile is available in four of our supplier-documented Class 1 species. Blackbutt is the exception at this width: it is supplied as a 135 x 21 mm board, and its thick section is a 140 x 35 mm board rather than 135 x 35 mm.
When 135 x 19 is the right board
Standard 19 mm decking is the default for residential decks on a conventional joist layout. It delivers the wide-board look, uses less timber per linear metre than the thick profile, and most of our 135 mm species are available in it. For most decks, 135 x 19 over correctly spaced joists is the straightforward specification.
When 135 x 35 earns its place
The 35 mm board is a heavier, more substantial section, chosen for jobs that want visual mass at the board edge or extra robustness in the walking surface: think heavy outdoor structures and high-traffic decks, the applications our supplier documents for dense species such as Ironbark. It is a specialist profile with no broad retail presence, so availability is confirmed against supplier stock.
On spans and joist spacing: our supplier documentation does not publish span tables for these profiles, so confirm span tables with your certifier before designing joist centres around board thickness. Do not assume a thicker board permits wider joist spacing without documented engineering for your specific structure.
Practical differences to weigh
- Timber volume and cost. A 35 mm board contains nearly twice the timber of a 19 mm board of the same width, which shows up in the price and in handling weight on site. Dense hardwoods like Ironbark, at a supplier-documented 1106 to 1170 kg/m3 for Grey, make thick boards genuinely heavy.
- Fixing. Both profiles fix with two screws per joist per supplier installation guidance; pre-drilling is standard practice in dense species either way.
- Species choice. If your shortlist is Blackbutt, the wide board is 135 x 21 mm and the thick section is 140 x 35 mm, so the comparison shifts slightly.
- Appearance in service. Once laid, both read as a 135 mm board line; the thick profile is most visible at exposed edges, stair nosings and deck perimeters.
Price both profiles for your deck
Linear metre prices are shown on every product page, so you can compare a standard and a thick board directly and add your metres to the cart. Convert your deck area to linear metres with the timber calculator (the working is explained in the calculator guide), then request a quote for pack quantities, preferred lengths or trade volumes. For narrow-board options, see the 86 x 19 vs 90 x 19 comparison, or browse everything in the decking collection.
Reviewed by the Sydney Timber Supply team. Last updated 25 August 2026.