Two common narrow decking profiles
86 x 19 mm and 90 x 19 mm are the two narrow decking widths in our range, and they rarely compete head to head, because at Sydney Timber Supply the width largely follows the species. 86 x 19 is the narrow profile for our Australian hardwoods; 90 x 19 is the profile for Merbau, Jambu and Jambu Mixed. Choosing between the widths is therefore mostly choosing between timbers.
Which species come in which width
| Profile | Species available at STS | Selling unit |
|---|---|---|
| 86 x 19 mm | Ironbark, Spotted Gum, Blackbutt, Redgum, Gympie Messmate | Per linear metre, random lengths. Priced online, with bulk and preferred lengths by quote |
| 90 x 19 mm | Merbau, Jambu, Jambu Mixed | Per linear metre. Priced online, with bulk and preferred lengths by quote |
So if you want a QLD Class 1 Hardwood such as Ironbark or Spotted Gum in a narrow board, 86 x 19 is the profile. If you want Merbau or Jambu, the narrow board is 90 x 19. Wider boards are covered separately in our 135 mm profile comparison.
How the width changes your quantities
Board width plus the ventilation gap gives the cover width, and cover width drives how many linear metres a deck needs. As an illustration, take a 20 m2 deck at the 4 mm gap our timber calculator assumes:
- 86 x 19 at a 90.0 mm cover width: 20 divided by 0.090 = about 222 lm before wastage
- 90 x 19 at a 94.0 mm cover width: 20 divided by 0.094 = about 213 lm before wastage
The wider board covers the same deck with roughly 4 percent fewer linear metres and fewer fixing rows, while the narrower board gives a finer, more closely striped deck surface. Always run your own numbers with your product's specified gap: the timber calculator does the conversion and shows the working, and the calculator guide explains each step.
Practical points when choosing
- Species first. Durability, colour and budget differences between the timbers will matter far more to the finished deck than 4 mm of board width. Compare species in the hardwood comparison table.
- Fixings scale with board count. Boards are fixed with two screws per joist per supplier installation guidance, so a deck in narrower boards carries more fixings for the same area.
- Matching existing decking. If you are extending or repairing a deck, match the existing cover width; mixing 86 and 90 mm boards in one surface will not line up.
- Both need the same care. Whatever the width, correct gaps, ventilation, sealed cut ends and a maintained oil finish are what keep the deck healthy.
Compare both if you are undecided
Linear metre prices are shown on every product page, so you can price an 86 x 19 Australian hardwood against a 90 x 19 Merbau or Jambu option directly and add your metres to the cart. For pack quantities, preferred lengths or trade volumes, request a quote with your deck area and both options, or browse the full decking collection first.
Reviewed by the Sydney Timber Supply team. Last updated 25 August 2026.