Our step treads are solid Merbau, F27 KD, in these profiles:

• 240×35mm and 240×45mm — Step Tread / Beam
• 250×50mm — available as a 1.2m tread, and in 1.8m and above
• 290×42mm — solid, select grade, random lengths
• 290×45mm — Handrail / Beam profile, also used as a tread
• 300×50mm — Step Tread / Beam

Several of these are dual-purpose sections, which is why you will see them described as Step Tread / Beam — the same board suits both roles.

Width determines how deep the step is underfoot. 240mm and 250mm suit most domestic stairs; 290mm and 300mm give a deeper, more generous tread often used for entry steps, feature stairs and wider commercial settings.

Thickness affects both feel and how far the tread can span between supports. Our 35mm and 42mm sections are lighter; the 45mm and 50mm sections are noticeably more substantial and are the usual choice where the tread spans further or carries heavier traffic.

The right combination depends on the span between your stringers, the loads and the look you want. Where the stair is structural, have the design confirmed by a suitably qualified building professional.

F27 is a structural strength grade for solid hardwood, indicating the timber has been graded to meet defined structural performance requirements. KD means kiln dried — the timber has been dried under controlled conditions to reduce moisture content and improve dimensional stability.

As natural timber, individual boards can still contain variation in colour and natural characteristics.

Not necessarily. A 250×50 board may be planed down to a slightly thinner finished thickness during machining, to achieve consistent dimensions and surface quality across the batch. If your design depends on an exact finished thickness, check with us before ordering.

Use cup-head bolts with nuts as the primary fixing method. This is the single most important thing you can do to avoid cracking a tread.

Merbau is dense, and a bolt through a properly sized hole lets the timber sit without being drawn hard against the steel.

Coach screws fixed up through the stringer into the underside of the tread are a common cause of cracking. They pull the timber down hard onto the steel, and because they are easy to over-tighten, the load concentrates in a small area of a dense board that wants to move seasonally.

Use cup-head bolts and nuts instead, and tighten only as much as needed to secure the tread — no further.

Yes — seal all sides before installation, including the ends and the underside. This is easy to skip because those faces will not be seen, and it is the most common installation mistake we see.

An unsealed underside or end grain lets moisture in and out at a different rate to the sealed top face, and that imbalance is what causes cupping, movement and splitting later. Sealing every face lets the board move evenly.

• Allow for movement of steel components. Timber and steel expand and contract at different rates — the fixing detail needs to accommodate that rather than lock the tread rigidly in place.
• Support longer spans adequately. A tread spanning further between stringers will flex more; add intermediate support where needed.
• Drainage and ventilation matter outdoors. Water sitting on or under a tread is what shortens its life.

Yes. We stock hot-dip galvanised steel stair stringers from 1 step through to 17 steps, supplied as a pair (2 pieces) — so one product covers both sides of the stair.

• Concrete-In — the base of the stringer is set into a concrete footing as it is poured. Suited to new work where the footing is going in at the same time.
• Bolt-On Concrete — the stringer bolts down onto an existing concrete slab or footing. Suited to retrofitting stairs to a surface that is already there.

Both are hot-dip galvanised. Which you need depends on whether your footing already exists.

Count the number of treads, not the total rise. Measure the vertical height from the finished lower surface to the finished upper surface, and work out how many risers that divides into at a comfortable, consistent step height — then order the stringer pair for that number of steps.

Riser heights and tread depths for stairs are regulated, so confirm your dimensions against the applicable building requirements before ordering.

Yes, if left unfinished outdoors. Merbau starts a rich reddish-brown and will silver off over time with sun and weather exposure. If you want to hold the original tone, a suitable timber oil applied on installation and maintained periodically is the usual approach — see our oils and stains range.

Merbau also contains natural tannins that can leach and stain adjacent surfaces in early rain events. Sealing before installation helps, and any staining on concrete can usually be cleaned with a suitable tannin remover.

Yes. Merbau step treads are used for both internal and external stairs. Indoors the timber is protected from weather and holds its colour far longer, so it tends to stay close to its original tone with much less maintenance.

Browse the full Decking Wood QLD range of step treads, stair stringers, decking, hardware and coatings.