How to build deck stairs

What limits does the NCC set for stairs?

The NCC 2022 Housing Provisions (Table 11.2.2a) set these limits for stairs other than spiral stairs:

Adjacent risers or goings may differ by no more than 5 mm, and within one flight the largest and smallest may differ by no more than 10 mm. Open risers are allowed if no opening lets a 125 mm sphere pass.

How do you work out the stairs?

1. Measure from the ground to the top of the deck.
2. Divide by a riser height inside 115 to 190 mm, and round up to get the number of risers.
3. Divide the height by that number for the actual riser height.
4. Choose a going that puts 2R + G between 550 and 700 mm.

For a 900 mm deck with five risers, each riser is 180 mm. A 250 mm going gives 2R + G = 610 mm, inside the range.

When do you need a handrail?

A handrail is required along at least one side of the flight, for its full length. Its top must be at least 865 mm above the nosings and it must be continuous, with nothing that interrupts a hand sliding along it. The requirement doesn’t apply to a stair giving a change in elevation of less than 1 m, to a landing, or to a winder with a newel post as a handhold.

Where a fall of 1 m or more is possible, the stair also needs a barrier at least 865 mm above the nosings with openings under 125 mm. The deck needs a barrier at least 1 m high in the same situation.

What about landings?

Landings must be at least 750 mm long, measured 500 mm from the inside edge where the direction changes, with a maximum grade of 1:50. A landing of 600 mm is allowed for non-habitable, infrequently used stairs. A doorway needs a landing the full width of the doorway where the level change is more than three risers or 570 mm. A threshold more than 230 mm above the surface needs compliant steps.

How slippery can the treads be?

Tested to AS 4586, stair treads need P3 or R10 when dry and P4 or R11 when wet; nosing strips need P3 dry and P4 wet. Ask the board maker which class its board carries; ModWood, for example, states R11 for Marina and P5 for Xtreme Guard. See pool decking for wet areas.

What size are timber stringers?

WoodSolutions tables stringers from 200 by 38 mm to 300 by 50 mm for stairs up to 1,800 mm wide. A 200 by 38 mm spotted gum F17 stringer spans 2,600 mm and a 300 by 50 mm one spans 4,200 mm. It specifies 12 mm step bolts at no more than 1,350 mm centres. It doesn’t give the number of stringers, so confirm that with your certifier.

Check which NCC edition your state has adopted and whether your deck needs approval. See how to build a deck.

How do you make deck stairs and steps for a deck?

Start from the NCC limits above, then pick a construction method. We found no standard that gives the number or spacing of stringers, so what follows is what suppliers describe.

• Timber Decking Supply Shed, an Australian timber supplier (page dated 1 September 2025), builds ground-level steps from paired 300 by 50 mm stringers spaced up to about 1 m apart, treads of 250 or 300 by 50 mm with a maximum tread length of 900 mm, 75 by 38 mm cleats on two 10 mm galvanised bolts each, and a 75 by 50 mm ledger. It limits these steps to 1 m overall height and wants every riser equal, including the first and last.
• Bunnings sells step kits in one, two and three step sizes. Its video says to mark each step position on the back of the stringer, pre-drill three countersunk holes per tread and screw treads grip side up.
• Trex Australia’s guide uses the stair width divided by the board’s rated span, plus one, to count stringers, with imperial dimensions based on US codes. We don’t use its figures.

For anything above 1 m, or with a balustrade, follow the NCC rules and ask your certifier about the stringers.