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:
| Measure | Limit |
|---|---|
| Riser height | 115 to 190 mm |
| Going | 240 to 355 mm |
| 2R + G | 550 to 700 mm |
| Risers per flight | 2 to 18 |
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?
- Measure from the ground to the top of the deck.
- Divide by a riser height inside 115 to 190 mm, and round up to get the number of risers.
- Divide the height by that number for the actual riser height.
- 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.
Questions
What are the NCC rules for deck stairs?
Risers 115 to 190 mm, goings 240 to 355 mm, 2R + G between 550 and 700 mm, and 2 to 18 risers per flight under NCC 2022. Open risers may not let a 125 mm sphere through.
Do deck stairs need a handrail?
Yes, on at least one side, unless the stair gives a change in elevation of less than 1 m. The top of the handrail must be at least 865 mm above the nosings, and the rail must be continuous.
How much can risers differ?
Adjacent risers or goings may differ by no more than 5 mm, and within a flight the largest and smallest may differ by no more than 10 mm.
How many stringers do deck stairs need?
We haven't found a source that gives a number or spacing. WoodSolutions tables stringer sizes and spans only, so ask your certifier or the maker of your stair system.