Stairs and Balustrades Under NCC Part H5 for Australian Homes

What it is

Stair and balustrade compliance for Class 1 residential buildings is covered by NCC 2022 Volume Two Part H5 Safe Movement and Access. The Deemed-to-Satisfy provisions sit in the ABCB Housing Provisions Part 11. Together they set the geometry of stairs, the height and opening rules for balustrades, and the handrail requirements.

These provisions exist to stop falls. A stair that fails the rise and going test is a trip hazard before the house is even handed over. A balustrade with gaps larger than 125 mm fails the children-falling test. Both items show up on practical completion inspections and both attract defect notices that are expensive to retrofit.

Stair geometry

Riser and going

For private stairs in Class 1 buildings the Housing Provisions set riser (R) and going (G) ranges. Riser is the vertical face. Going is the horizontal tread depth. The DTS limits are R between 115 mm and 190 mm, G between 240 mm and 355 mm, and the slope relationship 2R plus G between 550 mm and 700 mm.

For non-habitable stairs (such as stairs to a basement storage or to a Class 10 deck) the limits widen slightly: R 130 mm to 225 mm and G 215 mm to 355 mm.

Uniformity is the trap. All risers in the same flight must be within plus or minus 5 mm of each other, and all goings within plus or minus 5 mm. A single odd step from a site setout error fails the lot.

Flight length and landing

A flight has no more than 18 risers and no fewer than 2. A landing breaks longer flights and is required where the door at the top opens over the stair. Landings have a minimum dimension in the direction of travel.

Nosing and slip resistance

The going is measured along the nosing line. Nosings on external stairs need a slip-resistant finish that meets the relevant classification in the Housing Provisions, typically P3 or R10 for external use.

Balustrades

A balustrade is required wherever the fall is more than 1 metre to the surface below. That covers stairs, landings, balconies, decks, mezzanines and external stairs.

Height

Balustrade height is at least 865 mm above the stair nosing line, and 1 metre above floors of balconies, decks and landings. Where the deck or balcony is 4 metres or more above the ground, the balustrade is at least 1 metre and there are further opening size limits.

Openings

Any opening in a balustrade has to refuse a 125 mm sphere. That covers gaps between balusters, gaps at the bottom rail and gaps at the top rail. For balconies and decks more than 4 metres above ground, there is also a no-climb zone: between 150 mm and 760 mm above the floor no horizontal members may be present that a child could use as a step.

Handrails

A handrail is required on at least one side of a stair flight with four or more risers. The handrail is between 865 mm and 1 metre above the stair nosing line, continuous across the flight, and has end terminations that do not catch on clothing.

Where stairs and balustrades fail an inspection

Stair geometry out of tolerance

The bottom riser is shorter than the others because the slab finish was poured higher than expected. The top going is shorter because the joists were doubled up. Each of these is a measurement defect picked up with a tape and a level.

Balustrade gaps

Vertical balusters at 130 mm gaps will pass a glance but fail a sphere test. Horizontal slat balustrades with 100 mm gaps may pass the gap test but breach the no-climb zone on a high deck.

Missing handrails

A handrail on the wall side only when the stair has open exposure on the other side. A handrail that stops short of the bottom riser. Both are common on owner-builder jobs and on remedial work.

Glass balustrade compliance

Frameless glass balustrades have to be Grade A safety glass and comply with AS 1288. The certification labels need to remain visible on each panel until handover. The auditor checks the label and the fixing detail.

Inspection hold points

The hold points for stairs are framing completion, finish installation, and balustrade installation. The auditor uses a tape, a level, a sphere gauge and a torque wrench on glass fixings. The geometry check is mechanical. The balustrade check uses the sphere and the no-climb measurement.

Why an auditor cares

Falls from stairs and balconies are a major source of residential injury and a recurring builder liability. The audit pattern is consistent. Are the risers and goings uniform and within range. Is the balustrade tall enough. Does it refuse the sphere. Is the no-climb zone clear on high balconies. Is the handrail continuous and at the right height.

Each of those traces to a Part H5 or Housing Provisions Part 11 clause, and each defect has a tape-measure answer.