Stair and balustrade rules under SANS 10400-M

Stairs cause more falls than almost any other part of a house, and the rules in SANS 10400-M are there to make every step predictable. This guide sets out those rules for stairs and their balustrades, then works through a typical staircase so you can see how they fit together.

The steps

• Rise: no step may rise more than 200 mm (4.2.5).
• Going: the going (the horizontal depth of a tread) and the width of any tread must be at least 250 mm (4.2.6). Where risers are open, each tread must overlap the one below by at least 25 mm.
• 2R + G: twice the rise plus the going must be between 570 and 650 mm (4.2.8). This keeps the step comfortable to walk.
• Consistency: the risers and goings in a flight may not vary by more than 6 mm (4.2.7). An odd step is the one people trip on.
• Winders: tapered treads are measured 400 mm from the narrow end, where the going must be at least 125 mm (4.2.9).

Measuring the total rise

Measure the rise from finished floor to finished floor, including the tiles, screed or timber that will go on top of each slab. A stair set out on bare concrete and then tiled at the top but not the bottom ends up with one odd step.

The flight

• Headroom: at least 2.1 m, measured from the pitch line (4.2.1).
• Width: at least 750 mm (4.2.1).
• Landings: no flight may rise more than 3 m without a landing (4.2.3), and a landing between two flights in a straight line must be at least 900 mm long and as wide as the flight (4.2.2).

Balustrades and handrails

• A flight with more than three risers needs protection on both sides at least 1 m high (4.3.1).
• In houses, no opening above the pitch line may let a 100 mm ball through, so balusters must be close enough together.
• A flight with more than five risers needs at least one continuous handrail along its full length (4.3.2), fixed 850 mm to 1 m above the pitch line, on one side of a flight narrower than 1.1 m and on both sides of a wider one (4.3.3).
• The handrail rule does not apply to a dwelling house on its own site (occupancy class H4), or inside an individual dwelling unit where two or more units share a site (class H3); SANS 10400-A defines the classes. Fit one anyway: a handrail on a long flight is good practice in any home, and the balustrade rule above still applies.

Worked example

A floor-to-floor height of 2,600 mm, with the maximum rise of 200 mm:

1. Risers = 2,600 ÷ 200 = 13 risers of exactly 200 mm.
2. Treads = risers − 1 = 12 treads.
3. With a 250 mm going, 2R + G = 2 × 200 + 250 = 650 mm, right at the upper limit, so the step is allowed. A going of 260 mm would give 660 mm, which is over the limit. With a 200 mm rise, the going must be exactly 250 mm to satisfy both rules, so a lower rise gives more freedom.
4. The total going is 12 × 250 = 3.0 m, and the stair rises at about 38.7°.
5. The flight rises 2.6 m, under the 3 m limit, so no landing is needed.
6. Thirteen risers is more than three, so protection at least 1 m high is needed on both sides. It is also more than five, so a handrail is required, unless the stair is in a dwelling house or inside a dwelling unit; even then, fit one.

Try the same stair with 14 risers: 2,600 ÷ 14 = 185.7 mm each. Now 2R + G stays within 570 to 650 mm for any going from 250 mm (the minimum) up to about 279 mm, so a comfortable 260 mm going works (2 × 185.7 + 260 = 631 mm), though the stair gets longer. The stair calculator checks every one of these rules as you change the numbers.

Balusters

To keep the gaps under 100 mm, the number of balusters per section = (rail length − gap) ÷ (baluster width + gap), rounded up. The baluster spacing calculator spaces them evenly between posts. For ramps instead of steps, SANS 10400-S sets the gradients and landings; see the ramp calculator.

This guide is general information for estimating. It is not engineering, legal or tax advice. Check SANS 10400 (the National Building Regulations) and your local municipality’s building control officer for your project.