NCC 2019 Volume Two Amendment 1
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Part 3.9.1 Stairway and ramp construction

Part 3.9.1 Stairway and ramp construction

Appropriate Performance Requirements

Appropriate Performance Requirements

Where an alternative stairway or ramp system is proposed as a Performance Solution to that described in Part 3.9.1, that proposal must comply with—

  1. Performance RequirementP2.5.1; and
  2. the relevant Performance Requirements determined in accordance with A2.2(3) and A2.4(3) as applicable.

3.9.1.0 Explanation of terms

The following figures depict stairway members and associated terminology used to describe them in the Housing Provisions. Some items such as barriers and handrails have been omitted for clarity.

Figure 3.9.1.0 Stairway terms
v2_Fig3910_2016.svg

Explanatory information:

Explanatory information:
  1. Alpine areas:

    The requirements of this Part are to be read in conjunction with Part 3.10.4 where a building is located in an alpine area and contains an external stairway or ramp.

  2. Room heights:

    3.8.2.2 contains the required height for a ceiling above a stairway, ramp or landing, measured vertically above the nosing line of stairway treads or the floor surface of a ramp or landing.

3.9.1.1 Application

Compliance with this acceptable construction practice satisfies Performance Requirement P2.5.1 for stairway and ramp construction.

3.9.1.2 Stairway construction

(a)

A stairway must be designed to take loading forces in accordance with AS/NZS 1170.1 and must have—

(i)

not more than 18 and not less than 2 risers in each flight; and

(ii)

Goings (G), risers (R) and a slope relationship quantity (2R + G) in accordance with Table 3.9.1.1, except as permitted by (b) and (c); and

Table 3.9.1.1 Riser and going dimensions (mm)

Stair type

Riser (R)

Going (G)

Slope relationship

(see Figure 3.9.1.4 below)

(see Figure 3.9.1.4 below)

(2R+G)

Max

Min

Max

Min

Max

Min

Stairs (other than spiral)

190

115

355

240

700

550

Spiral

220

140

370

210

680

590

Note to Table 3.9.1.1: Riser and going dimensions must be measured in accordance with Figure 3.9.1.4.

Figure 3.9.1.4 Riser and going dimensions—Measurement
v2_Fig3912_2005.svg
(iii)

constant goings and risers throughout each flight, except as permitted by (c) and (d), and the dimensions of goings (G) and risers (R) in accordance with (a), (b) and (c) are considered constant if the variation between—

(A)

adjacent risers, or between adjacent goings, is no greater than 5 mm; and

(B)

the largest and smallest riser within a flight, or the largest and smallest going within a flight, does not exceed 10 mm; and

(iv)

risers which do not have any openings that would allow a 125 mm sphere to pass through between the treads; and

(v)

treads of solid construction (not mesh or other perforated material) if the stairway is more than 10 m high or connects more than 3 storeys.

(b)

In the case of a stairway serving only non-habitable rooms, such as attics, storerooms and the like that are not used on a regular or daily basis—

(i)

the going (G), riser (R) and slope relationship quantity (2R + G) in accordance with Table 3.9.1.1 may be substituted with those in Table 3.9.1.2; and

(ii)

need not comply with 3.9.1.2(a)(iv).

Table 3.9.1.2 Riser and going dimensions (mm)—stairways serving non-habitable rooms used infrequently

Riser (R)

Going (G)

Slope relationship

(2R+G)

Max

Min

Max

Min

Max

Min

225

130

355

215

700

540

Note to Table 3.9.1.2: The going (G) must be not more than the tread depth plus a maximum gap of 30 mm between the rear edge of one tread and the nosing of the tread above.

Explanatory information:

Explanatory information:
  1. Not more than 18 and not less than 2 risers:

    3.9.1.2(a)(i) states that a stairway must have not more than 18 and not less than 2 risers in each flight. Where there are less than 2 risers in a flight, it does not comprise a stairway for the purpose of the BCA. 18 risers is considered to be the maximum reasonable number that an average person can negotiate before requiring a rest. Winders are counted as part of the maximum number of 18 risers. More than 1 riser is considered necessary for a person to observe and adjust to a change in level.

  2. Going and riser dimensions:

    The purpose of 3.9.1.2 is to achieve constant going and riser dimensions deemed safe for people to walk up and down. This minimises the risk of people overstepping during descent on uneven stairs (due to short goings) and tripping on ascent (due to high risers). Table 3.9.1.1 and Table 3.9.1.2 express ratios between going and riser dimensions which are considered safe for use. 3.9.1.2(a)(iii) accounts for conditions such as movement of materials due to atmospheric moisture changes or minor deviations related to variations in materials which affect finished stair dimensions.

    Diagram a illustrates adjacent risers within a flight with minor deviations in the materials affecting the finished stair dimensions. The nominated riser height is exceeded by riser A. As a consequence riser height B is less than the nominated riser height. The difference between riser A and riser B cannot exceed 5 mm.

    Diagram b illustrates an entire flight with minor deviations in the materials affecting the finished riser dimensions. In addition to the 5 mm difference permitted between adjacent goings or risers, the maximum difference between the smallest and largest going or riser within a flight must not exceed 10 mm.

    Despite the deviations shown in both Diagram a and Diagram b, the stairs in the flight are deemed constant.

    Irrespective of any minor deviations permitted by 3.9.1.2(a)(iii), finished going and riser dimensions must not exceed the limitations stipulated in Table 3.9.1.1.

Minor deviations in a stairway

Diagram a.

Deviation in adjacent risers

v2_Fig3914a_2016.svg

Notes:

  1. A = larger riser of two adjacent risers.
  2. B = smaller riser of two adjacent risers.
  3. This diagram only shows deviations in risers, however the same principle can apply for goings.

Diagram b.

Deviations over a flight

v2_Fig3914b_2016.svg

Notes:

  1. 4. C = largest riser of the flight.
  2. D = smallest riser of the flight.
  3. This diagram only shows deviations in risers, however the same principle can apply for goings.
  1. Openings in stair risers:

    3.9.1.2(a)(iv) allows the use of open riser stairs. However, it limits the openings to 125 mm to minimise the risk of a person (especially a young child) falling through the opening created by the open riser.

  2. Solid treads:

    3.9.1.2(a)(v) specifies a height where solid treads must be used so that people cannot see through them. This minimises the risk of people being affected by vertigo.

(c)

In the case of a stairway with winders—

(i)

a maximum of 3 consecutive winders in lieu of a quarter landing in a flight and a maximum of 6 consecutive winders in lieu of a half landing in a flight; and

(ii)

the going (G) of all winders in lieu of a quarter or half landing may vary from the going of the straight treads within the same flight provided that the going (G) of such winders is constant.

Explanatory information:

Explanatory information:

Stairways with winders:

  1. 3.9.1.2(c) allows the use of winders in stairways. However, 3.9.1.2(c) places a restriction on the number of allowable winders in a stairway flight, this restriction would apply equally to not permit a stairway incorporating a consecutive series of winders in a flight.
  2. This also means the maximum number of consecutive winders in any stairway flight is 6.
(d)

The point of measurement of the going (G) in the slope relationship quantity (2R + G) for tapered treads and treads in spiral stairways as described in Table 3.9.1.1 (see Figure 3.9.1.1a to Figure 3.9.1.1c) must be—

(i)

for tapered treads, other than treads in a spiral stairway—

(A)

not more than 1 m in width, the middle of the unobstructed width of the stairway (see Figure 3.9.1.1b); and

(B)

more than 1 m in width, 400 mm from the unobstructed width of each side of the stairway (see Figure 3.9.1.1c); and

(ii)

for treads in spiral stairways, the point seven tenths of the unobstructed width from the face of the centre pole or support towards the handrail side (see Figure 3.9.1.2a and Figure 3.9.1.2b).

Figure 3.9.1.1 Measurement of slope relationship—Plan view

Diagram a. Stair with 2 flights
v2_Fig3911a_2016.svg
Diagram b. Tapered treads—not more than 1 m wide
v2_Fig3911b_2016.svg
Diagram c. Tapered treads—more than 1 m wide
v2_Fig3911c_2016.svg

Figure 3.9.1.2 Spiral stairs

Diagram a. Measurement for slope relationship
v2_Fig3912a_2016.svg
Diagram b. Measurement of openings in stairs
v2_Fig3912b_2016.svg

3.9.1.3 Ramps

An external ramp serving an external doorway or a ramp within a building must—

(a)

be designed to take loading forces in accordance with AS/NZS 1170.1; and

(b)

have a gradient not steeper than 1:8; and

(c)

be provided with landings complying with 3.9.1.5 at the top and bottom of the ramp and at intervals not greater than 15 m.

Explanatory information:

Explanatory information:

In relation to external ramps, 3.9.1.3 applies to a ramp serving an external door. For the purpose of 3.9.1.3 a driveway is not considered to be a ramp.

3.9.1.4 Slip-resistance

The requirements for slip-resistance treatment to stair treads, ramps and landings are as follows:

(a)

Treads must have—

(i)

a surface with a slip-resistance classification not less than that listed in Table 3.9.1.3 when tested in accordance with AS 4586; or

(ii)

a nosing strip with a slip-resistance classification not less than that listed in Table 3.9.1.3 when tested in accordance with AS 4586.

(b)

The floor surface of a ramp must have a slip-resistance classification not less than that listed in Table 3.9.1.3 when tested in accordance with AS 4586.

(c)

Landings, where the edge leads to the flight below, must have—

(i)

a surface with a slip-resistance classification not less than that listed in Table 3.9.1.3 when tested in accordance with AS 4586, for not less than 190 mm from the stair nosing; or

(ii)

a nosing strip with a slip-resistance classification not less than that listed in Table 3.9.1.3 when tested in accordance with AS 4586.

Table 3.9.1.3 Slip-resistance classification

Application

Dry surface conditions

Wet surface conditions

Ramp not steeper than 1:8

P4 or R10

P5 or R12

Tread surface

P3 or R10

P4 or R11

Nosing or landing edge strip

P3

P4

Explanatory information:

Explanatory information:
  1. To determine the appropriate surface of a tread or the floor surface of a ramp, it is necessary to determine the likely conditions the tread or ramp will be subject to over the life of the building. This can be either dry, wet or both. A dry surface is one that is not normally wet or likely to be made wet other than by an accidental spill. A wet surface is one that is normally wet or likely to be made wet, including areas exposed to the weather.
  2. Under 3.9.1.4(a) stair treads must have a surface or nosing strip which minimises the risk of people slipping and injuring themselves. In each case the surface or nosing must have a slip-resistance classification when tested in accordance with AS 4586. There are two tests (the Wet Pendulum Test or the Oil-Wet Inclining Platform Test) and two conditions (dry or wet) to be considered.
  3. Under 3.9.1.4(b) the floor surface of a ramp must be slip-resistant to minimise the risk of people slipping and injuring themselves. The surface must have a slip-resistance classification when tested in accordance with AS 4586.

3.9.1.5 Landings

Landings must—

(a)

be not less than 750 mm long and where this involves a change in direction, the length is measured 500 mm from the inside edge of the landing (see Figure 3.9.1.3a); and

(b)

have a gradient not steeper than 1:50; and

(c)

be provided where the sill of a threshold of a doorway opens onto a stairway or ramp that provides a change in floor level or floor to ground level greater than 3 risers or 570 mm (see Figure 3.9.1.3b); and

(d)

extend across the full width of a doorway; and

(e)

in the case of a stairway serving only non-habitable rooms, such as attics, storerooms and the like that are not used on a regular or daily basis, the requirements of (a) may be substituted with a minimum length of landing being not less than 600 mm long.

Explanatory information:

Explanatory information:
  1. Purpose of a landing:

    The purpose of a landing is to provide a rest area for people using the stairway or ramp, and to allow the stairway or ramp to change direction if needed.

  2. Minimum landing length:

    The minimum length of a landing allows people using a stairway or ramp to rest, and reduces the risk of people falling more than one flight of stairs.

  3. Maximum grade of 1:50:

    The maximum grade of 1 in 50 required under 3.9.1.5(b) makes sure that the landing is as level as possible, but still allows a slight slope for drainage if necessary.

Figure 3.9.1.3a Landings
v2_Fig3913a_2016.svg
Figure 3.9.1.3b Threshold landing
v2_Fig3913b_2016.svg

3.9.1.6 Thresholds

Where the threshold of a doorway is more than 230 mm above the adjoining surface it must incorporate steps having riser (R) and going (G) dimensions in accordance with 3.9.1.2.