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Part 3.9.1 Stairway and ramp construction

3.9.1.0 Explanation of terms

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

Figure 3.9.1.0 Stairway terms
Show Full Sized ImageFigure 3.9.1.0 Stairway terms
Explanatory information:
  1. Alpine areas:

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

  2. Room heights:

    Open link in same page3.8.2.2 contains the Open link in same pagerequired height for a ceiling above a stairway, ramp or Open link in same pagelanding, measured vertically above the nosing line of stairway treads or the floor surface of a ramp or Open link in same pagelanding.

Acceptable Construction Practice

3.9.1.1 Application

Compliance with this acceptable construction practice satisfies Open link in same pagePerformance Requirement Open link in same pageP2.5.1 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 Open link in same pagerisers in each Open link in same pageflight; and

(ii)

Open link in same page Goings (G), Open link in same pagerisers (R) and a slope relationship quantity (2R + G) in accordance with Open link in same pageTable 3.9.1.1, except as permitted by Open link in same page(b) and Open link in same page(c); and

Table 3.9.1.1 Riser and going dimensions (mm)

Stair type

Riser (R)

Going (G)

Slope relationship

(see Open link in same page Figure 3.9.1.4 below)

(see Open link in same page 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 Open link in same page Table 3.9.1.1 : Open link in same page Riser and Open link in same pagegoing dimensions must be measured in accordance with Open link in same pageFigure 3.9.1.4.

Figure 3.9.1.4 Riser and going dimensions—Measurement
Show Full Sized ImageFigure 3.9.1.4 Riser and going dimensions—Measurement
(iii)

constant Open link in same pagegoings and Open link in same pagerisers throughout each Open link in same pageflight, except as permitted by Open link in same page(c) and Open link in same page(d), and the dimensions of Open link in same pagegoings (G) and Open link in same pagerisers (R) in accordance with Open link in same page(a), Open link in same page(b) and Open link in same page(c) are considered constant if the variation between—

(A)

adjacent Open link in same pagerisers, or between adjacent Open link in same pagegoings, is no greater than 5 mm; and

(B)

the largest and smallest Open link in same pageriser within a Open link in same pageflight, or the largest and smallest Open link in same pagegoing within a Open link in same pageflight, does not exceed 10 mm; and

(iv)

Open link in same page 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-Open link in same pagehabitable rooms, such as attics, storerooms and the like that are not used on a regular or daily basis—

(i)

the Open link in same pagegoing (G), Open link in same pageriser (R) and slope relationship quantity (2R + G) in accordance with Open link in same pageTable 3.9.1.1 may be substituted with those in Open link in same pageTable 3.9.1.2; and

(ii)

need not comply with Open link in same page3.9.1.2(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 Open link in same page Table 3.9.1.2 : The Open link in same pagegoing (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:
  1. Not more than 18 and not less than 2 risers:

    Open link in same page3.9.1.2(a)(i) states that a stairway must have not more than 18 and not less than 2 Open link in same pagerisers in each Open link in same pageflight. Where there are less than 2 Open link in same pagerisers in a Open link in same pageflight, it does not comprise a stairway for the purpose of the BCA. 18 Open link in same pagerisers 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 Open link in same pagerisers. More than 1 Open link in same pageriser is considered necessary for a person to observe and adjust to a change in level.

  2. Going and riser dimensions:

    The purpose of Open link in same page3.9.1.2 is to achieve constant Open link in same pagegoing and Open link in same pageriser 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 Open link in same pagegoings) and tripping on ascent (due to high Open link in same pagerisers). Open link in same pageTable 3.9.1.1 and Open link in same pageTable 3.9.1.2 express ratios between Open link in same pagegoing and Open link in same pageriser dimensions which are considered safe for use. Open link in same page3.9.1.2(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.

    Open link in same pageDiagram a illustrates adjacent Open link in same pagerisers within a Open link in same pageflight with minor deviations in the materials affecting the finished stair dimensions. The nominated Open link in same pageriser height is exceeded by Open link in same pageriser A. As a consequence Open link in same pageriser height B is less than the nominated Open link in same pageriser height. The difference between Open link in same pageriser A and Open link in same pageriser B cannot exceed 5 mm.

    Open link in same pageDiagram b illustrates an entire Open link in same pageflight with minor deviations in the materials affecting the finished Open link in same pageriser dimensions. In addition to the 5 mm difference permitted between adjacent Open link in same pagegoings or Open link in same pagerisers, the maximum difference between the smallest and largest Open link in same pagegoing or Open link in same pageriser within a Open link in same pageflight must not exceed 10 mm.

    Despite the deviations shown in both Open link in same pageDiagram a and Open link in same pageDiagram b, the stairs in the Open link in same pageflight are deemed constant.

    Irrespective of any minor deviations permitted by Open link in same page3.9.1.2(a)(iii), finished Open link in same pagegoing and Open link in same pageriser dimensions must not exceed the limitations stipulated in Open link in same pageTable 3.9.1.1.

  3. Minor deviations in a stairway

    Diagram a.

    Deviation in adjacent risers

    Notes:

    1. A = larger Open link in same pageriser of two adjacent Open link in same pagerisers.
    2. B = smaller Open link in same pageriser of two adjacent Open link in same pagerisers.
    3. This diagram only shows deviations in Open link in same pagerisers, however the same principle can apply for Open link in same pagegoings.

    Diagram b.

    Deviations over a flight

    Notes:

    1. 4. C = largest Open link in same pageriser of the Open link in same pageflight.
    2. D = smallest Open link in same pageriser of the Open link in same pageflight.
    3. This diagram only shows deviations in Open link in same pagerisers, however the same principle can apply for Open link in same pagegoings.
    1. Openings in stair risers:

      Open link in same page3.9.1.2(a)(iv) allows the use of open Open link in same pageriser 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 Open link in same pageriser.

    2. Solid treads:

      Open link in same page3.9.1.2(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 Open link in same pagewinders

(i)

a maximum of 3 consecutive Open link in same pagewinders in lieu of a quarter Open link in same pagelanding in a Open link in same pageflight and a maximum of 6 consecutive Open link in same pagewinders in lieu of a half Open link in same pagelanding in a Open link in same pageflight; and

(ii)

the Open link in same pagegoing (G) of all Open link in same pagewinders in lieu of a quarter or half Open link in same pagelanding may vary from the Open link in same pagegoing of the straight treads within the same Open link in same pageflight provided that the Open link in same pagegoing (G) of such Open link in same pagewinders is constant.

Explanatory information:

Stairways with winders:

  1. Open link in same page3.9.1.2(c) allows the use of Open link in same pagewinders in stairways. However, Open link in same page3.9.1.2(c) places a restriction on the number of allowable Open link in same pagewinders in a stairway Open link in same pageflight, this restriction would apply equally to not permit a stairway incorporating a consecutive series of Open link in same pagewinders in a Open link in same pageflight.
  2. This also means the maximum number of consecutive Open link in same pagewinders in any stairway Open link in same pageflight is 6.
(d)

The point of measurement of the Open link in same pagegoing (G) in the slope relationship quantity (2R + G) for Open link in same pagetapered treads and treads in Open link in same pagespiral stairways as described in Open link in same pageTable 3.9.1.1 (see Open link in same pageFigure 3.9.1.1a to Open link in same pageFigure 3.9.1.1c) must be—

(i)

for Open link in same pagetapered treads, other than treads in a Open link in same pagespiral stairway

(A)

not more than 1 m in width, the middle of the unobstructed width of the stairway (see Open link in same pageFigure 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 Open link in same pageFigure 3.9.1.1c); and

(ii)

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

Figure 3.9.1.1 Measurement of slope relationship—Plan view

Diagram a. Stair with 2 flights
Show Full Sized ImageFigure 3.9.1.1 Measurement of slope relationship—Plan view - Diagram a. Stair with 2 flights
Diagram b. Tapered treads—not more than 1 m wide
Show Full Sized ImageFigure 3.9.1.1 Measurement of slope relationship—Plan view - Diagram b. Tapered treads—not more than 1 m wide
Diagram c. Tapered treads—more than 1 m wide
Show Full Sized ImageFigure 3.9.1.1 Measurement of slope relationship—Plan view - Diagram c. Tapered treads—more than 1 m wide

Figure 3.9.1.2 Spiral stairs

Diagram a. Measurement for slope relationship
Show Full Sized ImageFigure 3.9.1.2 Spiral stairs - Diagram a. Measurement for slope relationship
Diagram b. Measurement of openings in stairs
Show Full Sized ImageFigure 3.9.1.2 Spiral stairs - Diagram b. Measurement of openings in stairs

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 Open link in same pagelandings complying with Open link in same page3.9.1.5 at the top and bottom of the ramp and at intervals not greater than 15 m.

Explanatory information:

In relation to external ramps, Open link in same page3.9.1.3 applies to a ramp serving an external door. For the purpose of Open link in same page3.9.1.3 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 Open link in same pagelandings are as follows:

(a)

Treads must have—

(i)

a surface with a slip-resistance classification not less than that listed in Open link in same pageTable 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 Open link in same pageTable 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 Open link in same pageTable 3.9.1.3 when tested in accordance with AS 4586.

(c)

Open link in same page Landings , where the edge leads to the Open link in same pageflight below, must have—

(i)

a surface with a slip-resistance classification not less than that listed in Open link in same pageTable 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 Open link in same pageTable 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:
  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 Open link in same page3.9.1.4(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 Open link in same page3.9.1.4(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

Open link in same page 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 Open link in same pagelanding (see Open link in same pageFigure 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 Open link in same pageFigure 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-Open link in same pagehabitable rooms, such as attics, storerooms and the like that are not used on a regular or daily basis, the requirements of Open link in same page(a) may be substituted with a minimum length of Open link in same pagelanding being not less than 600 mm long.

Explanatory information:
  1. Purpose of a landing:

    The purpose of a Open link in same pagelanding 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 Open link in same pagelanding allows people using a stairway or ramp to rest, and reduces the risk of people falling more than one Open link in same pageflight of stairs.

  3. Maximum grade of 1:50:

    The maximum grade of 1 in 50 Open link in same pagerequired under Open link in same page3.9.1.5(b) makes sure that the Open link in same pagelanding is as level as possible, but still allows a slight slope for drainage if necessary.

Figure 3.9.1.3a Landings
Show Full Sized ImageFigure 3.9.1.3a Landings
Figure 3.9.1.3b Threshold landing
Show Full Sized ImageFigure 3.9.1.3b Threshold landing

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 Open link in same pageriser (R) and Open link in same pagegoing (G) dimensions in accordance with Open link in same page3.9.1.2.