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Stair construction for Class 1 buildings

This information sets out the requirements under National Construction Code (NCC) Volume Two – Housing Provisions for stair construction in Class 1 residential buildings.

In this article

  • Stair construction in residential buildings
  • Stair tolerances

Stair construction in residential buildings

The National Construction Code (NCC)  Volume Two – Housing Provisions contains provisions for stair construction in Class 1 buildings. Note that there are no Australian Standards for residential stair construction. 

All stairs must comply with the NCC Performance Requirements. This can be achieved by building a stair in accordance with the Deemed-to-Satisfy Provisions set out in the NCC that requires: 

  • Each flight must have no more than 18 or less than two risers. A flight of stairs is defined as a constant series of risers including winders that is not interrupted by a landing. A single riser creating a change of level does not fit the definition of ‘flight’. 
  • A maximum of three winders in lieu of a quarter landing and six winders in lieu of half landings. The length of a flight is limited to restrict the distance a person could fall down the stair. Quarter landings are considered sufficient to halt a person’s fall and are not part of a flight. Winders will not halt a person’s fall and therefore are counted as part of a flight. 
  • Dimensions of goings and risers must be constant throughout each flight . The riser and going dimensions for each flight of conventional stairs are as shown in Table 1. The actual dimensions must not exceed the minimum and maximum for each of the R, G and 2R+G. 
Table 1 (extract from the NCC Volume Two)
Riser and going dimension (mm) for private stairways
Riser (R)  Going (G) Slope relationship (2R+G)
Max Min Max Min Max Min
Conventional stairs 190 115 355 240 700 550

Note: BCA Volume One has a minimum going of 250mm for public stairways.


Stair construction for Class 1 buildings

  • The above requirements are for conventional stair flights and the BCA should be consulted for dimension and construction for spiral stairs and tapered treads. 
  • Where a doorway opens onto a stair and the change in level is greater than 570mm (three risers of 190mm each) a landing not less than 750mm long must be provided as shown in Figure from NCC 2019. 

Stair construction for Class 1 buildings

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Stair tolerances

The purpose of NCC stair riser and going dimensions is to achieve constant stair tread 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). 

However, NCC clause 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.

Some state governments (including NSW and Victoria) have also published specific documents that may be used by the builder and the consumer to gauge tolerances for some building matters. The guides all includes tolerances for stair construction. HIA also publishes the Guide to Materials and Workmanship for Residential Building Work [LINK to the new page relating to the Guide], which provides a tolerance for stair construction. 

A tolerance of up to 5mm from the nominated dimensions in the contract documents is considered acceptable to allow for the variation in behaviour of timber caused by atmospheric moisture changes. This would generally relate to external stairs. 

The top and bottom risers may be varied to allow for the installation of floor finishes nominated in the contract documents. This variation is to provide uniform and constant riser height throughout the stair after installation of the nominated floor finishes. This also applies to first and last risers of concrete stairs. This tolerance is not to be applied to allow for poor construction practice. 

To find out more, contact HIA’s Building Services team.

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