Stair Compliance in Residential Buildings
Why AS1428.1 stairs are still needed in residential buildings with lifts...?
When a Class 2 building includes a compliant lift or ramp the BCA access requirements of Table D3.1 increase. Instead of just needing access from the main entry to the entry doors of SOU units on one floor and each type of common-use room/space in the building, access must be provided up to all SOU unit entry doors and to each type of common areas on every level served by the lift or ramp.
This makes sense as generally lifts and ramps are included in mid to large scale developments buildings where there are more SOU units and a greater investment. If continuous access-ways can be provided throughout the building then it’s pretty clear that access can and needs to be provided to more units and common areas.
So, why when a building has a suitable lift, do common stairs still need to be designed to comply with AS1428.1? This question still puzzles some clients and architects and can cause angst in small-scale residential developments where floor space is often limited.
The key reason is for safety. Since the DDA Premises Standards and BCA 2011 came into effect, all common stairs in buildings (excluding fire-isolated stairs) need to comply with AS1428.1. This is regardless of whether or not there is a lift or ramp in the building. By common stairs I mean, stairs not within SOU’s (private stairs) or stairs that lead to areas where access is not required eg. plant room that would be covered by BCA Part D3.4 Exemption.
While it’s clear that stairs don’t form part of the ‘accessible path of travel’ under AS1428.1 and are a barrier for wheelchair users, when they are designed with certain access features stairs can be a safe alternative means of access for people with ambulant disabilities and sensory impairment (vision or hearing).
Stair design needs to satisfy general BCA stair geometry and landing requirements, which include constant riser/ tread dimensions and relationships. To comply with AS1428.1, the following additional features need to be included:
- ‘Opaque’ or closed risers – to stop mobility aids and/or feet slipping/tripping between ‘open’ risers and to minimize disorientation when ascending stairs due to variations in light/glare.
- Stair design/configuration – suitably recessing stair at top and base landings from adjacent paths of travel; and providing off-set tread at base of flights on intermediate landings. This allows the necessary space for safely providing suitable handrail extensions.
- Continuous handrails on both sides – to allow for use by people with limited capability on one side of their body
- Handrail design – suitable profile type/ size, clearances, at a constant height with appropriate extensions to allow for use as a continuous support and guide
- Contrast step nosing – to assist in locating the edge of the step for safety
- TGSI’s – to assist in warning of potential hazards
While architects and designers are generally aware of AS1428.1 stair features, an area that can be easily over-looked is the relationship between stair design/configuration and handrail extensions. In particular, providing an off-set tread at the base of a flight on an intermediate landing as shown on AS1428.1:2009, fig 28.
The critical area is at base of the stair flight on the intermediate landing where the last riser (when descending the stair) needs to be off-set by at least one-tread width. This is needed so that the inner handrail can extend at the same angle (of stair nosings) for the last step (onto the landing) before it turns to continue over the landing (at constant height) to the next stair flight. If no off-set tread is provided it results in a vertical section of handrail which is not permitted under AS1428.1. NB. When the handrail is continuous, the 300mm handrail extension (needed parallel to the landing at the top and base of stairs flights) does not need to be provided for inner handrail on intermediate landing.
People with vision impairment use the handrail extension as a guide to the following ground surface. If no off-set tread is provided at the base of the stair flight (and the slope of the handrail stops in line with last riser) a person with vision impairment could mistakenly think that the following surface is at the same level when actually one more step needs to be taken ie. onto the landing. People with ambulant disabilities also need this extension at the same angle of the stair nosing so that the handrail is at a constant height beside them as support for the last step onto the landing.
Back to the stair and lift issue in residential buildings…. it has been suggested by some, that if a Class 2 building is without a lift eg. 2 - 3 storey walk-up block of flats and provides access to SOU entry doors on the ground floor and each type of common areas also located on the ground floor then a common use stairway to other levels, may not need to be designed to AS1428.1.
For me this is a mistaken interpretation that runs contrary to the reasons why Class 2 buildings were included in the BCA and DDA Access Code in the first place. Presumably these are to improve common area access in residential buildings which will in turn provide more accommodation choices for people with disabilities whether they be visiting, renting or purchasing a SOU unit. If a lift in a residential building is not installed, then surely the stairs within the building should at least be designed with features to assist other people with disabilities safely access other building levels.
This is what is required for small Class 5, 6, 7b or 8 buildings that under the Codes can be exempt from providing lift or ramp access to upper levels (subject to specific criteria). They still must provide entry level access and any common stairs to other building levels must be designed to AS1428.1.
It is interesting to note that BCA 2013 Part D2.17 has extended its requirements for handrails to two new areas. These are fire-isolated stairs/ramps serving areas required to be accessible, that now need to have at least one handrail to comply with AS1428.1 (in terms of profile/ type, size, clearances, installed height) and Class 2, 3 or 4 private SOU’s: that now need to have at least one handrail over all stair/ramp flights with a level change exceeding 1m. The latter requirement is also noted as one of the seven core design features elements for a silver level compliance within the Livable Housing Design Guidelines.
These new BCA inclusions that relate to the general movement of people throughout buildings (and not specifically access for people with disabilities) demonstrate the understanding that suitable handrail provision can improve safe movement on stairways/ramps. Not all buildings need to include a lift, just as not all people (with or without a disability) will choose to use a lift over stairs. However all buildings need to be designed to provide safe access and movement for occupants and it is for this very reason that all buildings with common stairs, including residential buildings without lifts, should have stairs designed to AS1428.1.
Post by Elisa Moechtar