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When the Performance-Based Building Code was introduced in 1996, WA was the first State to adopt it. The new Code provided the flexibility that was lacking in the Uniform Building By-Laws that prescribed the minimum requirements for compliance of residential and non-residential buildings.

The performance-based Building Code of Australia (BCA) maintains the prescriptive requirements as Deemed-to-Satisfy (DTS) Clauses as one way to demonstrate compliance. Most buildings follow the DTS for most of the design aspects for compliance. It is a tried and tested way of complying with the construction, fire, access for people with disabilities, health and amenity, and energy efficiency requirements of the BCA.

Not all building design requirements and sites can adhere to the prescriptive requirements of the DTS Clauses. This is where the Performance Criteria of the BCA enable a proponent to include a Building Solution for the development that addresses the Performance Criteria to demonstrate compliance with a Section or Part of the BCA instead of using the DTS. The BCA enables compliance through the DTS, the Performance Provisions, through a Building Solution, or a combination of both.

It should be kept in mind that Alternative Solutions are used to address site or design constraints for a building proposed i.e. Alternative Solutions should be part of a design solution. Alternative Solutions should not be proposed post-construction as a way to fix a construction problem once an error has been identified.


An alternative solution must be documented to address the requirements of the BCA and written by a suitably qualified person. A Building Surveyor assesses the proposed Alternative Solution against the relevant Performance Criteria and be satisfied the person documenting the Alternative Solution is suitably qualified, to show the building is compliant with the relevant Performance Clauses. It is important to note that proposing an Alternative solution for one section of the BCA, may impact the compliance of the building with another section of the BCA. All of these must be considered to ensure overall building compliance with relevant building standards.


An upper level addition is proposed to an existing building. The building has limited space for the installation of a stair to the upper level. In order to meet the DTS requirements of the BCA, the designer would need to follow the prescriptive requirements of the Clauses and Tables of the BCA for Stair construction. In this case a suitable landing would be required as the number of risers of the stairway exceeds the maximum 18 allowable under the DTS provisions. By including the landing, the stairway is separated into two flights containing less than 18 risers. The only way for the stairway to provide access to the upper level is to have 19 continuous risers with slightly shorter treads and slightly higher risers than the BCA allows in Table 3.9.1.

The Building Surveyor must be satisfied that the performance requirement of the BCA are addressed, and design and subsequent construction is compliant. A suitably qualified person to provide an Alternative Solution to address this issue is a Building Surveyor. The Building Surveyor would document a report that demonstrates the proposed design adequately addresses the performance criteria for safe movement and access. If the Building Surveyor can show the design meets this criteria, the design is compliant with the BCA.

This process is not always understood. In a situation like this, solutions are not worked on at design stage. Instead, the drawings are made to appear compliant and/or conditioned for compliance with the BCA with notations on plans i.e. stairway to meet BCA requirements, and then the builder is left to solve the issues on site when the stairway doesn’t work, or cannot be constructed to achieve compliance.

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