Ensuring Compliance with AS 1428.1 and BCA: Limiting Riser Openings to 125 mm in Commercial Staircases

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When performing detailed engineering for commercial staircases and balustrades, it’s essential to ensure that all aspects comply with AS 1428.1 and the relevant provisions from the Building Code of Australia (BCA), particularly those regarding accessibility and safety. Here’s a breakdown of the critical points you must address:

Compliance with AS 1428.1:
1. This standard outlines the minimum technical requirements for accessible buildings. Engineers must reference the BCA to align with safety and access provisions. AS 1428.1 directs engineers to follow BCA for detailed requirements related to stair and balustrade design, ensuring all safety standards are met, particularly for disabled access.

2. BCA 3.9.1.3 – Riser Opening Requirement:
One of the key safety provisions under BCA 3.9.1.3 is ensuring that the riser openings on stairways are restricted. Specifically, the gap between treads must not allow a 125 mm sphere to pass through. This rule is vital for preventing accidents, such as children slipping through open risers. As a detailed engineer, you must ensure that this riser opening specification is incorporated into the technical drawings and calculations to meet safety compliance.

3. BCA 3.9.1.4 – Riser and Going Dimensions:
Further, BCA 3.9.1.4 provides specific dimensional requirements for stair risers and goings, as illustrated in Figure 3.9.1.2. This figure shows the maximum and minimum values for risers (R) and goings (G), as well as the slope relationship (2R + G). Engineers must adhere to these dimensions for both spiral and non-spiral staircases to ensure that the stairs are not only safe but also ergonomically comfortable for users.

4. Critical Figures:

Riser (R): Must be within the maximum and minimum values—115 mm to 190 mm for standard stairs and 140 mm to 220 mm for spiral stairs.

Going (G): Must be within the maximum and minimum values—240 mm to 355 mm for standard stairs and 210 mm to 370 mm for spiral stairs.

Slope Relationship (2R + G): Must fall between 550 mm and 700 mm for standard stairs and 590 mm to 680 mm for spiral stairs. These values ensure that stairs provide both safety and comfort.

5. Ensuring Compliance:
As part of the detailed engineering process, it’s your responsibility to ensure that all specifications, such as the 125 mm riser opening limit and the exact riser and going dimensions, are strictly followed in the drawings, materials, and construction processes. This involves validating these measurements on-site and ensuring they are reflected accurately in both the design and construction stages.

In conclusion, the detailed engineering process must ensure compliance with AS 1428.1 and the BCA, particularly regarding the requirement that the riser opening must not exceed 125 mm, as outlined in BCA 3.9.1.3. Additionally, the riser and going dimensions must conform to the standards specified in BCA 3.9.1.4. By adhering to these standards, you will ensure that commercial stairs and balustrades are safe, accessible, and compliant with Australian building regulations.


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