What you need to know about the new wind assessment standards

In September 2022, the National Construction Code (NCC) was updated with changes to the Wind Assessment Standards. At Central Steel Build, we are committed to ensuring our projects not only comply with these new standards but also deliver high-quality, efficient, and durable structures that boost productivity, safety, security, and accessibility, specifically designed to your needs. From initial consultation through to design, engineering, material selection, and manufacturing, our dedication to customer satisfaction and attention to detail distinguishes us in the industry.

Which standards are relevant to your project? 

Currently, two key standards are relevant:

• AS 4055:2012 – Typically used for residential buildings to determine wind ratings.
• AS/NZS 1170.2:2011 – Applied when projects exceed the geometric limits of AS 4055, typical for most Central Steel Build projects.

Several factors are considered to determine the specific requirements for your project:

• Wind Region – Assessed based on the latest regional standards across Australia.
• Shielding – The level of shielding provided by nearby structures.
• Terrain – The terrain's smoothness or roughness is considered within a 500-metre radius for AS 4055, or with an averaging distance in AS/NZS 1170.2.
• Topography – Evaluates the site’s location on a hill and the slope's impact on wind assessment.

What are the key changes to wind assessment standards? 

The new standards now align more closely. Notable changes that may affect your project include:

• AS 4055:2021 (Wind loads for housing)
  • The concept of "averaged ground level" has been introduced, potentially shifting more projects under AS/NZS 1170.2:2021.
  • Removal of Terrain Category 1.5, merging it with TC1.
  • Changes in wind region zoning, such as Toowoomba moving to Region B.
  • Clarification that topographic class calculations must consider the slope directly through the project site.
  • Introduction of an updated wind classification table.
  • Allowing equivalent wind ratings from AS/NZS 1170.2 for building product specifications.
    
    
• AS/NZS 1170.2:2021 (Structural design actions, Part 2: Wind actions)
  • Introduction of a climate change multiplier for wind regions B2, C, and D, considering potential future climate impacts on wind conditions.
  • Revisions to the wind regions map and the introduction of regions A0, B1, and B2.
  • Adjustments to wind direction multipliers across all wind regions.
  • Terrain category TC1.5 has been removed, with slight reductions in multipliers for TC1.
  • Additional dominant opening factor of 8.5% for buildings with open side walls.
  • Terrain category 2 is always applied for wind region A0.

Designed wind speed calculations according to AS1170.2:2021 

How will these changes impact on project costs? 

The shift from the old to the new standards may result in cost variations, with most projects seeing an increase. The purpose of these changes is to enhance the accuracy of wind assessments, leading to safer and more resilient structures.

Ultimately, the specific requirements and associated costs for your project will depend on factors such as location, wind region, terrain category, and importance level.

How Central Steel Build can support your project 

At Central Steel Build, we take your location into account early in the design process, evaluating factors such as Wind Region, Terrain Category, and Importance Level to ensure your project adheres to AS/NZS 1170.2. In some instances, local council requirements will also be integrated into our design considerations.

It’s crucial to evaluate each structure on a case-by-case basis and thoroughly assess the site’s specific conditions. Proper consideration of wind factors during the design phase is essential for ensuring safety and the longevity of your structure.

Structural integrity is at the core of our design philosophy at Central Steel Build, and we are committed to delivering structures that stand the test of time.

With over four decades of experience and a portfolio of successful projects across various sectors, including, rural, agribusiness, commercial, industrial, equestrian, aviation, and educational infrastructure, our team is here to simplify the process of bringing your project to life. 

If you're interested in learning how our custom-design solutions can benefit you and your structure, contact our project consultants for a detailed discussion and request an obligation-free quote.