What standards apply to your project?

Currently the two standards that apply are:

• AS 4055:2012 (most commonly applied to residential housing — gives a wind rating)
• AS/NZS 1170.2:2011 (used when the geometric limits of AS 4055 are exceeded, e.g. roof height over 8.5m — gives a design wind speed).

Further, the following contributing factors are considered to formulate results to determine what is required with your particular project:

• Wind Region — based on updated standards available for different regions of Australia (see region map below)
• Shielding — what is considered as ‘shielding’ of the structure by adjacent structures and trees (AS 4055 only)
• Terrain — consideration to smoothness or roughness of the terrain due to trees and other structures. For AS 4055 this includes considering terrain within 500 metres in all directions. AS/NZS 1170.2 includes an averaging distance of 500 metres or 40 times average of the project roof height plus a lag distance, whichever is greater.  
• Topography — considers any significant cross sections of a hill, any site where it is located on a hill and site slope.

What changes have been made to wind assessment standards?

The new standards will be aligned more closely to each other. Some key changes which may impact the ratings for your projects are as follows: 

AS 4055:2021 (Wind loads for housing)

1. The geometric limitations of AS 4055 have been clarified with the introduction of the term “averaged ground level”, defined as the natural ground level excluding earthworks where earthworks are minor, or through the modified land where the earthworks are major. This may lead to more projects sitting outside the limitations of AS 4055 and therefore coming under AS/NZS 1170.2:2021.  
2. Terrain Category 1.5 has been removed. Bodies that fit into this category are now in TC1.
3. Some wind region zoning has changed. Most notably for South East Queensland, Toowoomba is now in Region B, not Region A.
4. Calculation of topographic class was previously taken as the maximum slope through the closest peak. It now explicitly states that the slope must run through the project site.  This brings AS 4055 more in line with AS/NZS 1170.2 and better takes into account conditions at the project site.
5. A subsequent revised wind classification table (refer below)
6. Equivalent wind ratings from AS/NZS 1170.2 are now allowed for the purpose of specifying building products (eg windows, doors and cladding).

AS/NZS 1170.2:2021  (Structural design actions, Part 2: Wind actions)

1. For wind regions B2, C & D, a newly introduced climate change multiplier (Mc) will account for possible changes in climate affecting extreme winds over the design life of buildings. This may be adjusted in future, depending on observed or predicted trends.
2. The wind regions map has changed and regions A0, B1 (including Toowoomba) and B2 have been introduced (see updated map below)  
3. Wind direction multipliers have been revised for all wind regions in Australia.
4. Terrain category TC1.5 has been removed (as per AS 4055) and multipliers for TC1 have been slightly reduced.

Design Wind Speed Calculations According to AS1170.2:2021 (Updated Code)

Based on structure lifespan 25 years / Max av. height 10m		Terrain Category 2 for all calculations
AUSTRALIAN WIND REGION	ULTIMATE REGIONAL WIND SPEED (km/h)	IMPORTANCE LEVEL	DESIGN WIND SPEED (km/h)
Region A0	162	1	148
		2	154
		3	162
Region A1 to A5	162	1	148
		2	154
		3	162
Region B1	205	1	164
		2	177
		3	194
Region B2	205	1	163
		2	176
		3	192
Region C	238	1	192
		2	207
		3	255
Region D	288	1	226
		2	246
		3	271

Will the changes affect project cost?

There are likely to be variations in results from the old to new standards, some more favourable (costing less for the build), and others not so. The goal of the changes is to improve the system, making wind assessments more accurate (with AS 4055 becoming more consistent with AS/NZS 1170) and therefore safer and more enduring structures. 

In short, the requirements and costs related to your project will be determined once your location, wind region, terrain category and importance level are determined.

How Techspan Can Help

When you begin the design consultation at Techspan, location is one of the early questions we ask. We consider your location with respect to Wind Region, Terrain Category and Importance Level and factor this into the design and engineering stages to ensure that your project meets the required standard, in accordance with AS/NZS 1170.2.

In some cases, local councils may also have specific requirements that will also be taken into consideration. 

It is extremely important to classify every structure on a case-by-case basis and assess every location individually. If wind is not properly discussed or considered in the design process it could be hazardous and affect the longevity of your structure. 

Safety and Structural Integrity are key considerations within our design philosophy here at Techspan and ensuring that all Techspan projects are ‘structured to work’ for many years to come. 

With over 20 years’ experience in the industry and hundreds of aviation, rural, agribusiness, mining, commercial, industrial and school infrastructure projects delivered, our team are here to make the process of achieving your new project simple.

What is the PCA and what is their role?

The main roles of the Principal Certifying Authority (PCA) include:

• Ensure compliance with the development consent and the construction certificate or the complying development certificate;
• Ensure compliance with all the relevant development conditions;
• Ensure compliance with the Building Code of Australia;
• Carry out all the required inspections associated with the building works;
• Issue the occupation certificate when all works are completed.

What is a Town Planner?

A town planner works on behalf of the developer or landowner and can advise on and assess your development idea and plans. Town planners can develop a strategy and help put together reports to ensure the best outcome in the council approval process.

What is an Architectural Draftsman?

An architectural draftsman will turn the architectural concepts into drawings and plans that can be submitted as part of your approvals process.

What is a Structural Engineer?

A structural engineer’s job is to ensure that your building design is structurally sound. They will analyse the properties of your structure, test the behaviour and durability of materials used in their construction, and design and supervise the construction of all types of buildings to ensure they will stand up to the conditions and use they’re intended for.

What is a Civil Engineer?

Civil engineers design and plan the construction of dams, bridges, pipelines, sewage systems, roads and other civil projects. They also analyse the likely behaviour of soil and rock at the site of your proposed development to ensure your new building and its foundations will be structurally sound.

What is the Role of A Builder?

A builder oversees and coordinates the construction of your new building, and can manage the entire project. The builder is responsible for managing schedules, organising other trades, managing quality and compliance, managing the site, and ensuring WHS rules are enforced. There are strict safety regulations including wearing protective equipment, and ensuring the site is safe for other necessary site visitors that builders must comply with.

What is a Private Certifier?

Registered certifiers assess and determine applications for development certificates for building and subdivision work. Most certifiers are qualified building surveyors who can issue development certificates for building work, be appointed as the principal certifier, and carry out inspections.

What is TechSpan’s Role?

TechSpan does not take on the role of the builder or principal contractor. TechSpan is responsible for the design, structural engineering, and the supply and installation of the structural steel and cladding package. Our scope includes all structural steel, cladding, doors, windows and rainwater goods to ground level. Techspan can also help with civil and concrete engineering design, and connect you with our ever-growing network of SmartPoint verified consultants and tradespeople to support you with installation, as needed.

Building Classes Overview

Class 1.

Class 1a – A single dwelling being a detached house, or one or more attached dwellings, each being a building, separated by a fire-resisting wall, including a row house, terrace house, townhouse or villa unit.

Class 1b – A boarding house, guest house, a hostel or the like with a total area of all floors not exceeding 300m2, and where not more than 12 reside and is not located above or below another dwelling or another Class of building other than a private garage

Class 2.

A building containing 2 or more sole-occupancy units each being a separate dwelling.

Class 3.

A residential building, other than a Class 1 or 2 building, is a commonplace of long term or transient living for a number of unrelated persons. Example: boarding-house, hostel, backpackers accommodation or residential part of a hotel, motel, school or detention centre.

Class 4.

A dwelling in a building that is Class 5, 6, 7, 8 or 9 if it is the only dwelling in the building.

Class 5.

An office building that is used for professional or commercial purposes, excluding buildings of Class 6, 7, 8 or 9.

Class 6.

A shop or other building for the sale of goods by retail or the supply of services direct to the public. Example: café, restaurant, kiosk, hairdressers, showroom or service station.

Class 7.

Class 7a – A building which is a car park.

Class 7b – A building which is for storage or display of goods or produce for sale by wholesale.

Class 8.

A laboratory or a building in which a handicraft or process for the production, assembling, altering, repairing, packing, finishing or cleaning of goods or produce is carried on for trade, sale or gain.

Class 9.

A building of a public nature.

Class 9a – A health care building, including those parts of the building set aside as a laboratory.

Class 9b – An assembly building, including a trade workshop, laboratory, or the like, in a primary or secondary school, but excluding any other parts of the building that are of another class.

Class 9c – An aged care building.

Class 10.

A non-habitable building or structure.

Class 10a – A private garage, carport, shed or the like.

What Building Class is My New TechSpan Building?

Class 7b — Storage Buildings

A building which is for storage or display of goods or produce for sale by wholesale.

Examples of TechSpan buildings that would fall into this category are showrooms and warehouses.

Class 8 — Processing & Factory Buildings

A laboratory or a building in which a handicraft or process for the production, assembling, altering, repairing, packing, finishing or cleaning of goods or produce is carried on for trade, sale or gain.

Examples of TechSpan buildings that would fall into this category are factory, packing, product, manufacturing and workshop sheds.

Class 9b — Assembly Buildings

An assembly building, including a trade workshop, laboratory, or the like, in a primary or secondary school, but excluding any other parts of the building that are of another class.

An example of TechSpan buildings that would fall into this category is school COLAs.

Class 10a — Carports & Sheds

A private garage, carport, shed or the like.

Examples of TechSpan buildings that would fall into this category are multipurpose farm sheds and private machinery sheds.

Building Classes

There are ten building classes set out in the Building Code of Australia that each structure is categorised into. TechSpan buildings typically fall into one of the four classes outlined below.

To see the full list of all building classes, check out our building classes overview.

Class 7b — Storage Buildings

A building which is for storage or display of goods or produce for sale by wholesale.

Examples of TechSpan buildings that would fall into this category are showrooms and warehouses.

Class 8 — Processing & Factory Buildings

A laboratory or a building in which a handicraft or process for the production, assembling, altering, repairing, packing, finishing or cleaning of goods or produce is carried on for trade, sale or gain.

Examples of TechSpan buildings that would fall into this category are factory, packing, product, manufacturing and workshop sheds.

Class 9b — Assembly Buildings

An assembly building, including a trade workshop, laboratory, or the like, in a primary or secondary school, but excluding any other parts of the building that are of another class.

An example of TechSpan buildings that would fall into this category is school COLAs.

Class 10a — Carports & Sheds

A private garage, carport, shed or the like.

Examples of TechSpan buildings that would fall into this category are multipurpose farm sheds and private machinery sheds.