Wind classification guide
N and C wind classifications: what the rating means
The AS4055 classification ranges are N1 through N6 for non-cyclonic sites and C1 through C4 for cyclonic sites. A project's classification describes the wind classification for its nominated site and helps builders, designers and suppliers coordinate suitable building products and structural details.
By Dominic (Son Hai) Nguyen, Senior Structural Engineer · Last reviewed
NER 4070460 · NSW Design Practitioner DEP0003685 · RPEQ 23510
Direct answer
If a supplier or certifier asks for an N or C wind rating, they are usually asking for the AS4055 site wind classification. QuickWind provides that standalone certificate for suitable projects. If you are ordering complete structural documentation for a suitable Class 10 building, QuickFrame10 considers the applicable wind basis within the design.
What N and C indicate
In broad terms, N classifications are commonly associated with non-cyclonic wind classifications and C classifications with cyclonic wind classifications. The full ranges run from N1 to N6 and C1 to C4. The exact classification depends on the nominated site and applicable assessment pathway.
Why the number matters
The number attached to the classification affects what wind-rated products or design details may be needed. Suppliers and project designers use the classification to coordinate items such as windows, doors, garage doors, roof trusses, cladding and tie-down requirements.
How the certificate fits into structural design
A site wind classification certificate identifies the wind classification for the nominated site. Members, connections, bracing, tie-down and footings are then resolved through the structural design, while suppliers retain responsibility for products within their scope.
Which product should I choose?
- QuickFrame10: complete structural documentation for a suitable Class 10 building with its own structural system and load path to the ground.
- QuickWind: a standalone AS4055 site wind classification certificate for a suitable Class 1 or Class 10a project.