Duty class (wall ties)
A duty class (light, medium, heavy) grades the load a wall tie can transfer under AS 2699.1, matched to wind classification through the NCC Housing Provisions.
Ask Chalkline about this →A duty class is the strength grading, light, medium, or heavy duty, given to a wall tie or masonry connector under AS 2699.1, based on the load it can transfer between the leaves of a wall. It is how a tie’s structural capacity is specified: a light-duty tie carries less load than a medium-duty one, and the wall’s wind exposure decides which you need.
The duty class is matched to the wind classification and the wall type through the NCC 2022 Housing Provisions (Table 5.6.5):
| Duty class | Typical use |
|---|---|
| Light duty | Masonry veneer at wind class N2 or below; cavity masonry at N1 |
| Medium duty | Veneer above N2, cavity masonry above N1, solid masonry, non-engaged piers |
| Heavy duty | Engineered masonry, tall parapets, post-frame, per engineering design |
So a higher wind class, or a topographic or terrain reason the class steps up, pushes you to a higher-duty tie.
Duty class is not the same as corrosion class. Duty class is about strength (the load); the corrosion class (R1 to R4) is about durability, how well the tie resists corrosion in its environment. A coastal cavity wall might need a medium-duty tie for the wind and a 316 stainless (high corrosion class) tie for the salt, both at once. Select both off the wall tie tables, embed the tie at least 50 mm into each leaf, and do not downgrade either to save a few cents. See wall ties and AS 2699.
Also known as: Tie duty class, wall-tie duty rating.
Category: Masonry / Wall ties.
Related
See also
References
- AS 2699.1:2020 Built-in components for masonry construction, Wall ties, Standards Australia (verified 2026-05-11)
- ABCB NCC 2022 Housing Provisions Part 5.6 (masonry) (verified 2026-05-11)
Last updated: 2026-05-30. Verified: 2026-05-11. Quarterly review for currency.