AS 4654.2 stipulates the requirement for upward vertical termination height of an external waterproofing membrane. The height requirement ranges from 40 mm to 180 mm depending on the building’s wind class. Note that this is the height required above finished floor level.
Wind Class Regions A & B (non-cyclonic) AS 4055 | Wind class Regions C & D (cyclonic) AS 4055 | Ultimate limit state (V_{h,u}) AS/NZS 1170.2 | Termination Height (mm) |
N1 | - | 34 | 40 |
N2 | - | 40 | 50 |
N3 | C1 | 50 | 70 |
N4 | C2 | 61 | 100 |
N5 | C3 | 74 | 150 |
N6 | C4 | 86 | 180 |
Remember the quoted termination height is the height above finished floor level.
A building’s wind classification (AS 4055) can be calculated in accordance with AS 1170.2 which sets out 4 primary factors for determining a building’s wind class determination:
- Geographic wind speed region
- Terrain category
- Topography
- Shielding
A guide to calculating wind class can be found here. Calculations should be undertaken by an engineer familiar with AS 1170.2.
If you are going to have falls in your finished floor, then you will need to work out the required falls and calculate the finished floor levels prior to working out where your membrane will terminate.