Code of Practice v3.0 Online
The NZ Metal Roof and Wall Cladding Code of Practice is a comprehensive design & installation guide, and a recognised related document for Acceptable Solution E2/AS1 of the NZ Building Code.
The NZ Metal Roof and Wall Cladding Code of Practice is a comprehensive design & installation guide, and a recognised related document for Acceptable Solution E2/AS1 of the NZ Building Code.
The weathertightness of a flashing is determined by the flashing cover (C), not the flashing dimension.(D) Other considerations are catchment area, wind exposure, roof pitch and profile height.
The minimum flashing cover (C) must correlate with the tables below.
There are three categories of exposure or pitch that determine the required flashing cover .
Category A:
Category B:
Category C:
NOTE: These tables are relevant to trapezoidal profiles with a rib height of 25 – 34 mm and standard corrugate. Longitudinal Apron flashings over profiles with a rib height greater than 34 mm may have one rib overlap
|
| Category |
|
---|---|---|---|
C1 | 130 mm | 200 mm | 200 mm + baffle |
Ridge Type | Standard | Wide | Wide |
Purlin Position X | |||
Pitch 8°–15° | 165 mm | 150 mm | 150 mm |
Pitch 15°–30° | 150 mm | 200 mm | 200 mm |
Pitch 30°–45° | 130 mm | 180 mm | 180 mm |
|
| Category |
|
---|---|---|---|
C2 | 1 rib | 2 ribs | 2 ribs |
C1 (smooth surface) | 50 mm | 75 mm | 75 mm |
C1 (profiled surface) | 75 mm | 100 mm | 125 mm |
|
| Category |
|
---|---|---|---|
C2 | 2 crests | 2 crests | 3 crests |
C1 (smooth) | 50 mm | 75 mm | 75 mm |
C1 (profiled) | 75 mm | 100 mm | 125 mm |
|
| Category |
|
---|---|---|---|
C1 (smooth surface) | 50 mm + hem or 75 mm | 75 mm + hem or 100 mm | 100 mm + hem or 125 mm |
C1 (profiled surface) | 75 mm + hem or 100 mm | 100 mm + hem or 125 mm | 125 mm |
C2 | 130 mm | 200 mm | 200 mm + baffle |
|
| Category |
|
---|---|---|---|
C2 | 1 rib | 2 ribs* | 2 ribs |
C1 (smooth surface) | 50 mm + hem or 75 mm | 75 mm + hem or 100 mm | 100 mm + hem or 125 mm |
C1 (profiled surface) | 75 mm + hem or 100 mm | 100 mm + hem or 125 mm | 125 mm |
|
| Category |
|
---|---|---|---|
C2 | 2 crests | 2 crests | 3 crests |
C1 (smooth surface) | 50 mm + hem or 75 mm | 75 mm + hem or 100 mm | 100 mm + hem or 125 mm |
C1 (profiled surface) | 75 mm + | 100 mm + hem or 125 mm | 125 mm + hem |
The minimum cover of the updated of an apron flashing varies depending on whether the upstand is hemmed or unhemmed, and the covering cladding is smooth or profiled. Profiled claddings require more coverage because they allow vertical air movement through the voids of the profile.
The end of wall cladding should have a minimum clearance of 25 mm from an apron flashing or another horizontal surface. Where vegetation is present, or debris may accumulate, greater clearances or regular maintenance is required to achieve optimum durability. See 4 Durability.
A soft edge or notched flashing must be provided to transverse flashings. The positioning of the top purlin must be adjusted with the pitch and the ridge girth to ensure that primary fastening is provided between 15 mm and 50 mm from the leading edge of the flashing. See 8.3C Ridge and Head Flashing Cover.
Laps in flashings should comply with the following criteria: