Flashing Cover
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:
- Low, Medium or High Wind Zones, all pitches
- Very High and Extra High Wind Zones where the pitch is equal to or greater than 10°.
Category B:
- Very High where the pitch is less than 8°, and
- Extra High Wind Zones all pitches.
Category C:
- SED Wind Zones up to 60 m/s, all pitches.
Category D:
- SED up to 68 m/s, all pitches.
NOTE: These tables are relevant to trapezoidal profiles with a rib height of 20 – 34 mm and standard corrugate. Longitudinal flashings over profiles with a rib height greater than 34 mm may have one rib overlap
Ridge and Head Flashing Cover Table
|
| Category |
| D |
|---|---|---|---|---|
| C1 | 130 mm | 200 mm | 200 mm | 200 mm + baffle |
| Ridge Type | Standard | Wide | Wide | |
| Purlin Position X | ||||
| Pitch 8°–15° | 165 mm | 150 mm | 150 mm | 150 mm |
| Pitch 15°–30° | 150 mm | 200 mm | 200 mm | 200 mm |
| Pitch 30°–45° | 130 mm | 180 mm | 180 mm | 180 mm |
Barge Flashing Cover — Trapezoidal and Secret Fixed Table
|
| Category |
|
|
|---|---|---|---|---|
| C2 | 1 rib | 2 ribs | 2 ribs | 2 + undersoaker |
| C1 (smooth surface) | 50 mm | 75 mm | 75 mm | 75 mm |
| C1 (profiled surface) | 75 mm | 100 mm | 125 mm | 125 mm |
Barge Flashing Cover — Corrugate Table
|
| Category |
|
|
|---|---|---|---|---|
| C2 | 2 crests | 2 crests | 3 crests | 2 + undersoaker |
| C1 (smooth) | 50 mm | 75 mm | 75 mm | 75 mm |
| C1 (profiled) | 75 mm | 100 mm | 125 mm | 125 mm |
Transverse Apron Flashing Cover Table
|
| Category |
|
|
|---|---|---|---|---|
| C1 (smooth surface) | 50 mm + hem or 75 mm | 75 mm + hem or 100 mm | 100 mm + hem or 125 mm | 100 mm + |
| C1 (profiled surface) | 75 mm + hem or 100 mm | 100 mm + hem or 125 mm | 125 mm | 125 mm |
| C2 | 130 mm | 200 mm | 200 mm + baffle | 200 mm + baffle |
Apron Flashing Cover – Trapezoidal Table
|
| Category |
|
|
|---|---|---|---|---|
| C2 | 1 rib | 2 ribs* | 2 ribs | 2 ribs + undersoaker |
| C1 (smooth surface) | 50 mm + hem or 75 mm | 75 mm + hem or 100 mm | 100 mm + hem or 125 mm | 100 mm + |
| C1 (profiled surface) | 75 mm + hem or 100 mm | 100 mm + hem or 125 mm | 125 mm | 125 mm |
Apron Flashing Cover – Corrugate Table
|
| Category |
|
|
|---|---|---|---|---|
| C2 | 2 crests | 2 crests | 3 crests | 2 + undersoaker |
| C1 (smooth surface) | 50 mm + hem or 75 mm | 75 mm + hem or 100 mm | 100 mm + hem or 125 mm | 100 mm + hem or 125 mm |
| C1 (profiled surface) | 75 mm + | 100 mm + hem or 125 mm | 125 mm + hem | 125 mm |
Parapet Cap Cover Table
|
| Category |
|
|
|---|---|---|---|---|
| C1 (smooth surface) | 50 mm | 75 mm | 75 mm | 75 mm |
| C1 (profiled surface) | 75 mm | 100 mm | 125 mm | 125 mm |
Change of Pitch Flashing Cover Table
|
| Category |
|
|
|---|---|---|---|---|
| C1 | 250 mm | 250 mm | 300 mm | 300 mm |
| C2 | 150 mm | 200 mm | 200 mm | 200 mm + baffle |
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