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 four 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 10°, 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
| Dimension | A | Category B | C | D | ||||
|---|---|---|---|---|---|---|---|---|
| C1 | 130 | 200 | 200 | 200 | ||||
| Ridge Type | Standard | Wide | Wide | |||||
| First Purlin Position X | ||||||||
| Pitch | 8° | 10° | 15° | 20° | 25° | 30° | 35° | 45° |
| 168 | 167 | 162 | 156 | 150 | 143 | 134 | 115 | |
Barge Flashing Cover — Trapezoidal and Secret Fixed Table
|
| Category |
|
|
|---|---|---|---|---|
| C2 | 1 upstand | 2 upstands | 2 upstands | 2 + undersoaker |
| C1 (smooth surface) | 50 | 75 | 75 | 75 |
| C1 (profiled surface) | 75 | 100 | 125 | 125 |
Barge Flashing Cover — Corrugate Table
|
| Category |
|
|
|---|---|---|---|---|
| C2 | 2 upstands | 2 upstands | 3 upstands | 2 + undersoaker |
| C1 (smooth) | 50 | 75 | 75 | 75 |
| C1 (profiled) | 75 | 100 | 125 | 125 |
Transverse Apron Flashing Cover Table
|
| Category |
|
|
|---|---|---|---|---|
| C1 (smooth surface) | 50 + hem or 75 | 75 + hem or 100 | 100+ hem or 125 | 100+ |
| C1 (profiled surface) | 75 + hem or 100 | 100 + hem or 125 | 125 | 125 |
| C2 | 130 | 200 | 200 + baffle | 200 + baffle |
Apron Flashing Cover – Trapezoidal Table
|
| Category |
|
|
|---|---|---|---|---|
| C2 | 1 upstand | 2 upstands* | 2upstands | 2 upstands + undersoaker |
| C1 (smooth surface) | 50 + hem or 75 | 75 + hem or 100 | 100 + hem or 125 | 100+ |
| C1 (profiled surface) | 75 + hem or 100 | 100 + hem or 125 | 125 | 125 |
Apron Flashing Cover – Corrugate Table
|
| Category |
|
|
|---|---|---|---|---|
| C2 | 2 upstands | 2 upstands | 3 upstands | 2 upstands + undersoaker |
| C1 (smooth surface) | 50+ hem or 75 | 75 + hem or 100 | 100 + hem or 125 | 100 + hem or 125 |
| C1 (profiled surface) | 75 + | 100 + hem or 125 | 125 + hem | 125 |
Parapet Cap Cover Table
|
| Category |
|
|
|---|---|---|---|---|
| C1 (smooth surface) | 50 | 75 | 75 | 75 |
| C1 (profiled surface) | 75 | 100 | 125 | 125 |
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