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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.

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 

 


Dimension


A

Category
B


C

C1130 mm200 mm200 mm
+ baffle
Ridge TypeStandardWideWide
    
Purlin Position X   
Pitch 8°–15°165 mm150 mm150 mm
Pitch 15°–30°150 mm200 mm200 mm
Pitch 30°–45°130 mm180 mm180 mm
 

 

 


Dimension


A

Category
B


C

C21 rib2 ribs2 ribs
C1  (smooth
surface)
50 mm75 mm75 mm
C1  (profiled
surface)
75 mm100 mm125 mm
 

 

 


Dimension


A

Category
B


C

C22 crests2 crests3 crests
C1 (smooth)50 mm75 mm75 mm
C1 (profiled)75 mm100 mm125 mm
 

 

 

 


Dimension


 A

Category
B


C

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
C2130 mm200 mm200 mm
+ baffle
 

 

 

 


Dimension


A

Category
B


 C

C21 rib2 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
 

 

 

 


Dimension


A

Category
B


C

C22 crests2 crests3 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 +
hem or
100 mm

100 mm +
hem or
125 mm
125 mm +
hem
 

 

 


Dimension


A

Category
B


C

C1 (smooth
surface)
50 mm75 mm75 mm
C1 (profiled
surface)
75 mm100 mm125 mm
 

 

 


Dimension


A

Category
B


C

C1
250 mm250 mm300 mm
C2150 mm200 mm200 mm
 
/cop/flashings/flashing-cover
Revision Category: 
3 - Substantial change to recommendation
Revision Detail: 

Increased recommended cover for Barge Flashing Cover — Trapezoidal and Secret Fixed and Barge Flashing Cover — Corrugate Category C from 50 mm to 75 mm.