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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.

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

 

Barge Flashing Cover — Trapezoidal and Secret Fixed Table


Dimension


A

Category
B


C


D

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

 

Barge Flashing Cover — Corrugate Table


Dimension


A

Category
B


C


D

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

 

 

Transverse Apron Flashing Cover Table


Dimension


 A

Category
B


C


D

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 +
hem or
100 mm
100 mm +
hem or
125 mm
125 mm125 mm
C2130 mm200 mm200 mm
+ baffle
200 mm +
baffle
 

 

 

Apron Flashing Cover – Trapezoidal Table


Dimension


A

Category
B


 C


D

C21 rib2 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 +
hem or
125 mm

C1 (profiled
surface)
75 mm +
hem or
100 mm
100 mm +
hem or
125 mm
125 mm125 mm
*Not to exceed 300 mm. Two ribs cover can consist of two machined crests or one machined crest plus an upstand, hand-formed from the adjacent pan.

 

 

Apron Flashing Cover – Corrugate Table


Dimension


A

Category
B


C


D

C22 crests2 crests3 crests2 +
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 +
hem or
100 mm

100 mm +
hem or
125 mm
125 mm +
hem
125 mm
 

 

Parapet Cap Cover Table


Dimension


A

Category
B


C


D

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

 

Change of Pitch Flashing Cover Table


Dimension


A

Category
B


C


D

C1250 mm250 mm300 mm300 mm
C2150 mm200 mm200 mm200 mm +
baffle
 
Clause: 
008_004_000_000_000_000_000_000_000
Clause Number: 
8.4
/cop/flashings/flashing-cover
Revision Category: 
1 - Minor Errata
Revision Detail: 

Fixed typo. changed "m" to "mm".