COP v3.0:flashings; flashing-cover

8.3 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 

8.3D  


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
 

 

8.3F  


Dimension


A

Category
B


C

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

 

8.3H  


Dimension


A

Category
B


C

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

 

 

8.3J  


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
 

 

 

8.3L  


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
 

 

 

8.3N  


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
 

 

8.3P  


Dimension


A

Category
B


C

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

 

8.3R  


Dimension


A

Category
B


C

C1
250 mm250 mm300 mm
C2150 mm200 mm200 mm
 

8.3.1 Apron Upstands 

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.

8.3.2 Clearances 

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.

8.3.3 Ridging and Other Transverse Flashings 

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.

8.3.4 Flashing Laps 

Laps in flashings should comply with the following criteria:

  • Water must flow over a lap, not into it,
  • a lap must not rely solely on sealant,
  • sealed laps must be mechanically fixed at 50 mm centres, and
  • end laps must be a minimum of 150 mm for unsealed laps and 100 mm for sealed laps.