COP v3.0:flashings; flashing-materials

8.1 Flashing Materials 

Exposed flashings are typically manufactured using the same base metal material as used for the roof and wall cladding. If flashings are required to match the colour of the profiled cladding, it is necessary for the pre-painted flat sheet or coil to be made by the same manufacturer, using the same process. When it is not possible, or if different materials are intended or specified, the alternative materials should be compatible considering both contact and runoff. (See 4.9.4 Compatibility Table)

All flashings must be fabricated from a ductile material and designed for lateral strength by folding, stiffening, or ribbing on external edges, with a maximum unstiffened width of 300 mm.

Vertical faces of flashings such as barges and fascia can exhibit oil canning. This can be minimised by using heavier gauge material, by forming stiffeners, or by providing clip fastened attachment systems which allow for thermal movement. In critical visual areas, the COP recommends a maximum unstiffened depth of 200 mm on the vertical face.

Metal flashings must have a bend radius complying with the minimum radii prescribed in 4.10.8 Microcracking.
The minimum thickness for metal flashings must be:
  • Coated steel — 0.55 mm,
  • Aluminium — 0.70 mm,
  • Copper — 0.60 mm,
  • Zinc — 0.70 mm,
  • Stainless steel — 0.45 mm.

Proprietary EPDM penetration flashings are detailed in 9.5 Boot Flashings.

8.1.1 Flashing Durability 

Where a flashing is hidden or is otherwise difficult to access for maintenance or replacement, or it requires cladding to be removed to replace the flashing, it must have durability for the life of the building or not less than 50 years. All flashings should be made from materials with a durability expectation not less than that of the cladding.

In some corrosive environments, stainless steel or non-ferrous metals should be used for flashings. All metals must be checked for compatibility with the roof material. (See 4.9 Compatibility and 4.9.4A Interactive Material Compatibility Tool)