Clearances

There must be enough clearance between the edge of a vertical flashing or a notched flashing and the cladding to ensure the edge of the flashing does not mechanically remove protective coatings on the cladding. Similarly, the edges of cladding running parallel to flashings, such as at a window head, should have clearance to avoid mechanical damage and allow drainage.

Having the lower edges of flashings apart from the surface they cover helps to improve the cut edge durability of the flashing. Kick-out barge details are preferred to bird’s beak barge details for the same reason. The size of the clearance is not critical, but typically it is more than 5 mm.

For vermin flashings, both the clearance and the slope should be minimised to ensure the opening size at crest level does not exceed 7 mm.

Window Head

Window-Head