Not required., Euroclad Architectural internal/ external butt jointed 0.9 mm aluminium flashings., Euroclad Architectural internal/ external butt jointed 2 mm polyester powder coated aluminium flashings., Euroclad Architectural internal/ external butt jointed 3 mm polyester powder coated aluminium flashings., Euroclad Architectural internal/ external butt jointed 0.7 mm steel flashings.