Flashing Expansion Details

Expansion should be considered at the design stage, and the flashing details should be included in the working drawings and tender documents. As flashings cannot move in the lateral direction without stress, they should have some provision for longitudinal expansion when their length exceeds 18 m, or for lesser distances for visual flashings such as fascias and facades.

When using an expansion joint, independence of movement should be assured by the omission of any fixing through both sides of the joint. Preferred and acceptable slip joint expansion details are shown in Apron Slip-joint and Ridge Slip-joint. Soaker expansion joints relying on sealant should not be used.

Slip joints require sealants, not to make them weatherproof, but to exclude dust and dirt from two close fitting surfaces, which can retain moisture by capillary action and cause corrosion. Rivets and other fasteners must not prevent movement of the slip joint.

Apron Slip-joint

Apron Slip-Joint

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Ridge Slip-joint

Ridge Slip-Joint

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