Sealing

Although the design principles are the same for all metals, the method of sealing penetration flashings depends on the metals in use.

Galvanised steel, zinc, and copper can be soft soldered, but not aluminium, unpainted and painted Z and AZ coatings. The acceptable method of sealing these materials is using either a neutral cure silicone sealant or a butyl sealing tape. These sealants should only be used in conjunction with mechanical fasteners.

The penetration flashing should be made weathertight without relying on sealants as a first-line defence against water ingress. When a sealant is used to prevent the accumulation of dirt in the joint, the excess sealant can be removed by a plastic spatula or purpose made plastic scoop, because excess sealant collects dirt which can cause corrosion and it is unsightly.

Sealant should always be used in conjunction with mechanical fastening and be applied between the two sheets to be lapped before they are fixed. It is unacceptable to apply the sealant after the joint has been made. See Sealants.