Horizontal Metal Cladding

The weathertightness of horizontal cladding is entirely dependent on the flashings of cladding and penetrations, and because it is susceptible to the accumulation of condensation a cavity is required for all lined buildings.

It is recommended to seal horizontal laps with lap tape when they are enclosed in a cavity that is subject to condensation. This is needed to avoid the build up of moisture at the lap that can occur when dirt and condensation collect, which can increase the time of wetness and cause corrosion of the coated steel cladding.

This method requires accuracy and skill to make a neat joint, at what is a vulnerable point, and which should be sealed to prevent water ingress. Because this joint relies solely on sealant and cannot be mechanically fixed, it is not a recommended option.

To avoid slitting the sheets where in a single storey building, a double hemmed jamb soaker flashing can be continued to ground level behind the cladding—providing there is provision to enable water to drain clear of the building. This is not a recommended option unless there is a cavity behind the cladding. Multi-storied buildings should have a sill at each floor level so that soaker flashings do not need to drain more than one level.