Wall underlay

As water may drain down or be held by the wall underlay, it is fundamental that builders install the underlay to ensure that it forms an impervious drainage plane that stops water getting to the vulnerable bulk insulation or timber frame.

Wall underlay must be installed taut, laps must have sufficient cover and should be taped, any penetration or tear must be taped and sealed and the underlay must exit the assembly at openings that will allow water to drain out. 

For cavity claddings, an additional batten or taut tape is required for battens spaced at more than 450 mm to hold underlay in place and prevent it billowing into the cavity.

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Wall claddings

Scribing to bevel-back weatherboards (see below for the six steps).

Updated: 7 December 2016