Wet area design and construction principles must retain water in the designated wet area. BCA requires that water is not allowed to damage other building elements. This means that water is not allowed to enter other rooms or cavities. A shower recess is classified as a wet area, in its own right. Therefore water should not exit the shower area, even though it may be transversing into another waterproofed bathroom floor. This is common with hobless showers, where there is no or ineffective barrier angle.
BCA also states that the health and amenity of the occupants must not be adversely affected. Membrane applications below screed, with ineffective sub-tile drainage will result in bed saturation and bacterial colonisation. This results in mould concentrations.
Bathrooms are classed as wet areas in AS building standards, the purpose of waterproofing a bathroom is to keep water contained within the designated wet area. BCA Volume 2 governs performance requirements for Class 1 and 10 buildings. These areas must be waterproof or water resistance in accordance with AS 3740 -2010, under normal use. This means that water splashing onto the bathroom floor does not exit the room into the carpeted hallway through capillary action in the tile later and screeds. For this reason, Class 1 and 10 bathrooms, laundries and toilets are not required to have an overflow floor waste where the shower has been isolated or all surface water directed to the shower waste. Where the shower is isolated by a screen and barrier stop, direct stick floor finishes are permitted. The BCA and AS 3740 do not require screening of the floors. The drain provided may be a trapped palazzi gully, charged with water to prevent gas emissions from the sewer lines.
Unenclosed showers, with a walk through entrance are require to have a minimum 1:80 fall from the shower rose connection, in order to direct surface water into the shower drain. This encroaches into the main floor area, outside of the shower and must be supported by a minimum 1:100 fall in surrounding areas outside of this zone.