The building code of Australia & the Australia Standard (AS3740-1994) outlines the following as the minimum requirements for waterproofing of residential bathrooms:
Waterproofing the full floor within the shower recess.
At least 100mm over the hob or step down onto the bathroom floor should be waterproofed.
At least 150mm up the walls inside the shower walls needs to be waterproofed.
The vertical angle between any two walls in the shower needs to be waterproofed up to at least 1800mm high.
The entire bathroom floor needs to be waterproofed if it's timber flooring, plywood or particleboard or if it is above the ground floor of the house.
To ensure the best protection against water damage, it is a good idea to go beyond the minimum requirements by ensuring that all walls and recesses are waterproofed as well as the entire bathroom floor.
Some councils will require that waterproofing by done by licensed waterproofing applicators so to be sure, you should check with your council before any waterproofing is commenced.
What is the process?
Before waterproofing can begin, all surfaces must be correctly prepared and primed. Any drainage in flooring as well as joints between walls & floors are extremely important areas. As the waterproofing membrane is either painted, rolled or sprayed on, the surface must be completely smooth and free of any loose particles which may affect the consistency of the membrane.
A webbing or bandage reinforcement should be fit into all of the internal corners of the shower floor recess and any other edges or corners in the wet areas.
The waterproofing membrane product will then be applied by either brush, roller or sprayer to all surfaces. A minimum of two (2) coats is required and at least an hour or two of curing time will be needed between the first and second coat. Each coat should be applied in a different direction, i.e. Horizontal on the first coat and vertical on the second to ensure a liberal application which covers the area sufficiently.
The curing time will be a minimum of 24 hours before any further works can be done on this area to ensure the membrane will function to it's maximum ability.