Bathrooms are the major wet area in the house and it is important that the bathroom is correctly waterproofed in order to reduce the risk of structural damage occurring as a result of dampness, water leaks, or condensation.

Requirements for Waterproofing Bathrooms

The Building Code of Australia and the Australia Standard (AS 3740-1994) outline the minimum requirements for the waterproofing in residential bathrooms.  These requirements include:

• 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

However, to provide the best insurance against water damage, it is a good idea to go beyond these minimum requirements and ensure that all of the walls within the shower recess are waterproofed as well as the entire bathroom floor. To get a visual on this, see these photos of bathrooms by trade professionals.

Be aware also that some councils will require that waterproofing be done by licensed waterproofing applicators so you should check with your local council before any waterproofing work is undertaken.

The Process of Waterproofing

It is vitally important that when you undertake a bathroom renovation all the surfaces within the bathroom are correctly prepared and primed.  Especially of importance are any joins between the wall and floor, between the walls themselves, and around any drains in the floor.  Ensure that the surfaces are smooth and free of any loose particles, which may affect the integrity of the waterproofing membrane.  A polyester reinforcement mat should be fit into all the internal corners of the shower recess, such as the junctions between the wall and floor, the hob and the floor, and the corner formed by two walls meeting.  The waterproofing membrane will then be applied to all surfaces.  Once the first coat has been applied, an hour or two will be required before the second coat can be applied.  The second coat should be applied in a different direction to the first – for example, if the first coat was put on vertically, the second should be horizontal.  Do not use the bathroom until the waterproofing has had a chance to fully cure – this can be as long as five days, depending on your climate.