How to waterproof bathroom?

[JSLawrence]

Hi everyone, 

I have just had the screed layer removed from the bathroom floor and will be getting a concreter to come and pour the new bathroom floor which will then be sealed and used as a concrete floor and shower base without any tile. Can you please advise what sort of waterproofing needs to happen around the base of the wall prior to the concrete pour, and/or afterwards. Does some sort of waterproof membrane need to be laid and extend up the walls before the concrete goes in? The grey section along the edges is a very hard plastic that was the edge under the screed. Thanks.

[JacobZ]

Hi @JSLawrence,

Thank you for your question about waterproofing a bathroom and apologies for the delayed response.

As waterproofing is a licensed industry, I'd suggest you contact a waterproofing contractor for their guidance on the process.

With this being said, the National Construction Code (NCC) states the following in Part 10.2 Wet area waterproofing - Section 10.2.3 - Area outside shower area -

1. For concrete, compressed fibre-cement and fibre-cement sheet flooring, the floor of the room must be water-resistant.
    
2. For timber floors including particleboard, plywood and other timber-based flooring materials, the floor of the room must be waterproof.
    
3. Wall/floor junctions must be—
   
   a. waterproof; and
   
   b. where a flashing is used, the horizontal leg must be not less than 40 mm.

As you are looking to have concrete as the finished floor surface, a waterproof membrane can and should be installed underneath the concrete. The main reason for this is that to achieve a waterproof wall/floor junction, the membrane needs to extend 40mm onto the "horizontal leg", which in this case is the concrete floor. If you are looking to use concrete as a finished floor surface, having a strip of waterproofing around the edge of the room won't look particularly nice.

I'd suggest discussing the best way to go about this with a licensed waterproofer.

Let me know if you have any further questions.

Jacob