Hi @AT2,
Thank you for your question and welcome to the Bunnings Workshop community, it is fantastic to have you with us.
Please note that waterproofing is a licenced and regulated industry with high standards for workmanship. For this reason, to ensure you are in line with relevant building codes, it may be a good idea to have a suitably licenced professional carry out this work for you.
The best bathroom waterproofing product I am aware of is Crommelin 15kg Pro-500 Undertile Waterproofing Membrane. This is painted on to the substrate to form a thick uniform coat without any gaps. Crommelin 5m Waterproofing Tape and Crommelin 90° Flexible Membrane Reinforcing Internal Corner are also used to reinforce the corners and joins.
You might like to check out How To Waterproof Your Bathroom Floor for some guidance.
Let me know if you have any further questions.
Jacob
