Dear All, Ask your ID the below question: How is the waterproofing system for the toilet flooring done (for HDB renovation)? That's all. Its that simple. When you are Id shopping, ask all of them to answer this question and from their answers, you briefly know who really have the knowledge and experience to their work. By doing this you'll also show them that you do have knowledge in regards to renovation, hence they'll be more careful when giving you a quotation and do not dare to show their "cai dao" The answer you should be expecting comes in 4 steps. Some will tell you 3, some 4, some don't even know the materials. PM me for a more detailed and accurate answer to use as a guide. Regards, Darren