It's not a simple debate between what you want/need more or less....understand that this a regulatory thing.........if you are dealing with a building permit then it's pretty cut & dry - as the BCA reads, a separate trough is technically required to consitute a laundry....happy to be corrected in my interpretation in this regard but we have had to deal with this exact issue on a few occasions....... But if you are doing just an under the radar laundry reno/refit (no permit) then potentially you can get away with none, but you'll of course need to practically connect the washer into the drainage somehow, which still requires an isolated trap set-up, that technically will be illegal. No you can't just connect straight into a sewer waste as if the connection fails and their is no water trap it would be hazardous (not to mention unpleasant) to have exposed sewer gas. If it's in a kitchen an can connect a washer to a sink waste (similar) to the dishwasher) then arguably that could be passed. The easiest way is to fit a small trough next to the washer that even if you develop a cover for so you can use the area as bench space. It then keeps flexibility and everything above board/compliant for future resale.....

You should create the bathroom that works best for you. I have no family but for me a bathroom with no tub is a big no no because I like to have a bath occassionally. Yet I've walked through many homes recently in which the main bathroom had a shower only. A lot of people find better mileage with an oversized shower. Do you ever take baths? Do you ever have small children in your home? Do you need a tub to wash the dog in? Are you going to ever sell this home to a family with small children? If the answer is no to all of those then it may be a better use of your space to put in a shower only. I disagree that a shower over a bath is a big no no in a family home. If you have children under 5 a bath is a must. You cannot bath a small child in a shower [easily]. I've yet to meet anyone that absolutely hates a shower over a bath who wasn't an octagenarian and even then their objection is the fact their balance isn't what it used to be and they find getting in and out physically difficult. Go with what works for you and your situation. Anyone after you who buys this house can put it the way they like it later.

This is a gorgeous reno, my favourite this year.

True the standards will be different, but as far as I know, the standards in Australia for waterproofing tubs only state what the outcome needs to be, not necessarily the exact equipment used to achieve it. I think something like this on the market would solve a problem for many people. I've just seen horrendous installations on NEW buildings that included MANY APARTMENTS especially where water clearly runs down between tub and wall and not to standard at all. I can't believe what builders get away with. The way I found out about this stuff is because I've pretty much exhausted my options. Scrolled till my eyes could scroll no more! :) Over many days. I saw a bath on Temple and Webster of all places which stated that it comes with an adhesive tile bead, and I was like, what is that?! I am now actually considering that tub, so I might not need to get a separate thing. But otherwise I was thinking another type of trim or flange attached to the tub could very well do the job just fine. I'm still very confused why island baths are more often offered as a wider bath and flange baths (and especially anti-slip ones clearly concepted to be shower baths) are narrower. I'm guessing they know what sells, but it goes against my design instincts!