wowed, I agree with your response, and it's interesting to me. I would want at least sound, if not visual, separation, between a lavatory/dressing area and a bedroom. It's interesting to compare the bedroom/lavatory area/toilet and bath area layers to a palace set up: the anteroom, the throne room (no pun intended) and then private quarters. In the same way, access and function are layered. I think most users would agree this sort of layering is a good thing. Contrast this to the evolution of design of the kitchen/dining/family room area of a house. For me, sound separation of activities (eg., tv watching vs. a conversation in a dining room, or relaxing in the family room without the din of dish stacking) or visual separation (chatting with guests in the dining room while not worrying about how the busy food prep area looks) or even olfactory separation (reading a book in the family room while onions are sliced and sauteed in the kitchen). The grand, open flowing floorplan for these areas is popular, but for me, I prefer a little segregation, especially as the number of users and potential simultaneous uses goes up. Seems to me, as the average household size has shrunk and more people are living in a house of only 2 or 3 people, sure, the open floor plan can work. But for now at least, I want a little bit of separation of activities, and I like my "antiquated" floor plan, with separate kitchen, dining room, family room (tv) and living room (piano). A tv and piano in the same room would be a nuisance for us. So I guess on a more micro level, I'm looking to separate activities in the bathroom. But I agree, if in the process of pulling them apart and relocating them, I mix grooming and sleeping, well, yes, that would be a disastrous unintended consequence! responding to another post, I don't know why that link didn't work, here is the direct url: http://www.farrow-ball.com/Company/FBStyles.aspx?language=en-GB&style=5

Exactly what catbuilder has said. Waterproofing is needed in wet areas only. Cement board can get wet and is (I believe) usually used correctly with a waterproofing behind it (such as plastic membrane) or can have waterproofing applied topically. (I believe some waterproofing is even approved for application over drywall, though I haven't used it myself.) So around a sink area, drywall is just fine (normal even). You don't even have to have a backsplash of any kind, though it's a good idea if anyone is washing faces or might splash a lot. Around a tub or especially a shower, you need waterproofing either in the form of a plastic membrane or topical membrane or topical liquid membrane.

you need a splash even without kids. Actually, you could have your vanity without a splash, similar to mounting a pedestal lav (sink) all by itself. As a builder I would need to know beforehand depending on source of the countertop. My fabricator would cut the counter deeper to fit to the wall with caulking. Prefab slabs are not as generous and may require more filler work to cover any gaps. Faucets splash water even without your assistance. Its not a flaw, but a function of water falling from the spout to the drain.

I really like that last one. I think it would look great!