Check with your current building codes/state codes, but it's usually 15" from the center of the toilet, not on each side of the toilet, which doesn't give you a whole lot more, but it is some!

Yes, a 30" space for a centered toilet is commonly required, which will give you almost 4 feet of vanity.

Have your plumber check the joists before you buy the vanity, though, as sometimes you have to shift an inch or two one way or the other to run pipes without cutting structural stuff.

I would have the vanity right up against the wall. You are already losing some space for your vanity, why lose another 4”? That is what you would need to make that space between the wall and the vanity accessible for cleaning.

I am having a hard time understanding your decision to switch the toilet and the tub positions. You create an almost inaccessible 17” space at the end of the tub, as well as losing some vanity space. You gain a tub that is not quite centered under a window, just noticeable enough to bug me every time I was sitting in there, if it were my home. Some also have an idea that seeing a toilet from an open bathroom door is some kind of design sin. That may also be behind this move. But, since the bathroom is simply too small for the luxury of many things that are possible in larger rooms, I question if it is worth moving plumbing and a wall to make this switch.

If you do find it worth it too you, I would suggest that you consider using that 17” space wisely. I am guessing that you plan to put shelves there. Possibly a lower shelf holding bath towels with decorative items on the upper shelves. This is handy and looks nice, but it is nice to have hidden storage for messy supplies, too. I would put one or two shelves there at the end of the tub. Above that, put a kitchen pantry pull out into a cabinet above the shelves. It pulls out to the side for access. Because of that, it has to be positioned so that it clears the top of the toilet tank when open. But it will hold a lot of TP, bottles and toiletries. Since this is the family bathroom, you might one day find you have four or five different shampoo and conditioner bottles that need storage space.

Still looking at this 17” space, consider the area below the tub deck. You could put a shallow cabinet there that you can reach from the toilet. So, a place for a few rolls of TP, or the toilet brush and cleaner. Your limitation in this spot is that you have to have room to open the door to the space without hitting the toilet. So, you might need two doors here. Or put in an open shelf here like I have at the end of my vanity, only shorter because it ends at the tub deck height.

Hi, thank you for your thoughtful comments. We’re moving the tub and toilet to avoid looking at the toilet straight away but also because we have a 30” tub now and really want a 32” tub….so our existing toilet would either be too close to tub or not centred under the window. Added to that it’s an old toilet so we need to move from a 10” to 12” rough In, which isn’t possible with the joists below (we know we could stick with a 10” toilet but have decided against that). And yes, we are going to put shelving to the left of the shower, I appreciate your suggestions about the layout of this. I’m happy to be considering all of this now before we commit to our plan.

Yes, a wider tub can be very important. A too small bath is not relaxing. Let me show you the other leg of my vanity. It shows that a pull out can be added to any tall, skinny space. My cabinet leg is only 8” wide and there is not a lot of space in my pull out, but it holds curling irons and bottles of hair care bottles. With 17”, you would have serious storage space. A pull out can be made using two drawer pulls top and bottom. With my little one, we just used one on the top.