Attic division. How many rooms would you choose?

Hello everyone - actually I’m not quite in the right place here, we are not building ourselves, but will have the attic above our apartment converted by the landlord. But I would be very happy if someone still replies! About the roof: it is 35 sqm of "usable" space (actual floor area 55 sqm), the slope starts directly at the floor, it is relatively high - about 5 m. About the situation: we are expecting a child soon, we already have a small (10 sqm) room "downstairs" that could become a children's room, and would actually like a second child. Whether that works out is up in the air. And back to the roof: it is already decided that a small bathroom with a tub will be installed, that it will not really be bright, unfortunately (heritage protection). I am very much in favor of two larger rooms (a living room, a children's room), hubby also wants a living room and two small rooms. His only argument for that is that the children's room would otherwise be "too big." I think the sloping ceilings can already feel oppressive if it is made too compartmentalized; besides, 35 sqm is simply too little for a bathroom and three rooms. What do you think, what experiences and tips do you have?

Is there a building permit for the project?

Hi,

so I’ll try to organize the whole thing a bit. Maybe I’m right in some places:

You currently live in an apartment and an attic above you is supposed to be converted for residential purposes.
Your current apartment includes (estimated) 1 living room, 1 bedroom, and 1 children’s room (10 sqm) + bathroom and kitchen.

In the attic, there are 35 sqm of living space (area without roof slopes I’ll ignore for now) available, of which a part (10 sqm?) will be used for a bathroom with a tub. That leaves 25 sqm, with the stairs also taking up some of that. With two rooms (one as a living room) it will be quite tight there – in my opinion, three rooms are impossible.

I would divide the entire apartment as follows:
lower floor: the living room becomes the parents’ bedroom, the parents’ bedroom becomes the 2nd children’s room – 1st children’s room remains
upper floor: the bathroom with tub + living room (though the use of the bathroom here can be debated)
Thus you have the sleeping rooms on one level and the living area separate from them.

Background:
With a small child (newborn) you may have to go into the room more often at night. Always having to overcome a staircase (half asleep) as mom or dad can be dangerous.
Speaking of danger: the stairs should always be secured by a stair gate (at the top AND bottom of the stairs) – otherwise you can expect to test your children’s flying capabilities.
Second reason for the layout from personal experience: Our older child (3.5 years) almost every night goes on a little walk. This usually ends rather quickly in the parents’ bed. Imagine, there is a staircase in between (see flying capabilities of the child).
Also – if the living area is separate and there is a reasonably good noise insulation, you can calmly pursue your evening activities without fear that the children will wake up because of it.
With the layout shown, all rooms (except perhaps the previous children’s room) would have a reasonable size.

Downside of the layout: Our little ones mostly play in the living room. This would then, of course, be harder to reach.

But this is based only on an estimated layout of the previous apartment.

First of all, thank you very much!
@ Bolzen: The building permit has been applied for as far as I know and will probably be granted routinely – this is a larger listed housing estate, and in the identical houses around it, about 1/3 of the attics are developed. I also trust our landlord, who is on the board of the owners' association and will (hopefully) be careful not to get into trouble there.
@ f-pNo: Yes, you guessed right! The size of the bathtub bathroom upstairs is not yet quite clear. (And yes, it has to be, my husband has terribly missed his bathtub for 3 years). In the "children's room" downstairs are currently our books, folders, desks, etc., for which there is no space elsewhere. I really did not express myself very clearly. One more piece of information that might be missing: We only have sloping ceilings to the east and west, to the right and left are the attics of the neighbors or neighboring houses. And what you say all makes sense; of course, we have already thought about stair guards. First of all, the child will stay with us in the bedroom anyway – if it stays with one parent (offtopic: This time it only worked with medical help and a lot of luck), it would then luxuriously have a sleeping room downstairs and a playroom upstairs. If the second one works out, your layout would certainly make sense. Honestly, right now I mainly want to make my husband understand that having a bathroom + 3 rooms upstairs really is simply not feasible or will lead to a rabbit hutch feeling – maybe he believes "professionals" more than me.

To be honest, my main concern right now is to make my husband understand that a bathroom + 3 rooms up there really just isn't doable or will lead to a rabbit hutch feeling - maybe he trusts "professionals" more than me. .

Thanks for the compliments - but I'm not a professional in this.
Maybe you should just show him the calculation with the square meters. I mean - whether the bathroom is 10 or only 7 sqm, in the end there remains between 25 and 28 sqm. This is enough for a decent living room but never for a living room + 2 small rooms (the stairs + small hallway would still have to be accounted for here). Rabbit hutch would, in my opinion, actually be the right term for that.