Hello,
so we are currently also planning a bungalow and regarding the utility room I have to say that we have actually already seen small ones.
However, really without a large buffer storage. With a tankless water heater. And an air heat pump.
As soon as heating with gas is planned, I also consider the utility room too small. And a new gas heating system, "alone" no longer possible. (New regulation from 2018)...
Otherwise, personally I would not plan with bunk beds. But that is just my opinion, because I think eventually you get "tired" of it and in old age nothing anyway. But you can still do quite a bit with a 12 sqm room.
You should also really calculate how much you can actually save with less living space, because certain expenses you simply have. Whether 90 or 100 sqm...
And if you can do a lot yourself, 10 sqm more do not end up being a huge amount of money. (Sure, with materials, foundation... but for heating, windows, electricity the size of the rooms really does not matter much, right?)
Personally, I suspect you can really only save if you and your family and circle of friends can do a lot yourselves. And if you start out with a too tight budget and in the end don’t make it... you wouldn’t be the first to fail.
And I also find it dangerous to overestimate yourself.
If you want to do a lot yourself, you should not think too much about whether you can stick to a certain budget but rather plan with a reasonable budget and ultimately hope you manage to do it yourself and maybe won’t fully need the budget.
I mean everyone surely has the thought to keep their financing needs as low as possible, as we do...
I can also understand the room layout personally.
We have a plot or the house location, where exactly this room layout is absolutely right.
Regarding your living area or in terms of statics, I have the same questions concerning our bungalow but I believe only the architect or a structural engineer can really tell us.
Everything else beforehand is interesting but not really relevant. Because what the structural engineer says then is the only thing that counts, not any "this could be possible"...
So I can only advise you to have the house planned or have a house offer made and then you will see what is realistic. And then you will also know if it makes sense for you to buy a building plot.
We have done that anyway and are now at the phase: plot available, but with whom and when we will build is still open.
And if you have the desire and can realistically assess your own work, then just stay on it and talk to tradespeople or construction companies and get different opinions and form your own from that.
Good luck.