Single-family house optimization and planning (180 sqm + attic without basement)

I can only advise to plan with the right furniture. You don’t have to finalize the design now, just work with the correct sizes. Additionally, always pay attention to sufficient traffic routes. Nobody wants to run a new slalom. If you don’t deal with the furnishing now, it will be like in a rental apartment. The rooms are there, and then you start looking for suitable furniture.

A few more things about the floor plan:
- What is the door on the left in the garage for?
- The wall between the utility room and the garage is drawn way too thin. It is important for the closure of the thermal envelope.
- The garage width is suitable for one car and bicycles, but not for two cars.
- The door from the garage to the utility room takes up a lot of space there.
- How are you designing the toilet in the garage so that the pipes don’t freeze in winter?
- Swap bathroom and office on the upper floor for shorter pipe runs to the utility room.
- Start over again with the bathroom itself.
- Next to the bed in the master bedroom there won’t be 60 cm. This is very, very little! But there is space at the foot end to dance a waltz, since the drawn-in wardrobe in front of the window won’t exist.
- The fireplace in that position could cause problems because it might collide with the ridge.
- I would also delete the mini air space at the entrance right away.

For the budget you have, you need to build simpler. You have a ton of gimmicks that bring very little but cause a lot of extra costs. You have a lot of walls (including load-bearing ones) that are not directly above each other. The corner cube that costs a lot of money for the additional space offered. Corner window in the bedroom, which nobody really needs. And much more!

I probably would have even tried to realize the project

Have you ever questioned the collaboration with your "architect" (these quotation marks are intentionally placed with regard to the floor plan) in light of your previous experiences? A cost overrun of 25% is quite significant.

almost before the building application

And with the cost estimate and cost calculation, didn’t the "architect" notice this €100K delta?

We are foregoing French balconies

If something like that was being discussed in your area, you are talking about an apple while the OP posted a pear. Completely different house type and costs more. More living space costs more.
The OP dreams of a pear but can only afford an ornamental apple.

But I meant us with that.

Then please post the real design that is also worthy of discussion.
Why should one start a discussion here and now, without a building window, about optimizing a house that will never be built?

Unfortunately, you also have to pay for the foundation slab and incidental building costs. And the incidental building costs are basically always the same up to a certain size. In my opinion, the OP is talking about my total budget. Therefore, your comparison is a bit flawed when you say that you also manage it. Besides, it seems you are still dealing with planned costs and not actual costs. I don't understand why the prefab house manufacturer should make it especially cheap now. Building costs are roughly the same regionally. The standard and the wishes determine the price.

I just understood from the OP that it’s only about the pure house costs. If it’s the total budget, it’s going to blow up even more than expected. For the house costs, we have a price guarantee, so I don’t see why planned and actual costs should diverge at this point for us.

I am well aware that the OP doesn’t have French balconies. It was simply an example.

Have everything here. From the architect contract to the DIN 276 cost estimate of the same. 100k over the discussed maximum budget.

That is already a remarkable lack of professional experience that enables this double error: only noticing such a significant budget overrun when adding it up, and drawing in furniture & co. without realizing that there is no space around them. Am I correct in assuming that this expert has already planned the parents-in-law’s house and has since been detached from reality as a university professor?

I don't think the draft is such a bad starting point. You could first radically remove all bay windows and smooth out the walls; that already saves expensive roof areas on the ground floor and creates space for the dining table. Also erase the fireplace there and it becomes a living room.

In the upper floor, in my opinion, one should go through it with a fine-toothed comb. The bathroom is a disaster. Even if one might find it original at first glance, in the long run it is oppressive and uncomfortable. What is the advantage of this combo bathroom? Basically, you have a bathroom with 4 sinks without a tub and hardly any space to move around. Is that supposed to be a second toilet at the top right? That’s nonsense. Even if there won’t be a bottleneck for brushing teeth and toilet use, you still stand in line for the shower. Having a second shower with a wall doesn't really help enough for me to skip it. I would plan the children's bathroom back in, because if you’re honest, you want it and not this crutch. Having a child sleep with their ear right against the bedroom wall and only light from one side isn’t great either.

The room width for the bed in the bedroom at 3.26m shell construction is very tight. That leaves a walking space of about 60cm for a 2m bed. That’s very narrow and you quickly end up nose to wall when getting up. The space for wardrobes is quite considerable though. Do you need them?

Overall plenty of wishes for the upper floor. You will have to swallow some frogs. But this bathroom frog would be too big for me – maybe it’s enough to plan a partition wall and you can manage with 2 small bathrooms? Otherwise, here’s another proposal, with different frogs ( )

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The main goal was separate bathrooms and moving the children's ears away from the bedroom. However, you lose wardrobe space and one child has a north-facing position. I still think it’s worth considering.

Oh, and you should keep an eye on the depth of the stairs. With 2.65m or so, it probably won’t work with a landing. Also the question if you’d allow yourselves an open staircase to the living room with two kids?