Assessment of Financing New Construction 425k € / Overall Financial Situation

The plan is to help with the masonry after work and on Saturdays, all electrical work done independently by my brother-in-law (a trained electrician), drywall, painting, floors, interior doors (my girlfriend’s father is a carpenter). Earthworks are done by a friend who works in road construction. That's the current plan. With "of course," I only meant to express that it is natural for me to invest a lot myself during the construction phase. Of course, all this will take longer than if a contractor were involved. However, we could temporarily move into my father's house, which is planned anyway. Therefore, additional costs for a rental apartment are basically not an issue.

It complicates everything. Lots of work done by friends and family. What if that doesn't work?

But since I am basically a rather thoughtful and safety-oriented person,

Honestly, after a few of your posts, I can't really understand this sentence. You are driving full speed towards a wall right now, and you only accept that with resignation if this here

But of course, it is not the intention to burden my family with my problems and the absolute last-last-last resort.

is only taken semi-seriously. Instead, your posts read like hundreds or thousands of others here, which I usually categorize for myself under the label "incorrigible."

You have already forged your plans and caught fire for this once-in-a-lifetime project. I wish you well with that, but without a sense of reality, it is doomed to fail, and then probably more than just your hard-earned income and savings will be lost.

If I were you, I would first try to make the calculations a bit more transparent. If this architect does not help you with that, then find another one, or speak, if you want, with a general contractor, because with such incomprehensible summaries

I arrive at the 425k euros when I deduct subsidies/grants from the calculated construction costs and, of course, the in-house work amounting to, let's say, 30k euros.

you only make it even more impossible for yourself to see reality clearly.

If—and that is a big if—this project is feasible for you, then only with meticulous planning and disciplined execution. That certainly also includes drastically trimming your current lifestyle and turning every penny twice over, because otherwise only my first-mentioned point helps, which you want to avoid like the devil the holy water.

So saving 30k is definitely doable.
Most of the trades are within family/friends and everything has worked out wonderfully so far. Besides the labor, we often get the purchase prices for materials, for example.
Also, we get all machines like the vibrating plate or concrete grinder borrowed for free, for example.

Overall, we still can’t afford 425k for 160sqm + basement (without slope) and you’re building 2 years later, so I really think that’s unrealistic.

What kind of architect is that anyway? We didn’t get an architect, for example.

Also, we currently have a net of 5200k and once kids come, it will probably be tight for us for a while too.

Sugarcoating won't help here. We planned 140sqm plus basement and slope in 2017, started at the end of 2018, and moved in in 2019.

From the forum's perspective, we built very unconventionally, or rather like in the old days. This means roughly estimated without execution planning, everything on a verbal basis and with minimal planning effort but maximum coordination effort, because every trade knew each other and also wanted to be commissioned in the future by our construction coordinator. In other words, it was possible for us to save about €50k by building this way. For example, we paid a ridiculous €6k for the basement excavation, transport, and disposal. And this applied to several trades. This brought us to €420k for everything (finished inside/outside) excluding the plot.

But that was 4 years ago and with 20sqm less living space.
Therefore, I would say from my own experience, if you want to go through it exactly like this, you are financially screwed.

What kind of architect is that anyway

And is his fee already included? That’s another 10% on top for full service.

And if he is also supposed to accompany the service on site with you: does he know about the many hands who are supposed to support you?

... Electrical work completely done by brother-in-law (trained electrician), ...

How is the warranty actually handled in such a case? Recently, a house in our area burned down due to defects in the electrical installation ... Is it enough – in case of emergency – to prove that a professional carried out the installation?