Financing feasible in the current situation? Single-family house 140 m² including basement

I can't imagine it, never Credit is always property-related

Advisor says that pledge swap / property swap is possible here, as it results in an increase in value for the bank (for a fee). Regards Marcus

I can't imagine it, never Credit is always property-related

Nonsense. A pledge exchange is usually possible without problems as long as the loan-to-value ratio does not worsen, and it costs a small fee (around 1000€).

Construction costs incl. basement: €500,000

How is that broken down? Basement as usable basement? How much living space?
Otherwise, your calculation is very realistic.

That means we would need another loan of €210,000.

Maybe you could do a property swap with the old loan?
But to your arguments: I just want to encourage you to think with my statements or questions.

We currently live next to a kindergarten. It is quite dilapidated and I think it will make way for a multifamily house in 2 to 5 years (our assumption).

But the multifamily house won’t be a monster in height, right? From how many floors would you have "respect"?
Probably there will also be some or at least one multifamily house planned in the new development area? At least then there is always a new playground in sight...

Especially because of the children, we would like a bigger garden, the needs have changed a bit

How much more garden would you have then? I am now reading about a plot of 250 sqm… or is it the garden of 250 sqm?

Parking situation is complicated (cul-de-sac, nowadays too many cars) and only one garage available

Phew, so without a cul-de-sac in a new development area parking isn’t exactly relaxed either.

Neighboring building is no longer occupied by the owner but is rented out. As a result, the interaction has greatly decreased

Well, that depends on oneself. It doesn’t have to be different in a new development area. Could be.
I don’t see the pressure to suffer at the moment. However, you are collecting arguments for yourself. And a new build always means something great, something new.
I would sell the property without a realtor, then you get more from the sale.
Talk to the bank about how they see the property swap.

Refinancing is one thing, but you still need more credit. If you don't take out the new 210k with the same bank, then the second bank moves into second lien position. I then wonder whether the banks will agree to that. (It could be; I've just always been told "banks don’t really like that," whatever that specifically means.) Whether that means worse conditions or some simply won’t do it, I can’t judge. Although financing with the same bank as before is, of course, also an option if they agree to it.

Just wanted to point out that when you say "we only need 220k additional credit," there might be more to consider than you perhaps had in mind.

€540,000 with an income of €5,800 is something you have to like. It's doable, but it's a big chunk of money to pay back.

Especially at around 40 years old.
How high is your repayment on the existing loan?

How does that break down? Basement as a utility cellar? How much living space? Otherwise, your calculation is very realistic.

The living space is 140 m². The basement is partially also intended as living space (office in the basement).

But the apartment building won’t be a monstrosity in height? From how many floors would you start to have "respect"? Probably a few or at least one apartment building is planned in the new development area? At least then there is always a new playground in sight..

I would already have problems with 3 floors. Currently, there is a kindergarten (bungalow type) there.

How much more garden would you have then? I now read about a 250 sqm plot… or is it the garden of 250 sqm?

The entire plot is 250 m² including garden. For the possible new plot, we are talking about a size of 540 m².

Phew, so without a dead end in a new development area, parking is also not exactly relaxed.

I described that a bit poorly. The dead end and parking situation refers to the current property.

Well, that depends on oneself. It doesn’t have to be different in the new development area. It can be. I don’t currently see the urgency. However, you do collect arguments for yourself. And a new build always means something great, something new. I would sell the property without a broker; then you get more in the sale. Talk to the bank about how they see the object change.

Yes, I completely agree with you. It can of course be that the neighborhood does not improve with the new property, maybe it will even get worse. You can hardly know that in advance.