Refinance existing loans with a construction loan

That's also how I would have calculated it again. Why should a bank finance more than the house is worth? —> Loan-to-value, not costs or market value
And then there is hardly any buffer left for cost increases. I would also reject your financing with kitchen and credit payoff in our house.

Because they make money with it?
The higher the risk and the loan amount, the higher the interest rates and the more money the bank makes.
Of course, only up to a certain limit, that's clear.
Also clear is that banks naturally only pick out the easy requests.
At 95%, ING wouldn’t give us 1.1%, right?

How do you calculate? I am a construction financier and calculate as my bank does. The bank can only state the lending value after creating an appraisal (this must be done because it is no longer a small loan). Everything else is calculated very roughly by a computer.

Is 20% often deducted for a new build as well? Then you would almost always currently need around €100k in savings just to get a 100% financing?

Call up the Baufinanzrechner of ing, enter your values and specify the Zinsbindung. That usually fits quite well in normal cases. Provided your income matches the loan or the repayment.

How do you calculate? I am a construction financier and calculate as my bank does. The bank can only say the loan value after preparing an appraisal (this must be done since it is no longer a small loan). Everything else is calculated very roughly by a computer.

426000 + 20k external facilities + 20k ancillary construction costs + 18k equity/EL + 155k land
is 639000.
Minus 15% is 543000
Required loan is 466000
Makes 86%.

I think I gave a wrong value for the house earlier. Not 399000 but 426000.
Working only with a mobile phone is not so optimal.

Because they make money from it? The higher the risk and the loan-to-value ratio, the higher the interest rates and the more money the bank earns.

At some point, you reach an area that money can no longer pay for. Mezzanine (i.e., equity-like subordinated financing without collateral) is around +/- 10%. You have no security for the high loan. The bank may only value 60% of the loan-to-value as collateral. And your overall situation does not justify placing your other liabilities on the house. Enough banks stop at 100% loan-to-value ratio. And that is a good thing. That is why we almost never finance over 100%.

Is 20% often deducted for a new build as well?

Yep. There's no difference compared to existing property - why should there be? In the case of existing property, the lower price compared to a new build reflects the fact that it is a used property. Some also calculate with a 10 or 15% safety discount.