Hello,
so a 12-month construction interest-free period is standard at most banks.
some already offer 18 months or even 24 months free of charge.
at some, you can also "buy" a longer construction interest-free period in exchange for an interest surcharge.
just have your broker calculate what 24 months of construction interest-free time would cost, and then you have the comparison; it might be that the bank that is cheapest with 12 months is different with 24 months.
If I were you, I would also have it calculated with Excel to see what makes sense:
how does the interest (surcharge) compare to the commitment fees?
because usually the funds for: land, basement/floor slab, shell construction etc. are used relatively quickly, meaning if you already use 70-80% of the loan in the first 12 months, then the costs for the rest are manageable... and then it's better to pay a lower interest rate for 20 years than to save the 3000€ in commitment fees at the beginning but pay the bank 6,000€ more in interest over time.
as I said, only an Excel spreadsheet helps here, to see when which funds are drawn and what you actually have to pay in commitment fees