Financing after contract signing - experiences?

Hello everyone, we are about to sign the contract and have now received the information that the construction including all applications from signing to handover of keys currently takes about 27 months. Since there are 3 different payment deadlines with the construction company, the full amount is not due at once. I am now wondering whether we should apply for the financing final approval later so that we do not have to pay commitment interest. Of course, I would obtain a bank confirmation before signing the contract. Has anyone had similar experiences or can give me a tip if this makes sense? PS: We have already purchased the plot of land and it would be handled separately.

27 months is extremely tough. Is there no possibility to change the construction company? Even considering the Corona crisis, that is an extremely long time. As far as I know, the bank usually grants 12 months interest-free.

Yes, that is also one point.
What I have to say about it is that we want to build a prefabricated house. According to our architect’s statement, they themselves had between 18 and 20 months outside the Corona period.

We are currently inquiring with other providers.
However, some are already at around 23 months.

Of course, I would obtain a bank confirmation before signing the contract.