Construction loan without building permit possible?

Of course you can finalize it. You just have to be aware that then you have a financing from which you can no longer simply get out.

The banks want to check what they are financing. So plans, contracts, etc. With this volume, you won't get around it.

The banks want to check what they are financing. So plans, contracts, etc. With that volume, you won't get around it

You don't have to have everything finalized to complete a financing. This is called a disbursement requirement and must be in place for the first valuation. Besides, the OP has already written that he has an offer from the bank.

You are not coordinating with project developers but with construction companies. Regardless, only the bank can tell you what you need to present in order to get the contract signed; usually, these are plans and building descriptions as well as a cost breakdown. A building permit is rather unlikely. However, it should be clear that if you sign next month, construction will very likely not start until spring 2021. Then you will pay commitment interest - for us, that was 3%.

The new building is supposed to have roughly the same dimensions as the demolition object.

Sounds at first glance not like a standard house in a new development area, but rather a bit more special. Therefore, I would first obtain the building permit, as this can take a long time. It depends again on the city. As an example: I had to wait over three months just for dormers in an existing building.

The low-interest loan quickly becomes expensive if you have to pay the [Bereitstellungszins] after 12 months have passed. I would not take out the loan yet.