Notary before loan commitment

Good morning dear community!

Our house construction project is entering the "hot" phase, more precisely the financing phase. We have an offer from the Sparkasse (main bank) in combination with an ISB loan (already approved). We were at the Sparkasse again on Thursday and are supposed to go to the notary on Tuesday to have the mortgage registered for the Sparkasse and ISB.

We have a binding loan agreement from the ISB, but _not yet_ from the Sparkasse; the contracts are being prepared, we are told.

Is it common to order the mortgage before a written loan approval?

[I would wait. There is a deadline for acceptance and a withdrawal period upon signing. Choose the date so that you could revoke in case of emergency]