How much additional cost according to the structural engineer's calculation?

I meant wanting extra money for a black tank, if you already have a black tank in the original offer, according to your statement. I myself have a watertight :-D waterproof basement made of in-situ concrete

a bitumen coating is not equivalent to a black tank

a bitumen coating is not equivalent to a black tank

included in the house price was bitumen coating with drainage

This doesn't help you at all, dear... you don't have enough financial reserves for this project, period, end of story.

How much financial reserve should we have for this property?

how much financial reserve should we have for this property?

I say off the cuff, for 150 sqm with a full basement and waterproof tank in the earthquake zone (on the Alb or in the west?) 550k ready to move in is certainly realistic. Without land, without outdoor facilities, without kitchen. Depending on the exact equipment a little more or less. For 450k you certainly won’t get it built.

I say from the gut, for 150 sqm with a full basement and waterproof tank in the earthquake zone (on the Alb or in the west?), 550k ready to move in is certainly realistic. Without land, without outdoor facilities, without kitchen. Depending on the exact equipment, a bit more or less. For 450k you certainly won't get it built.

in the west.

I say from the gut, for 150 sqm with a full basement and waterproof tank in the earthquake zone (on the Alb or in the west?), 550k ready to move in is certainly realistic. Without land, without outdoor facilities, without kitchen. Depending on the exact equipment, a bit more or less. For 450k you certainly won't get it built.

we are in the west. ok, 550,000 and are no additional construction costs included like e.g. soil disposal?

a bitumen coating is not equivalent to a black tank

But that is exactly the waterproofing of a so-called "black tank".

Good luck