From where is the border distance measured?

From where is the minimum distance of a building from the boundary measured? Assuming the eaves height is 4m, the ridge height 10m (gable roof), and the factor (Niedersachsen, WA) is 0.5. Must the outer wall then be 2m and the ridge 5m away from the boundary, or must the outer wall already be 5m away?

From where is the building's boundary distance measured?

It does not matter, differences are direction-independent A_B or B_A are equally large.

Assuming the eaves height is 4m, the ridge height 10m (gable roof) and the factor (Lower Saxony, WA) is 0.5. Does the outer wall then have to be 2m and the ridge 5m away from the boundary, or must the outer wall already be 5m away?

Assuming we are talking about one and the same wall - then it naturally only has one boundary distance. The gable wall in the example would then have 7 m average height and would probably have to retreat 3.5 m from the boundary. Wouldn’t this actually belong as a follow-up question in ?

Is each point on the building considered individually, or must the structure as a whole maintain the distance determined by the highest point?

Is every point on the building considered individually or must the structure as a whole maintain the distance determined by the highest point?

Oh, that would have been a question for , who hasn't been active here for quite some time. I’ll hazard a guess, without any guarantee: Simplifying, you can imagine each wall as if it were (of course distorted in height by the respective factor) virtually felled like a tree onto the boundary. No point of this wall may then lie "offside" ;-) What is it about anyway: do you want to maximize the boundary distance, or do you suspect someone else has miscalculated to your disadvantage?

I want to verify the seller's information using a site plan

I want to verify the seller's information based on a site plan

Then consider that the game only works with knowledge of reference elevations. In addition, state building codes are subject to change, for example regarding the elevation weighting factor or the privileging of outbuildings. As a layperson, you can quickly make an incorrect assessment. Is it decisive for your purchase whether you are allowed to build an extension four meters twelve wide or only three meters ninety-eight?