Average wall height in flat roof carport

Hello everyone,

I am looking to find out between which 2 points the average wall height is determined for a flat roof carport (in Berlin). So far, I have always assumed that the average top edge of the roof may be a maximum of 3m high, but that does not seem to be entirely correct, since it is the wall height and not the building height. This would be convenient for me, as the carport must have a total height of 3m due to controlled residential ventilation intake on the house wall, and there is a slope towards the property boundary across 2 parking spaces. So I would need a total height of just over 3m. But what does that mean specifically? Bottom edge of the parapet? Post length?

Do you have any practical experience or possibly a source where this has been documented?

Thank you!

I think - and could say it more precisely - that here the top edge of the parapet represents the eaves height of the penetration of the fictional wall through the roof covering.