Key legal question
To what extent may immission-mitigating measures be required from the builder under § 146 BauG and § 61 KBR?
Extracted holding
The builder need not do everything technically possible; it is sufficient to take what is technically possible and reasonably exigible.
Extracted reasoning
The rules require buildings to be designed, altered, and maintained so that they create as little immissions as possible, but only within the limits of what can reasonably be demanded of the owner.