First fork in the road: Has the plan already provided for the exception?
§ 31 Absatz 1 BauGB describes exceptions that are explicitly provided for in the development plan (Bebauungsplan) in terms of type and scope. Such an exception is therefore not a freely invented leeway for any unsuitable project. You need the binding plan including its textual provisions and the passage to which the desired exception is to relate. [B31]
For preparation, an understandable comparison is sufficient at first: What does the plan stipulate, what is actually to be built, where is the difference? A marked excerpt with clear dimensions is more helpful than the general claim that the neighbourhood looks similar. Whether neighbouring development is comparable and on what basis it is permissible remains a separate question.
Second fork in the road: It is about a dispensation (Befreiung)
For a dispensation under paragraph 2, § 31 requires, among other things, that the basic principles of the planning are not affected. One of the reasons listed there must also be present, for example an urban-planning justifiable deviation. In addition, the deviation must be compatible with public interests having regard to neighbouring interests. A personal wish or a reference to higher construction costs does not replace these prerequisites. [B31]
The current provision also contains in paragraph 3 a special route in favour of residential construction with the consent of the municipality. It can concern an individual case or several comparable cases. Neighbouring interests and public interests remain relevant here as well; the provision specifically names additional significant environmental impacts as a contrary case. The prerequisites from paragraph 2 must therefore not simply be written across all routes without distinction. [B31]
A source that only summarises an earlier version may overlook this current distinction. For the specific project the correct legal basis belongs in the technical coordination.
A decision with two design variants
In the hypothetical case a couple want a larger dining area facing the garden. The planning presents two variants: one within the provisions and one with a precisely specified deviation. Both fulfil the housing wish to different degrees. For the deviating variant the affected plan content and the conditions to be clarified professionally are identified.
The couple do not decide prematurely that the dispensation will be granted. They assess whether the plot remains attractive with the compliant variant as well. If only the deviating solution is viable, this dependency is expressly taken into account individually in the contract preparation. A seller’s statement is not official evidence for this.
In the end there should be a decision template that brings together the plan rule, the deviation, the possible route and the remaining uncertainty. It does not replace the examination by the competent authority nor a permit. But it prevents the purchase of land, financing and design planning from tacitly building on a still unresolved claim of exception.