Hello Belray,
Your architect cannot assess whether the property can be legally subdivided.
A capable architect can make a statement based on the floor area ratio and the floor space ratio including the planned development as to whether the divided plots still offer the possibility of the desired/planned development or not, and to what extent the development is permitted.
You can only inquire about that at the municipality.
The answer from the municipality can only be given depending on the architect's planning. The municipality cannot know without the submission of the concrete development plan including the subdivision whether planning law is violated or not.
Usually, nothing is specified about that in the development plan,
The type and extent of structural use are stated first in the Building Code §9 (1). In theory, a development plan can also be drawn up without this specification, but about 8-10 criteria are usually standard; if these are missing, it is only a matter of a short time until the first lawsuit against the development plan is filed.
because the "final" parceling has already been carried out with the creation of the plan.
The development plan does not regulate the final parceling.
So go to the municipality or building authority and have the cadastral map confirmed in writing.
A competent contact person has already been provided to the original poster. One does not need to have a cadastral extract confirmed, because a cadastral extract itself is already an official product, that is a government-issued document. The subdivision of undeveloped land is (in NRW) approval-free. If a subdivision permit is required, it can (in NRW) only be applied for by a publicly appointed surveyor – other federal states have partly different regulations but operate similarly in principle.
Otherwise, as already mentioned above, a subdivision according to the Condominium Act remains. But that is not a big deal either. Here, the subdivision is basically regulated internally between the two owners.
That is neither desired nor necessary in the present case.
Best regards
Dirk Grafe