As per section 3.1.1 of this document, the living space requirement for the German family reunification visa of a third-country national is 12 sqm per person:
"Without prejudice to state provisions, sufficient living space is usually deemed to be available if 12 sqm of living space are available to each family member aged above six and 10 sqm of living space for each family member aged below six. Adequate availability of the facilities (kitchen, bathrooms, lavatories) must be ensured. A shortfall of about ten percent is acceptable" — (2.4.2. General Administrative Regulation to the Residence Act)."
However, it does not state whether shared flats are allowed or not. I wonder if my wife can meet the family reunification visa requirements if I live in a shared apartment in which my private room meets the 24 square meters criteria? If positive, I wonder what the rental contract requirements of such a situation should be? Should the contract state that two persons are going to live there?
To clarify, we're not going to be living in a shared flat. I just want to save on expenses until she joins me. But she needs to enclose a proof of suitable accommodation upon her visa application.