The notary has informed me that all the co-owners should have been summoned and taken part during the vote. is it true?
Yes…but. Special common portions are those assigned to the use or usefulness of several co-owners and not as an entirety, unlike general common portions. Decisions relating to these special common areas can be taken either during a special meeting of co-owners who use this common area, or in the context of an ordinary general meeting in which they alone take part during the vote in regard to this resolution (art. 6-2 law of July 10, 1965).
However, the existence of special common areas is subject to their express mention in the co-ownership regulations (art. 6-4 law of July 10, 1965). Failing this, they shall follow the system of general common areas. The decision to transfer part of it to one of the co-owners must then be taken during a meeting to which all the co-owners are summoned.