The declaration of co-ownership includes the set of rules ensuring the efficient organization of a co-ownership. Its knowledge by the members of the board of directors and by each co-owner is essential to the proper operation of the co-ownership. This co-owners reference document is consulted, for example, in the case of work. For a promisor-buyer, the declaration of co-ownership contains a wealth of useful information regarding the conditions of use and enjoyment of the private and common portions. Hence the necessity of reading this document before buying, to avoid unpleasant surprises, especially as to the use one intends to make of his private portion.