The expression “co-owner responsible” refers to the concept of fault as described in articles 1457 and 1458 of the Civil Code of Québec.

Thus, the mere fact that damage occurs in a co-owner’s unit does not mean s/he is “responsible”. However, in a case where the damage is caused by a thing or a person in the co-owner’s custody, the co-owner must prove that s/he is not at fault in order to be absolved of responsibility, given the presumption of article 1465 of the C.C.Q.

A declaration of co-ownership that states the contrary could not be enforced against the co-owner in question (article 1074.2 of the C.C.Q.).