Joint tenancies require The Four Unities in order to be valid.
A true joint tenant must have perfect equality between them so that joint tenants have an equal interest in the property.
Any act that destroys one of the four unities will make the interest between the joint tenants on equal and thus will bring the joint tenancy to an end.
The four unities are as follows:
1. Unity of Interest: the interests of all joint tenants must be identical in nature, extent and duration.
2. Unity of Possession: each joint tenant must have an undivided share of the property at the same time as the other joint tenants and no joint tenant is entitled to any part of it to the exclusion of the other co-owners.
3. Unity of Title: the interests of the co-owners must be created by the same act or instrument, such as a transfer of land or a will.
4. Unity of Time: the interests of all joint tenants must be created at the same time and for the same period.
Any act that destroys one of the four unities will bring the joint tenancy to an end. For instance, if one joint tenant acquires a greater interest than his fellow joint tenants, the “unity of interest” will be destroyed, and if one joint tenant transfers his or her interest in the property to a third party, the “unity of title” will be broken and joint tenancy will be severed
In the absence of any of the four unities or in the absence of an intention to create a joint tenancy, the law presumes co-owners to hold property as tenants in common, not joint tenants. This common law presumption in favour of tenancies in common is codified by section 11(2) of the Property Law Act, RSBC 1996, c. 377 (“Property Law Act”), which provides that when land is transferred or devised in fee simple, charged, or contracted to be sold by a valid agreement for sale to two or more persons, they are tenants in common unless a contrary intention appears in the instrument. Therefore, if a joint tenancy is intended on the gift or sale of property or otherwise, the instrument must state or clearly imply such an intention.