Answer:
Method of annexation
Explanation:
Annexation is used to describe the process of joining, consolidating or pulling together into one piece. It is used in real estate to signify the merging of smaller units of property to a larger one. For example, merging a smaller piece of land( annexed to a larger one) to a larger one.
In the case above, Tim and Tina believed this would apply with the garden at the back of their house since it was already considered a small part of the property.