I would like to distinguish between a land-plot that is owned by a single person, and a land-plot that is owned by several unrelated people as a shared property.

I thought of using the phrase "privately-held", but, this phrase does not mean a property held by a single person (it means the opposite of "publicly-held", which has another meaning).

So, what phrases should I use to express these two opposite meanings?

I need to use these phrases in the following sentence:

"We extend the solution from ______ land-plots [owned by a single-person] to _______ land-plots [owned by several people]".