You don't have to buy the second parcel anymore than you have to buy any parcel. You just might find the part of your building that is on the second parcel destroyed if someone else comes along and buys that second parcel. Mind you, that other person would have to have a means of getting to that second parcel. If the only way to get to it is through your building and you deny him access to your building, then all you have to do is Adverse Possession.
Happiness is reality minus expectation