The sale of an adjoining vacant lot can qualify for a capital gains exclusion, but there are restrictions which are detailed in this web reference:
https://www.bza.me/?BH9Z24
This reference contains the applicable legal language (look under "Vacant Land"):
https://www.law.cornell.edu/cfr/text/26/1.121-1
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
