[keithwinstein]

ObNote that in standard English it's "premises," even for a single building. Some explanation here: https://ahdictionary.com/word/search.html?q=premises

[pesfandiar]

TIL. I think it's a common mistake due to overcorrection; people tend to use singular words in compound adjectives (e.g. two-year contract).

[Mindless2112]

Yes, please. "Premise" means something entirely different: "A statement that is assumed to be true and from which a conclusion can be drawn."