Q. Is the ceremony (of placing a cornerstone) recommended, and if you offer food will it become a seudas mitzvah? How about a private home?

A. Horav Shlomo Miller’s Shlit’a opinion as mentioned above (question 1096)is, that it is a proper and accepted tradition, for the reasons mentioned and if divrei Torah are said, it would be considered a seudas mitzva.
In regards to a private house, if it is being built in Eretz Yisroel, due to the mitzvah of yishuv ho’oretz, it would also be deemed a seudas mitzvah. Outside of Eretz Yisroel, there are different traditions and minhogim and one should follow his family’s established minhag. The Rov added that if the house to be build will be used to also accommodate guests in need (hachnosas orchim) or as a place where shiurim of Torah will be held, the seuda at the cornerstone ceremony would be a seudas mitzva.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit”a