The Shulchan Aruch (560:1) writes that after the destruction of the Beit Ha'mikdash, the Sages enacted a law requiring one who builds a house to leave an area of the wall unfinished, symbolic of our inability to dwell in perfectly finished homes while the Almighty's "home" lay in ruins. A person should leave an area on the wall the size of 1 X 1 Ama (approximately 1.5 X 1.5 feet) without plaster or paint, preferably near the entrance. If this cannot be done near the entrance, it may be done elsewhere. Only one unfinished area is required for the entire house.
In some situations, leaving a spot on the wall unfinished may cause friction between husband and wife, such as if the wife exerted herself in painting the house, and the husband then wishes to remove the paint and plaster. Chacham Bentzion Abba Shaul (Jerusalem, 1924-1998) in Or sion, Helek 3, page 276, ruled that in such a case, it suffices to paint the area a different color from the rest of the wall, rather than leave it bare.
Unfortunately, many people are not mindful of this Halacha. Rabbi Chayim Palachi (Turkey, 1788-1868), in his work "Mo'ed Le'kol Chai," in siman 10, ot 95, describes the anguish he felt over the widespread neglect of this requirement. He then cites his father's comment in his work "Avir Yaakov" testifying to the fact that people who observe this Halacha enjoy peace and stability in the home, and one should therefore make a point of observing this requirement, and leave an unfinished area on the wall in his home.
Summary: One who builds a new home must leave an area of 1.5 X 1.5 feet unfinished, preferably near the entrance. If this will cause friction between husband and wife, the area may be painted a different color, rather than be left bare.
