There is a halachah in Shulchan Aruch that there should be a reminder of the destruction of the Temple at every joyous occasion in one’s life. One application of this halachah is when one is building or renovating a house or apartment they should leave an unfinished area measuring an amah by an amah (approx. 1.5 ft x 1.5 ft) which can be seen right when one walks into the house; this area should not be newly plastered, painted, nor wallpapered.
There are some halachic authorities who are lenient and say that the unplastered area may be covered, and others who say it may not. Some say that this should be done in every room of the house, but the consensus among poskim is that leaving an unfinished area near the entrance is sufficient.
Adapted from Rav Yosef Yeshaya Braun, shlita, member of the Badatz of Crown Heights; One Minute Halacha, # 344, crownheightsconnect.com
