Each Room
Some poskim maintain that an amah by amah should be made in every room of ones house. Even according to this opinion, a room which is not four amos by four amos or a hallway are not required to have a zecher lchurban. Nonetheless, the minhag is to be lenient and follow the majority of the poskim who maintain that the obligation is only in one room.
What to do?
One should peel a piece of paint or plaster from the wall. There is an opinion in the poskim which maintains that if ones wife does not want the sheetrock or plaster peeled off then one may paint a spot measuring an amah by amah a different color than the rest of the wall. However, doing so is not lchatchilah.
One who puts up wallpaper (and does not paint) is also obligated to leave a part of the wall unfinished.
Writing / Pictures of Zecher Lchurban
Some people instead of making an amah by amah as a zecher lchurban write zecher lchurban after painting a part of the wall black. Although many are opposed to this practice, one who does so does not have to be stopped. Some people hang up a nice sign or a picture of the bais hamikdosh to use instead of making a zecher lchurban. Many poskim say that doing so does not fulfill the halacha of making a zecher lchurban.
Compiled by Rabbi Moishe Dovid Lebovits who can be reached atmlebovits@kof-k.org
Reviewed by Rabbi Ben-zion Schiffenbauer Shlita
All Piskei Harav Yisrael Belsky Shlita are Reviewed by Harav Yisrael Belsky Shlita